CN110685600B - A Bit Adjustment Prediction Method for Geosteering - Google Patents

Abstract

The invention discloses a drill bit adjustment and prediction method for geosteering, comprising: constructing a geosteering model by using historical offset well and/or pilot hole logging data; The relative dip angle of the wellbore formation, the formation azimuth angle and the boundary distance indicated polarization values were obtained from the rate logging curve, and the geosteering model was revised to establish the initial formation model while drilling; based on the response results of the initial formation model while drilling, the model was Make corrections, invert the database according to the preset geological model, and obtain the real parameters of the formation through the fast database search method; Adjustable safety distance within. The invention can predict the stratum trend and the distance from the drill bit to the layer boundary through the conventional logging data while drilling, improve the utilization efficiency of the logging data, and guide the geosteering operation of the engineer.

Description

A Bit Adjustment Prediction Method for Geosteering

technical field

The invention relates to the technical field of oilfield development, in particular to a drill bit adjustment and prediction method for geosteering based on azimuthal gamma imaging while drilling and conventional electromagnetic wave resistivity while drilling.

Background technique

Wireline logging is always done after logging while drilling, and the tool is put into the well with a wireline for measurement, however, in some cases, such as: (1) Highly deviated wells or even horizontal wells with a well deviation of more than 70 degrees , it is difficult to measure data with wireline logging; (2) it is difficult to obtain logging data if the well wall is not in good condition, and it is difficult to obtain logging data; (3) under normal circumstances, logging is performed after the well is drilled. There are some differences between these parameters and the original formation parameters. With the massive exploitation of oil, the number of integrated oil and gas reservoirs gradually decreased, and the complex and difficult-to-break oil and gas reservoirs gradually increased. At the end of the 20th century, in order to meet the development needs of the petroleum industry, especially to improve drilling efficiency and oil reservoir recovery, water Horizontal well drilling and geosteering technology have gradually developed. In the early 1980s, with the maturity of directional well technology and the application of new downhole tools and instruments, horizontal well drilling entered a period of vigorous development. Logging while drilling has become an important means of reservoir evaluation for horizontal wells, and it is also a key technology to complete horizontal well drilling design, real-time well site data acquisition, interpretation and field decision-making, and to guide geosteering drilling.

Due to the short formation drilling time of LWD, the logging curve can not only reflect the real-time stratum change, but also provide a variety of detection depth curves. The LWD data is rich in information and rich in logging curves. Therefore, it is widely used in horizontal well geosteering, post-drilling interpretation and evaluation. At the same time, logging while drilling tools are increasingly abundant. Currently, LWD can measure more than 30 parameters (resistivity, gamma, density, acoustic wave, seismic, nuclear magnetic, etc.) Correspondingly, the outer diameter of the tool is 44.5-216.0mm, which basically meets the needs of various directional wells. Driven by the timeliness and high profits of LWD, the world's major petroleum technology service companies have strengthened the research and development of drilling-while-drilling technology in recent years.

In the prior art, the formation model is usually established according to the logging data collected in real time, so as to construct the relationship between the wellbore trajectory and the formation position, and use it as the data basis of the geosteering technology. In the actual logging while drilling process, due to the huge amount of measured data collection and processing, this method that requires real-time construction of the formation model will make the processing efficiency of logging data low, thus affecting the performance of geosteering operations. Accuracy and timeliness. In addition, the calculation method for the specific drill steering adjustment is rarely involved.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a method for predicting the adjustment of a drill bit for geosteering. The method includes the following steps: Step 1, performing a fast inversion on the standardized logging data of offset wells and/or pilot wells process, and divide the stratigraphic horizons according to the inversion results to construct a geosteering model; step 2, use the real-time measurement of the azimuth-while-drilling gamma imaging logging curve and the electromagnetic wave resistivity logging curve obtained during the logging-while-drilling operation data, and obtain corresponding MWD parameters including the relative dip angle of the wellbore formation, formation azimuth and boundary distance indicating polarization value; Step 3, combine the MWD parameters, correct the geosteering model in real time, and establish initial formation model while drilling; step 4, based on the response result of the initial formation model while drilling, inversion database according to a preset geological model, and further correcting the initial formation model while drilling through a quick database search method to obtain the real formation parameters, the real formation parameters include the relative dip angle of the wellbore formation, the distance from the measurement point to the formation boundary, and the formation layer thickness; step 5, according to the real formation parameters, carry out iso-dip angle extension for the formation that has not been drilled, and predict the formation The change of the interface along the axis of the horizontal well to be drilled and the safety distance of the bit adjustment to guide the geosteering operation.

Preferably, the step 5 further includes: acquiring the drill bit inclination angle and calculating the formation apparent dip angle; predicting that the formation resistivity and formation thickness outside the detection range are within the wellbore according to the formation apparent dip angle and the real formation parameters. According to the 2D sectional view of the stratum, the distance between the drill bit and the measurement point and the direction of the drill bit, predict the position of the layer boundary of the stratum that has not been drilled, and further determine the drill bit. The distance to drill out of the target layer.

Preferably, the step 4 further comprises: comparing the response result of the initial formation model while drilling with the measured data, and using a gradient descent method to obtain a model correction amount corresponding to the initial correction initial formation model while drilling; The model correction amount is obtained, the logging response of the initial model while drilling stratum after the preliminary correction is searched from the geological model inversion database, and the logging response obtained by checking the database is compared with the measured data, and the second correction is obtained. The initial stratum-while-drilling model is obtained, and the second-corrected stratum-while-drilling model is further used as an inversion result to obtain the corresponding real stratum parameters.

Preferably, in the fourth step, according to the formation characteristic parameters of the area where the horizontal well to be drilled in the logging-while-drilling operation and the parameters of the measurement-while-drilling instrument, a classified forward modeling geological simulation model library is established; The numerical simulation algorithm performs numerical forward simulation calculation on each type of parameters in the classified forward modeling geological simulation model database, obtains the relationship between the formation model-electromagnetic wave resistivity curve-boundary distance, and forms the geological model inversion database.

Preferably, the first step further includes the following steps: acquiring the formation resistivity and formation structure parameters obtained after the fast inversion processing, using the inversion method to divide the inversion results into formation horizons, determining the formation boundary and displaying the formation horizons The horizon division result of the horizontal and depth correspondence; the geosteering model is obtained by taking the log data of the offset wells and/or pilot wells that have undergone standardized preprocessing as initial parameters and combining the horizon division results.

Preferably, in the step of dividing the inversion results into stratigraphic horizons by using the inflection point method, determining the stratigraphic horizons, and displaying the horizon dividing results of the horizontal and depth correspondence of the stratigraphic horizons, it also includes: if there are multiple offset wells, then It is necessary to stratify each adjacent well to obtain the stratum layer division corresponding to the horizontal well to be drilled and the well position coordinates of each adjacent well; By comparing and linking, the layer division result showing the horizontal and depth correspondence of the entire formation horizon of the horizontal well to be drilled is obtained.

Preferably, in the second step, the relative dip angle of the wellbore formation is obtained by the following steps: using the inflection point method to determine the azimuth gamma imaging data crossing layer according to the azimuth gamma imaging logging curve acquired in real time interface position depth; according to the position depth of the azimuth gamma imaging data crossing the layer interface, calculate the elevation difference of the azimuth gamma imaging data; The elevation difference of the azimuthal gamma imaging data is used to extract the relative dip angle of the wellbore formation from the azimuthal gamma imaging logging curve while drilling.

Preferably, the third step further includes: determining the number of formation layers, the resistivity of each layer and the lateral change of layer thickness according to the response data of the geosteering model and the layer division result; The relative dip angle of the wellbore formation extracted from the drilling azimuth gamma imaging logging curve is corrected, and the relative dip angle of the wellbore formation obtained in the geosteering model is corrected; The obtained boundary distance indicates the polarization value, calculate the distance from the measurement point to the formation boundary surface, and further perform depth correction on the corresponding relationship between the horizontal and depth of the formation horizon in the geosteering model that has completed the correction of the relative dip angle of the wellbore and formation, and establish the The initial model of the formation while drilling is described.

Preferably, in the step of further determining the distance at which the drill bit drills out of the target layer, according to the two-dimensional cross-sectional view of the stratum, the distance from the drill bit to the measurement point, and the direction of the drill bit, predicting the position of the layer boundary of the stratum that has not been drilled at an equal dip angle, and further determining the distance from the drill bit to the target layer, When the inclination angle of the drill bit is less than 90 degrees, the method further includes: calculating the distance between the drill bit and the upper boundary of the formation by using the real formation parameters including the relative inclination angle of the wellbore formation and the distance from the measurement point to the formation boundary, so as to obtain the distance between the drill bit and the formation boundary. The distance from the lower boundary of the formation is used to determine the position of the drill bit in the target layer; according to the distance between the drill bit and the lower boundary of the formation, predict the distance that the bit drills out of the lower boundary of the formation, and use it as the safety distance for the adjustment of the drill bit.

Preferably, in the step of further determining the distance at which the drill bit drills out of the target layer, according to the two-dimensional cross-sectional view of the stratum, the distance from the drill bit to the measurement point, and the direction of the drill bit, predicting the position of the layer boundary of the stratum that has not been drilled at an equal dip angle, and further determining the distance from the drill bit to the target layer, When the inclination angle of the drill bit is greater than 90 degrees, the method further includes: calculating the distance between the drill bit and the lower boundary of the formation by using the real formation parameters including the relative inclination angle of the wellbore formation and the distance from the measurement point to the formation boundary, so as to obtain the distance between the drill bit and the formation boundary. The distance from the upper boundary of the formation is used to determine the position of the drill bit in the target layer; according to the distance between the drill bit and the upper boundary of the formation, the distance that the drill bit drills out of the upper boundary of the formation is predicted and used as the safety distance for the adjustment of the drill bit.

Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

The present invention can predict the stratum trend and the distance from the drill bit to the stratum boundary through azimuthal gamma imaging and conventional electromagnetic wave resistivity logging while drilling data, which is an urgently needed data processing technology in the process of geosteering. The advantages of well data detection and comprehensive utilization improve the utilization efficiency of logging data, and guide the steering engineer to adjust the angle of the drill bit in the process of geosteering, thereby guiding the geosteering.

Other advantages, objects, and features of the present invention will be set forth in the specification to the extent that follows, and will be apparent to those skilled in the art based on a review of the following, or may be Guidance is gained from the practice of the present invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the description and claims hereof as well as the appended drawings.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and together with the embodiments of the present invention, are used to explain the present invention, and do not constitute a limitation to the present invention. In the attached image:

FIG. 1 is a step diagram of a method for predicting drill bit adjustment for geosteering according to an embodiment of the present invention.

Fig. 2a is a resistivity wellbore correction chart of the method for predicting the adjustment of bit adjustment for geosteering according to an embodiment of the present invention.

FIG. 2b is a resistivity and dielectric correction chart of the method for predicting the adjustment of a drill bit for geosteering according to an embodiment of the present invention.

FIG. 3 is an example diagram of an offset well inversion result of the drill bit adjustment prediction method for geosteering according to an embodiment of the present invention.

FIG. 4 is a schematic diagram of a geosteering model of the drill bit adjustment prediction method for geosteering according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of the response of the electromagnetic wave resistivity curve synthesis while drilling indicating layer boundary distance signal (Peak value signal) of the drill bit adjustment prediction method for geosteering according to an embodiment of the present invention.

6a is a schematic diagram of the location of the bit and the distance between the bit and the formation interface in geosteering when the inclination angle of the bit is less than 90° in the method for predicting bit adjustment for geosteering according to an embodiment of the present invention.

6b is a schematic diagram of the location of the bit and the distance between the bit and the formation interface in geosteering when the inclination angle of the bit is greater than 90° in the method for predicting bit adjustment for geosteering according to an embodiment of the present invention.

7 is a cross-sectional view of a real-time inversion of geosteering for a method for predicting drill bit adjustment for geosteering according to an embodiment of the present invention.

Detailed ways

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so as to fully understand and implement the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects. It should be noted that, as long as there is no conflict, each embodiment of the present invention and each feature of each embodiment can be combined with each other, and the formed technical solutions all fall within the protection scope of the present invention.

The embodiment of the present invention aims to form a geological model inversion database that can be queried by applying an analytical solution simulation algorithm, and uses the logging data of offset wells and pilot wells to obtain the formation parameters and divide the formation horizons through the inversion method. Steering model, further use azimuth gamma imaging while drilling and conventional electromagnetic wave resistivity to establish the correction value of the geosteering model, and correct the steering model as the initial model of formation inversion. Then, taking the initial model as the starting point, the gradient descent method is used to calculate the model correction amount, and by developing a fast database search algorithm, the simulated response of the corrected model and the log response residual of the measured data are compared, and the gradient descent method is used to modify the model according to the residual conditions. , until the residuals between the model response and the logging response are small enough to output the inversion information such as the relative dip angle and boundary distance of the wellbore formation. Guiding geosteering.

FIG. 1 is a step diagram of a method for predicting drill bit adjustment for geosteering according to an embodiment of the present invention. As shown in Fig. 1, in step S110 (step 1), the standardized logging data of offset wells and/or pilot wells are subjected to rapid inversion processing, and the formation layers are divided according to the inversion results to construct a geosteering model .

In step S110 (step 1), based on the historical logging data of the offset wells and/or pilot wells collected before the standardization and pre-drilling, the preprocessing results are subjected to rapid inversion processing of formation logging parameters to obtain The formation resistivity parameters and the formation structure parameters including the formation horizon division results are used to divide the inversion results into the formation horizons, determine the stratigraphic layer boundaries, and display the horizon division results of the horizontal and depth correspondence between the formation horizons, and further , taking the historical logging data of offset wells and/or pilot wells after standardized preprocessing as initial parameters, and combining the results of horizon division, a geosteering model is constructed. Specifically, this process includes the following steps:

First, (step S1101 ) the historical logging data of offset wells and/or pilot wells collected before drilling needs to be subjected to standardization processing including erroneous data elimination, missing data supplementation, and correction of non-strata influencing factors in sequence.

In error data elimination, the following error data evaluation indicators are established:

Among them, Er _k is the error index function of the k-th sampling point on any logging curve of the offset and pilot wells, and Ra _k and Ra _i represent the k-th and i-th measurement points of the offset and pilot wells, respectively Logging response, m is the window length of the error data evaluation index, when the error index function satisfies any of the following conditions, the current logging data is judged as error data:

Next, delete the erroneous data, delete the logging response of the position corresponding to the erroneous data, and set the position data as missing data.

Further, the historical logging data formed after the deletion of the erroneous data adopts the linear smoothing method of multi-point sampling to supplement the missing point data, and the above method is expressed by the following expression:

表示重采样后第i个采样点取值。Among them, T _i represents the logging value of the i-th measurement point, T _i+k represents the log value of the i+k-th measurement point, i and k are the subscripts of the recorded measurement values, m represents the length of the smoothing window, and A _i represents the The weighting factor of the i-th point,

Indicates the value of the i-th sampling point after resampling.

Finally, the log data supplemented by missing data is corrected for non-strata factors. In this example, the calibration sampling plate method is used in this process, and the calibration processes for non-strata factors such as borehole calibration, eccentricity calibration and dielectric constant calibration are successively performed. Fig. 2a is a resistivity wellbore correction chart of the method for predicting the adjustment of bit adjustment for geosteering according to an embodiment of the present invention. FIG. 2b is a resistivity and dielectric correction chart of the method for predicting the adjustment of a drill bit for geosteering according to an embodiment of the present invention. As shown in Fig. 2a and Fig. 2b, the abscissa is the resistivity logging response, and the ordinate is the correction coefficient. When the plate is calibrated, first find the horizontal axis position of the plate corresponding to the current measurement value through the abscissa, and make a straight line on it to intersect the curve in the plate, and the ordinate value corresponding to the intersection point is the correction coefficient. The product of the measured value and the correction factor is the resistivity log response corrected for non-formation factors. In this way, the normalization processing of the log data of the offset well and/or pilot hole is completed to obtain the undisturbed formation resistivity parameter.

Then (step S1102) after the standardization preprocessing is completed, perform full-parameter inversion on the standardized data, obtain the formation electrical parameters (including the resistivity of the invasion zone, the resistivity of the original formation, etc.) through the inversion, and use the inflection point The inversion results are divided into stratigraphic horizons using the method to determine stratigraphic horizons and horizon partitioning results showing the horizontal and depth correspondence between stratigraphic horizons, so as to obtain the corresponding stratigraphic structure parameters (including: invasion depth, stratigraphic horizon location, etc.) .

In this example, the inflection point method is used to divide the normalized historical logging data, and the difference is used to replace the differential. The well depth section is divided into the same formation, and the place where the resistivity changes sharply (the second derivative of the logging curve is 0) is determined as the formation interface, that is, the inflection point position where the inflection point function is equal to 0 is determined as the formation boundary. Among them, the second-order difference equation of the logging curve is expressed by the following expression:

Among them, x represents the sampling point position of the logging curve, f ₁ (x) represents the inversion response result of the normalized and preprocessed logging data of the offset well and/or pilot well when the sampling point location is x, f ₁ (xh), f ₁ (x+h) represent the forward modeling response results of the log data of the offset well and/or pilot well that have been standardized and preprocessed at xh and x+h, respectively, and h represents Step size, g ₁ (x) is the second-order difference value of the inversion response result. The value of x when g ₁ (x)=0 is the interface position.

The resistivity value in the log data of the offset and/or pilot wells that have undergone standardized preprocessing is used as the initial value of formation resistivity, combined with the horizon division results of the inflection point method (the above-mentioned offset and/or pilot well logging data Formation interface analysis results), to establish the initial model for the rapid inversion of offset wells.

FIG. 3 is an example diagram of an offset well inversion result of the drill bit adjustment prediction method for geosteering according to an embodiment of the present invention. As shown in Fig. 3, the initial model for rapid inversion of offset wells includes: plotting invasion profile from inversion results, well depth corresponding to measurement points, invasion radius, inversion results, apparent resistivity, neutron density and porosity.

Next, the objective function is established by comparing the response data of the initial model for the rapid inversion of the offset wells and the residual sum of squares of the historical logging data of the offset wells and pilot wells:

Among them, r represents the inversion results of the initial model of the offset well rapid inversion; R represents the independent variable vector; m represents the number of unknowns; n represents the number of forward response curves; x represents the model parameters (including resistivity, layer thickness, etc.) , boundary distance, invasion depth, borehole diameter, etc.); f(x) represents the objective function, and T represents the matrix transposition.

The Jacobian matrix of the objective function is solved by the gradient descent method to form a system of Jacobian linear equations, and the steepest descent direction of the objective function is calculated by solving the equation system, which is expressed by the following expression:

Calculate the gradient of the objective function according to the following formula:

是微分算子，r_i(x)是模型参数x对应的响应函数第i个分量。求解目标函数需要先在最速下降方向上确定步长h；进一步根据求得邻井快速反演初始模型改变方向和改变步长，确定该模型的改变量，改变模型，完成一次模型更新，进而，通过设置循环终止条件，循环调用模型更新过程，直至满足循环终止条件，从而构建地质导向模型，得到地层测井参数。where x is the model parameter, r(x) is the response function corresponding to the model parameter x, Y(x) is the Jacobian matrix of r(x), g(x) is the gradient function,

is the differential operator, and ri (x) is the _ith component of the response function corresponding to the model parameter x. To solve the objective function, it is necessary to first determine the step size h in the direction of the steepest descent; further, according to the obtained offset well rapid inversion initial model change direction and change step size, determine the change amount of the model, change the model, and complete a model update, and then, By setting the cycle termination conditions, the model update process is called cyclically until the cycle termination conditions are met, so as to build a geosteering model and obtain formation logging parameters.

It should be noted that, in the process of stratum level division, if the horizontal well to be drilled has multiple offset wells, each offset well needs to be layered according to the same method to obtain the well positions of the horizontal well to be drilled and each offset well. The division of the stratum corresponding to the coordinates. Then, according to the coordinate distribution information of the adjacent wells, compare and link each adjacent well according to the horizon division of the same depth, and obtain the horizon division result showing the horizontal and depth correspondence of the entire formation horizon of the horizontal well to be drilled. . Furthermore, the interface between wells is connected to the same horizon interface in different offset wells through the linear difference method, so as to obtain the corresponding stratigraphic profile.

Finally, a 3D steering model is constructed and applied to the 2D profile based on the analysis results of the stratigraphic interface of the logging data of the above-mentioned offset wells and/or pilot wells, and the results of the horizon comparison of the offset wells or the relative dip angle of the wellbore strata. Display and complete the establishment of the geosteering model, from which the position of the stratum boundary, the target layer (the position of the wellbore to be logged), the logging information of the upper and lower strata, the relative dip angle of the wellbore stratum, etc. can be obtained, so as to obtain the entire stratum horizon. Horizontal and depth correspondence. FIG. 4 is a schematic diagram of a geosteering model of the drill bit adjustment prediction method for geosteering according to an embodiment of the present invention. As shown in Figure 4, the model shows the position of the formation interface (at the left of Figure 4, where the horizontal parallel line is the determined formation boundary), the target layer and formation resistivity information, and the curve is the completion of the horizontal well design wellbore trajectory.

In step S110, according to the pre-drilling historical logging data of the offset well and/or the pilot hole collected before drilling, and the inherent geological parameters of the area where the pilot hole is located (including: formation resistivity, formation anisotropy, layer thickness , boundary distance, formation permittivity, formation water salinity, rock porosity and density, natural gamma, etc.), first perform a rapid inversion of the initial model for the adjacent well, and then use the history of the adjacent well and pilot well. The logging data corrects the initial model of the rapid inversion of the offset well, thereby completing the construction of the geosteering model. This method has the advantages of convenience, feasibility and high calculation accuracy: on the one hand, there is no need to rebuild the initial steering model during the logging while drilling process, and only the historical logging data is used to complete the model construction in advance, which improves the work of logging while drilling. On the other hand, considering the influence of the environmental background in LWD, the parameters of the model construction are more comprehensive, the accuracy of the logging response is improved, it is more in line with the actual application environment of geosteering operations, and the accuracy of bit adjustment is increased. .

After the establishment of the above-mentioned geosteering model is completed, step S120 is entered. In step S120 (step 2), using the azimuth-while-drilling gamma imaging logging data obtained in real time during the logging-while-drilling operation and the measured data of the electromagnetic wave resistivity logging curve while drilling, the corresponding data including the borehole formation relative Dip, formation azimuth and boundary distance indicate MWD parameters of polarization values to determine the formation horizon where the horizontal well to be analyzed is located. Specifically, using the azimuth gamma imaging logging curve detected in real time, the inflection point method is used to calculate the elevation difference of the azimuth data, and the azimuth angle and the relative dip angle of the borehole formation obtained based on the elevation difference of the azimuth data are extracted; The resistivity logging curve detected in real time is used to synthesize the boundary indicating polarization value (Peak value) signal by using the resistivity polarization effect of conventional electromagnetic wave while drilling.

The sub-steps included in step S120 will be described in detail below.

First, (step S1201 ) according to the real-time acquisition of the detected azimuthal gamma imaging logging curve while drilling and the change of the azimuthal gamma imaging data, the inflection point method is used to calculate the depth of the azimuthal gamma imaging data through the layer interface. The inflection point curve of the azimuth-while-drilling gamma imaging logging curve is defined by the following expression:

为求导数符号。进一步，拐点曲线相应的离散公式为：Among them, t represents the depth value of the measurement point, G(t) represents the inflection point function value of the azimuth-while-drilling gamma imaging logging curve at t, and f ₃ (t) represents the azimuth-while-drilling gamma at the test point t. Imaging log measurements,

for the derivative symbol. Further, the corresponding discrete formula of the inflection point curve is:

Among them, △ represents the sampling interval, f ₃ (t+△) represents the response data of the geosteering model at t+Δ, and f ₃ (t-△) represents the response data of the geosteering model at t-Δ. From the definition formula of the inflection point, it can be seen that t is the interface position by setting G(t)=0, and the inflection point is actually the position where the second derivative of the random signal f ₃ (t) is equal to zero. It reflects the dynamic nature of the well logging curve. Therefore, under the inflection point curve defined here, when the inflection point curve is equal to 0, it is the place where the response curve of the geosteering model changes most violently, that is, the stratum interface with different lithology, thus determining the interlayer interface of the measured azimuth gamma imaging data. position to further determine its depth.

Then, it proceeds to step S1202. The corresponding azimuth gamma imaging data cross-layer interface position depth and orientation information are obtained from the above-mentioned azimuth gamma imaging data cross-layer interface position data, and the azimuth gamma imaging data elevation difference is calculated based on this. Specifically, when the instrument passes through the layer interface at a certain inclination angle, the azimuth gamma measurement curve encounters the boundary surface at different times in different directions, and the corresponding depths are also different. Therefore, the 360° azimuth expansion curve of the azimuth-while-drilling gamma imaging logging curve satisfies the cosine distribution, and the period is 2π. Here, assuming that the cosine function equation is y=Acos(αx+θ)+b, the cosine can be obtained by bringing the logging response of the azimuth measurement (the depth of the azimuth gamma imaging data through the interface position) and the corresponding azimuth into the formula The functional unknowns (A, α, θ, and b), in particular the parameter A representing the amplitude of the cosine curve, which is equivalent to the azimuthal gamma imaging data elevation difference. Further, since the cosine amplitude is equivalent to the elevation difference H of the azimuth gamma imaging data, let H=A. When the H value is greater than 0, it means that the low side of the azimuth tool encounters the formation interface first, and the tool passes through the layer interface with an angle less than 90 degrees relative to the normal of the layer interface; when H is less than 0, it means the high side of the azimuth tool The layer interface is encountered first, and the gesture with the included angle between the instrument and the interface normal greater than 90 degrees passes through the layer interface.

Next, (step S1203), since the azimuth gamma imaging is closely related to the curve detection depth when extracting the relative dip angle of the borehole formation, the corresponding detection depth correction should be performed first according to the detection characteristics of the instrument. Specifically, based on the obtained caliber curve of the current pilot hole and the detection depth of the azimuth gamma imaging instrument, the detection depth of the azimuth gamma imaging instrument at the current measurement point is obtained, and further combined with the above-mentioned elevation difference of the azimuth gamma imaging data, the arc tangent function is used. , calculate the relative angle between the normals of the borehole formation interface (that is, the relative dip angle of the borehole formation), that is, extract the relative dip angle of the borehole formation from the azimuth-while-drilling gamma imaging logging curve. Among them, the detection depth of the current measurement point azimuth gamma imaging instrument is expressed by the following expression:

_Del =DH+2*DOI _EFF (11)

Among them, D _el represents the detection diameter, DH represents the diameter of the pilot hole; DOI _EFF represents the detection depth of the instrument. The value of the electrical diameter _Del is related to the properties of the instrument itself, and satisfies the condition of _Del >DH. Typically, the depth of detection DOI _EFF is independent of the true borehole diameter, depending on the medium background value and formation absorption, high-gamma formations may be deeper than low-gamma formations.

Finally, the calculation formula of the relative dip angle of the wellbore formation extracted from the azimuth-while-drilling gamma imaging logging curve is expressed by the following expression:

In Equation (12), DIP represents the extracted wellbore-formation relative dip.

When calculating the formation azimuth, since the azimuth gamma imaging 360° logging development plane satisfies the cosine function, and the period is 2π, the measured value of the azimuth gamma imaging logging data is calculated by the analytical method according to this property (the following cosine x) in the curve satisfies the initial phase of the cosine function, thereby obtaining the formation azimuth. Specifically, the equation defining the cosine curve here is:

y=A ₀ cos(ωx-β)+y ₀ (13)

(n＝2或n＝4)，β为初始相位(地层方位角)，yi表示方位伽马成像测井数据的测量值，n表示方位测量个数。至此余弦方程中只有A₀与β未知，因此将高边、低边方位测井值带入余弦曲线方程，得：Among them, ω represents the period of the cosine curve, that is, the image width of the expanded graph, y ₀ represents the ordinate offset of the gamma value (gamma mean value),

(n=2 or n=4), β is the initial phase (formation azimuth), yi represents the measurement value of the azimuth gamma imaging logging data, and n represents the number of azimuth measurements. So far, only A ₀ and β are unknown in the cosine equation, so the high-side and low-side azimuth logging values are put into the cosine curve equation, and we get:

Solving the above system of equations, we get:

Among them, the relative dip angle of the wellbore formation extracted above is substituted into φ, and further, the formation azimuth angle β is obtained.

Next, the calculation process of the boundary distance indicating polarization value will be described. From the electromagnetic wave resistivity logging curves transmitted in real time, select several curves with high logging quality and different detection depths, and use the numerical simulation algorithm in the analytical method to synthesize the indicator layer boundary distance signal (Peak value signal) . FIG. 5 is a schematic diagram showing the response of the electromagnetic wave resistivity curve while drilling synthetically indicating layer boundary distance signal (Peak value signal) of the drill bit adjustment prediction method for geosteering according to an embodiment of the present invention. As shown in Figure 5, the horizontal axis represents the distance between the measurement point and the layer interface, the vertical axis represents the response of the boundary distance indicating polarization value signal (Peak value signal), and different curves represent the boundary distance indicating polarization value under different resistivity contrasts Signal.

The calculation of layer boundary distance signal (peak value signal) is obtained by defining the polarization value by comparing the response of electromagnetic wave resistivity logging curves while drilling in the same formation in vertical well and inclined well logging environment. The boundary distance indicates the polarization value is calculated using the following expression:

Among them, Peak represents the magnitude of the polarization value indicated by the boundary distance, Ra represents the apparent resistivity, Dip represents the above-mentioned relative angle between the borehole and the formation interface normal (DIP), and θ represents a certain relative angle between the borehole and the formation interface normal. An angle value, Ra | _Dip=θ represents the apparent resistivity measured when the normal angle between the borehole and the formation interface is θ (that is, the response value of the electromagnetic wave resistivity logging curve while drilling in the deviated well logging environment), Ra | _Dip=0 means the apparent resistivity measured when the normal angle between the borehole and the formation interface is 0 (that is, the response value of the electromagnetic wave resistivity logging curve while drilling in the vertical well logging environment).

Referring to Figure 5 again, it can be seen that the closer the measurement point is to the layer boundary, the greater the response amplitude of the Peak value signal. According to this property, the polarization value Peak indicating the boundary distance can be obtained, thereby determining the layer where the horizontal well drill bit is located. Further, the boundary distance may be calculated, and then step S130 is entered.

In step S130, based on the inversion results in the above-mentioned geosteering model, combined with the measurement-while-drilling parameters including the relative dip angle of the wellbore formation, the formation azimuth angle and the boundary distance indicated polarization value extracted from the measured azimuth gamma imaging data, Further, based on the distance from the measurement point to the boundary calculated by the boundary distance indicator polarization value, combined with the above measurement while drilling parameters and the comparison and matching of the model forward curve and the measured data, the geosteering model was corrected in real time, and the initial formation model while drilling was established.

Specifically, first, according to the inversion results (response data) of the geosteering model, through the horizon correspondence between adjacent wells and the horizon where the horizontal well bit is located (the horizon where the horizontal well to be analyzed is located), further, determine the modeling stratigraphy The number of layers, the resistivity of each layer, and the layer thickness change in the horizontal direction.

Then, the relative inclination angle of the wellbore formation in the obtained geosteering model is corrected by using the relative inclination angle of the wellbore formation extracted from the real-time azimuth-while-drilling gamma imaging logging curve.

Then, using the electromagnetic wave resistivity logging curve detected in real time, with the aid of the boundary distance indicating polarization value and numerical simulation algorithm in the established geosteering model, the boundary distance indicating signal in the measured curve is defined and synthesized. Further, according to the boundary distance indicating polarization value (the magnitude of the boundary distance indicating signal) obtained through the electromagnetic wave resistivity logging curve while drilling, the distance from the measurement point to the formation boundary is calculated. Based on this, the relative dip angle correction of the wellbore formation will be completed. The horizontal and depth correspondence between the stratum horizons in the geosteering model and the stratigraphic horizons corresponding to the current measurement points are corrected in depth, and the geosteering model is updated in real time, thereby completing the establishment of the initial stratigraphic model while drilling.

Next, step S140 will be described. In this step, based on the response results of the above-mentioned initial formation model while drilling, according to a preset geological model inversion database, and through a pre-created fast database search algorithm, the initial formation model while drilling is further revised to obtain the real formation parameters, wherein, The real formation parameters include the relative dip angle of the wellbore formation, the distance from the measurement point to the formation boundary, and the formation thickness.

First, the construction process of the geological model inversion database is described in detail.

Due to the large amount of calculation and slow calculation speed of forward modeling in the horizontal well environment while drilling, the application of electromagnetic wave forward and inversion while drilling in geosteering is restricted. The existing steering technology is only based on measured values and relevant experience Qualitatively determine the position of the wellbore in the formation, the adjustment of the drill bit depends on the shallow detection gamma logging while drilling data, and the deep detection resistivity logging data only plays the function of verifying the conclusion, and does not give full play to the advantages of the electromagnetic wave resistivity instrument while drilling .

The invention solves the bottleneck problem of calculation amount and calculation speed by establishing a classification and forward modeling geological simulation model, and develops rapid database inversion and inversion, and utilizes the logging curve of electromagnetic wave resistivity while drilling with deep detection function for geosteering, which can predict the formation in advance. The existence of the interface, through the inversion method, can accurately calculate the distance from the measurement point to the layer boundary, and realize the transformation of geosteering from qualitative judgment to quantitative calculation, and from reservoir steering to reservoir steering.

In the process of constructing the geological model inversion database, it is necessary to first obtain the formation characteristic parameters of the area where the horizontal well to be drilled in the logging while drilling operation and the parameters of the measurement while drilling instrument, which are used as the background data and fully consider the following formation while drilling. The initial model includes response results such as the relative dip angle of the wellbore formation, formation resistivity Rt, upper and lower formation resistivity (RT1, RT2), and the relative position relationship between the wellbore and formation. The index results are classified, and finally the classification and forward modeling geological simulation model library is formed.

Specifically, combined with the characteristics of the targeted oilfield blocks, the parameter dimensions of the formation model are determined, the multi-dimensional model parameters are changed in different dimensions, the change step is set, and the index of the geological model fast inversion database is established. The setting process is as follows.

For the block applied by the classification forward modeling geological simulation model library, collect the geological parameters of the block, and use the block stratigraphic parameters to guide the setting of the classification forward modeling geological simulation model library. Table 1 is a specific example of formation parameters of a certain block.

Table 1 Block formation parameters

minimum maximum value Remarks (unit) common range Well diameter range 8 15 in 8.5～13.25 Mud Resistivity 0.02 0.5 ohm.m 0.02～0.05 Mudstone resistivity 0.5 10 ohm.m 3 to 6 Oil (gas) layer resistivity 1 200 ohm.m 3 to 50 Water layer resistivity 0.2 3 ohm.m 0.2～2 Formation porosity (reservoir) 5 50 pu 6～36 Formation water resistivity 0.04 0.3 ohm.m Salinity: 15000-35000ppm Well inclination angle of target layer 0 98 Horizontal well is 90° Permeability (reservoir) 0.1 2000 mD

Among them, the classified forward modeling geological simulation model library includes instrument parameters such as instrument radius 7in, coil radius 6.75in, 6 transmitters and 2 receiver coils, and the distances between the transmitter coil and the midpoint of the instrument are 15in, -15in, 25in, -25in, 45in, - 45in, the spacing between the receiving coils is 6in; the relative permeability of the drill collar is 1, the drill collar is a good conductor, the instrument operating frequency is 2MHz and 500KHz; the hole size varies from 6in to 17in, and the step interval is 0.5in; the mud resistivity is 0.02ohm.m～ 3ohm.m change, step interval 0.01ohm.m; including formation parameter resistivity 0.1ohm.m～2000ohm.m change, step interval 0.1ohm.m; anisotropy coefficient 1～4, interval 0.2; layer thickness change 0.1m～20m, the step interval is 0.2m; the boundary distance varies from 0m to 10m, and the step interval is 0.1m; the relative permittivity varies from 1 to 300, and the step interval is 1. Finally, the classified forward modeling geological simulation model library is arranged in the order of well diameter - mud - layer thickness - boundary distance - anisotropy coefficient - dielectric constant - formation resistivity, and the data of each dimension is sorted in increasing order.

In order to construct and call the geological model library accurately and quickly, it is necessary to construct the index of the geological model library. When constructing the index, the factors are classified according to the influencing factors in sequence, and then subdivided in each category. For example, the formation model can be divided into single-layer model, two-layer model, three-layer model, etc.; for example, in the two-layer model, we can divide into sub-categories: anisotropic formation is one type, isotropic Strata is one type; in isotropic formations, we can divide into sub-categories: vertical well is one type, 30 degrees is one type, 60 degrees is one type, 90 degrees is one type, etc. .

Next, based on Maxwell's equations, the numerical simulation algorithm of the analytical solution method (analytical solution numerical simulation algorithm) is used to carry out numerical forward simulation calculation for each type of parameters in the classified forward modeling geological simulation model library, and the corresponding relationship between the model parameters and the logging response is established. , and use the relationship between the logging response and the boundary distance (that is, the relationship between the boundary distance indicating polarization value and the corresponding boundary distance), and further save the calculation results according to the above classification sequence, and obtain the formation model-electromagnetic wave resistivity curve-boundary distance relationship to form a database for rapid inversion of geological models.

方向单位磁偶极子在均匀各向异性介质中产生的Hertz势可用如下表达式表示：Among them, the numerical simulation algorithm of the analytical solution method includes the following steps: when the distance between the transmitter coil and the receiver coil of the instrument is large and the coil radius is small, the coil can be equivalent to a point, so the magnetic dipole theory can be used to replace the induction coil. Let the variation relationship of the unit magnetic dipole source with time be exp(iωt), where ω is the angular frequency, and it is assumed that the position coordinate of the source point in the formation Cartesian coordinate system (the horizontal plane is the xy plane) is r _t = (x _t , y _t , z _t ), the position coordinates of the field point are r=(x, y, z), then

The Hertz potential generated by a directional unit magnetic dipole in a homogeneous anisotropic medium can be expressed by the following expression:

μ_b表示均匀介质磁导率，σ_hb表示均匀各向异性介质的水平复电导率，i为虚数单位，ω为角频率。in,

μ _b is the magnetic permeability of the homogeneous medium, σ _hb is the horizontal complex conductivity of the homogeneous anisotropic medium, i is the imaginary unit, and ω is the angular frequency.

After transformation, equation (17) can be expressed as the following Sommerfeld integral form:

J_v表示v阶Bessel函数，J₀表示0阶Bessel函数。

方向单位磁偶极子在均匀各向异性介质中产生的Hertz势可用如下表达式表示：where λ represents the integral variable,

J _v represents the v-order Bessel function, and J ₀ represents the 0-order Bessel function.

The Hertz potential generated by a directional unit magnetic dipole in a homogeneous anisotropic medium can be expressed by the following expression:

表示各向异性系数，σ_vb表示垂直电导率、k_v ²＝-iωμ_bσ_vb。经推导式(19)、式(20)可以分别表示如下表达式Sommerfeld积分形式：in,

represents anisotropy coefficient, σ _vb represents vertical conductivity, k _v ² =-iωμ _b σ _vb . After deriving equations (19) and (20), the following expressions can be expressed as the Sommerfeld integral form:

in,

Since the relationship between the electromagnetic field and the Hertz potential can be expressed by the following expression:

表示均匀各向异性介质的电导率张量，H表示Hertz势。将式(18)、式(21)、式(22)带入式(23)，可以得到沿

三个方向单位磁偶极子产生的电场和磁场各分量的解析式及Sommerfeld积分形式，其中电场和磁场z分量的Sommerfeld积分形式分别用如下表达式表示：in,

represents the conductivity tensor of a homogeneous anisotropic medium, and H represents the Hertz potential. Substituting formula (18), formula (21), and formula (22) into formula (23), we can get along

Analytical expressions and Sommerfeld integral forms of the electric and magnetic field components generated by unit magnetic dipoles in three directions, in which the Sommerfeld integral forms of the z-components of the electric field and magnetic field are expressed by the following expressions:

E _z ⁽³⁾ (r, r _t )=0 (26)

三个方向单位磁偶极子在z方向上电场分量，H_z ⁽¹⁾、H_z ⁽²⁾、H_z ⁽³⁾分别表示沿

三个方向单位磁偶极子在z方向上磁场分量，上述各分量均被表示成了波模积分的形式。例如：Among them, E _z ⁽¹⁾ , E _z ⁽²⁾ , and E _z ⁽³⁾ represent edge

The electric field components of the unit magnetic dipole in the three directions in the z direction, _Hz ⁽¹⁾ , _Hz ⁽²⁾ , _Hz ⁽³⁾ represent the direction along the

The magnetic field components of the unit magnetic dipoles in the three directions in the z-direction are expressed in the form of wave mode integrals. E.g:

表示某一积分变量λ对应的波模，λ表示积分变量。in,

represents the wave mode corresponding to an integral variable λ, and λ represents the integral variable.

According to Maxwell's equations, the relationship between the tangential and longitudinal components of the electric and magnetic modes can be expressed by the following expressions:

分别表示磁场在x、y、z方向上的分量，

分别表示电场在x、y、z方向上的分量，ε_h表示水平介电常数、μ表示磁导率，将式(24)～式(29)中对应的变量代入式(30)～式(31)即可分别计算得到电场和磁场x、y分量。而后，根据接收线圈处的电场强度或磁场强度计算得到接收线圈处的感应电动势，进而计算得到两个接收线圈之间的相位差和幅度比值，再经过电阻率转换即可得到相位差电阻率与幅度比电阻率，从而形成了地层模型-电磁波电阻率曲线数值-仪器类型关系库。进一步根据边界距指示极化值与对应的边界距的关系，按照上述分类顺序结果进行保存，便可得到地层模型-电磁波电阻率曲线-边界距的关系库，以完成地质模型快速反演数据库的构建。in,

represent the components of the magnetic field in the x, y, and z directions, respectively,

respectively represent the components of the electric field in the x, y, and z directions, ε _h represents the horizontal permittivity, and μ represents the magnetic permeability. Substitute the corresponding variables in equations (24) to (29) into equations (30) to ( 31) The x and y components of the electric field and the magnetic field can be calculated separately. Then, the induced electromotive force at the receiving coil is calculated according to the electric field strength or magnetic field strength at the receiving coil, and then the phase difference and amplitude ratio between the two receiving coils are calculated, and then the phase difference resistivity and Amplitude specific resistivity, thus forming formation model-electromagnetic wave resistivity curve numerical-instrument type relation library. Further, according to the relationship between the polarization value and the corresponding boundary distance indicated by the boundary distance, and the results of the above classification sequence are stored, the relationship library of stratigraphic model-electromagnetic wave resistivity curve-boundary distance can be obtained to complete the rapid inversion database of geological model. Construct.

Among them, the geological model inversion database is equipped to simulate the boundary distance parameters and the relative dip angle of the wellbore formation under different environments such as different measuring instruments and different formation resistivities. During the inversion process, it is necessary to obtain the corresponding real operation while drilling. The corresponding electromagnetic wave resistivity curve can be obtained according to the formation characteristic parameters of the environment and the instrument parameters, so as to obtain the real formation parameters including the relative dip angle of the wellbore formation, the distance from the measurement point to the formation boundary and the layer thickness, etc. The fast inversion process solves the problems of large amount of calculation and slow calculation speed in the steerable while drilling operation, and achieves the purpose of high speed and high efficiency.

Specifically, taking the initial formation model while drilling as the initial value, the gradient descent method is used to construct the objective function, the logging response results of the initial formation while drilling model are compared with the measured data, and the residual between the logging response and the measured data is calculated to determine According to the descending direction and the corresponding descending step length, the model correction amount corresponding to the preliminary corrected initial stratum model while drilling can be calculated, that is, the preliminary corrected initial stratum while drilling model.

Based on the above-mentioned geological model inversion database, the value of the logging response of the initial corrected formation while drilling model was found by the quick database search method, and the values of the initial corrected initial formation while drilling model were compared (logging response) and real-time measurement data to obtain a new initial model (initial stratum-while-drilling model after secondary correction), and further use the construction result of the new initial model (initial stratum-while-drilling model after secondary correction) as this The second inversion results are used to obtain the deep real formation data, which is used as the data basis for deep formation steering operations.

Specifically, the quick database search method includes the following steps: First, according to the initial value model parameter values of the initial model of the formation while drilling, search is performed according to the index order of the forward modeling simulation library, and the logging response corresponding to the corrected initial model is obtained. ; Second, according to the comparison between the logging response and the logging response of the measured data, the following least squares objective function is established; the Jacobian matrix of the objective function is solved by the gradient descent method, and the Jacobian linear equation system is formed, and the objective function is the fastest by solving the equation system. Descending direction; third, solve the objective function, determine the step size in the direction of the fastest descent, and further change the direction and step size according to the obtained fast inversion initial model, determine the change amount of the model, change the model, and complete a model update; By setting the loop termination condition, the model update process is called cyclically until the loop termination condition is met, so as to construct a new initial model, complete the fast database search and inversion processing, and obtain the corresponding real formation parameters, and go to step S150. Among them, the real parameters of the formation include at least formation horizon division data, formation resistivity, formation natural gamma, etc. The formation horizon division data includes: formation resistivity value, distance from (instrument) measurement point to layer boundary, and formation layer thickness, etc. .

In step S150, according to the real stratum parameters obtained by the quick library search method, including the relative dip angle of the wellbore stratum, the stratum resistivity value, the position of the stratum layer interface and the change of the layer thickness in the horizontal displacement direction, the stratum is not encountered in the stratum. Interface position prediction, further carry out equal dip extension of the undrilled strata, predict the change of the layer interface along the well axis of the horizontal well to be drilled, and calculate the safety distance of the drill bit in the target layer to guide the geosteering operation, especially It is the adjustment of the drill bit.

The specific implementation process of drill bit adjustment includes the following steps:

First (step S1501), according to the relative inclination of the wellbore formation in the real formation parameters obtained by inversion, and the measured value of the inclination angle of the drill bit obtained in real time, calculate the apparent inclination of the formation, determine the direction of the drill bit, and use the following expression to calculate:

γ=φ-α (34)

Among them: γ represents the apparent dip angle of the formation, φ represents the relative dip angle of the wellbore formation obtained after inversion, and α represents the well inclination angle. It should be noted that when γ>0, the stratum is a downdip stratum; when γ<0, the stratum is an updip stratum. When the formation is up-dipping, in order to ensure that the drill bit travels through the proper position of the formation, the rotor needs to be adjusted upward. Similarly, when the formation is down-dipping, the drill bit should be adjusted downward to ensure that the bit does not come out from the top of the formation. Among them, the optimal adjustment angle It needs to be determined according to the γ value.

Second (step S1502 ), according to the apparent dip angle of the formation and the inversion real formation parameters including formation resistivity value, formation true dip angle γ, and formation thickness H, follow the formation to predict formation resistivity Rt, upper and lower formation resistivity outside the detection range (RT ₁ , RT ₂ ) and the variation of the formation thickness in the horizontal direction (well axis direction), draw a two-dimensional cross-sectional view of the formation.

Third (step S1503), according to the two-dimensional cross-sectional view of the stratum, the distance between the drill bit and the measurement point and the direction of the drill bit, predict the position of the layer interface with an iso-inclined extension on the stratum that has not been drilled, and further calculate the distance that the drill bit drills out of the target layer .

6a is a schematic diagram of the location of the bit and the distance between the bit and the formation interface in geosteering when the inclination angle of the bit is less than 90° in the method for predicting bit adjustment for geosteering according to an embodiment of the present invention. As shown in Figure 6a, in this case, it is necessary to use the relative dip angle of the wellbore formation in the real formation parameters and the distance from the measurement point to the formation boundary to calculate the distance between the drill bit and the upper boundary of the formation, so as to obtain the distance between the drill bit and the lower boundary of the formation, which is used to determine The position of the drill bit in the target layer, and then, according to the distance between the drill bit and the lower interface of the formation, predict the distance that the drill bit drills out of the lower interface of the formation, and use it as the safety distance for the drill bit to adjust.

First, using the relative dip angle of the wellbore formation, the distance between the tool measurement point and the formation boundary (here is the upper boundary), and the distance between the tool measurement point and the bit, the following expressions can be used to calculate the distance between the bit and the upper boundary of the formation, and the distance between the bit and the lower boundary of the formation Distance (as shown in Figure 6a):

DTB _Bit-u = DTB+L*sinφ (35)

Among them, DTB _Bit-u represents the distance between the drill bit and the upper boundary of the formation, DTB represents the distance from the measurement point to the formation boundary, L represents the distance between the drill bit and the measurement point of the tool, and φ represents the relative dip angle of the wellbore formation.

Further, the following expression is used to express the distance between the drill bit and the lower interface of the formation:

DTB _Bit-d = H-DTB _Bit-u (36)

Among them, DTB _Bit-d represents the distance between the drill bit and the lower interface of the formation, and H represents the thickness of the formation in the real formation parameters. When DTB _Bit-d > 0, it means that the drill bit is still in the target layer, and when DTB _Bit-d is less than 0, it means that the drill bit has drilled into the lower formation.

Finally, according to the obtained distance between the bit and the lower interface and the relative dip angle of the wellbore formation, the following expression can be used to predict the distance that the bit drills out of the lower interface of the formation:

S=DTB _Bit-d *tanφ(37)

In the formula, S represents the distance that the drill bit drills out of the lower boundary of the formation. At this time, the drilling engineer should give advance warning based on the relative dip angle of the wellbore formation and the distance the drill bit drills out of the lower boundary of the formation, and conduct risk assessment based on the drilling parameters to ensure that the drill bit does not drill out of the target layer.

6b is a schematic diagram of the location of the bit and the distance between the bit and the formation interface in geosteering when the inclination angle of the bit is greater than 90° in the method for predicting bit adjustment for geosteering according to an embodiment of the present invention. As shown in Figure 6b, in this case, it is necessary to use the relative dip angle of the wellbore formation in the real formation parameters and the distance from the measurement point to the formation boundary to calculate the distance between the bit and the lower boundary of the formation, so as to obtain the distance between the bit and the upper boundary of the formation, which is used to determine The position of the drill bit within the target layer. Then, according to the distance between the drill bit and the upper interface of the formation, predict the distance that the bit drills out of the upper interface of the formation, and use it as the safety distance for the adjustment of the drill bit.

First, using the relative dip angle of the wellbore formation, the distance between the tool measurement point and the formation interface (here is the lower boundary), and the distance between the tool measurement point and the drill bit, the following expressions can be used to calculate the distance between the drill bit and the lower interface DTB _Bit-d and the distance from the upper interface DTB _Bit-u (as shown in Figure 6a):

DTB _Bit-d = DTB+L*sinφ (38)

Among them, DTB _Bit-d represents the distance between the drill bit and the lower boundary of the formation, DTB represents the distance from the measurement point to the formation boundary, L represents the distance between the drill bit and the measurement point of the tool, and φ represents the relative dip angle of the wellbore formation.

Further, the following expression is used to express the distance between the drill bit and the upper interface of the formation:

DTB _Bit-u = H-DTB _Bit-d (39)

Among them, DTB _Bit-u represents the distance between the drill bit and the upper interface of the formation, and H represents the thickness of the formation in the real formation parameters. When DTB _Bit-u >0, it means that the drill bit is still in the target layer, and when DTB _Bit-u is less than 0, it means that the drill bit has drilled into the lower formation.

Finally, according to the distance between the bit and the upper interface obtained above and the relative dip angle of the wellbore formation, the following expression can be used to predict the distance that the bit drills out of the upper boundary of the formation:

S=DTB _Bit-u *tanφ (40)

In the formula, S represents the distance that the drill bit drills out of the upper boundary of the formation. At this time, the drilling engineer should give early warning based on the relative dip angle of the wellbore formation and the distance the drill bit drills out of the upper boundary of the formation, etc., and conduct risk assessment according to the drilling parameters to ensure that the drill bit does not drill out of the target layer.

7 is a geosteering real-time inversion cross-sectional view (a two-dimensional cross-sectional view of the formation) of the drill bit adjustment prediction method for geosteering according to an embodiment of the present invention. As shown in Figure 7, the first track from bottom to top is the two-dimensional profile track of the geological model; the second track is the depth track of the measurement point; the third track is the phase difference resistivity track; the fourth track is the amplitude specific resistivity track The fifth track is the formation boundary indicator signal track; the sixth track is the azimuth gamma imaging track.

The invention combines the azimuth-while-drilling gamma imaging logging data and the electromagnetic wave resistivity logging data while drilling to perform geosteering, and firstly obtains initial formation logging parameters and/or logging parameters by inverting the data of offset wells and/or pilot wells. Second, use the azimuth gamma imaging data to calculate the formation dip, and use the electromagnetic wave resistivity curve while drilling to extract the boundary distance indicator signal to calculate the formation boundary distance, and update the initial formation model in real time. On the updated stratigraphic model, a fast inversion library is established by using the analytical numerical simulation algorithm, and the measured data is quickly inverted with the gradient descent method to obtain parameters such as the real resistivity, relative dip angle, and boundary distance of the formation. Further, through the wellbore trajectory data, the apparent dip angle of the formation is calculated, the distance between the bit and the boundary is predicted, and the safety distance for bit adjustment is calculated to guide the adjustment of the geosteering bit. The invention can obtain the formation dip, the position of the layer interface and the relative relationship between the instrument and the layer interface from the measured data, and then can calculate the safety distance of the drill bit adjustment in the geosteering, which is a data processing technology urgently needed in production. The detection advantages of various logging data, complementary advantages, comprehensive utilization, improve the efficiency of logging data utilization, and can mine more and richer formation information from existing data without adding logging projects.

The above is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Any person familiar with the technology can easily think of changes or substitutions within the technical scope disclosed by the present invention. , all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (10)

1. A method of predicting bit adjustment for geosteering, the method comprising the steps of:

firstly, carrying out rapid inversion processing on standardized logging data of adjacent wells and/or pilot holes, dividing stratum positions according to inversion results, and constructing a geosteering model;

obtaining corresponding measurement while drilling parameters including a relative inclination angle of a borehole stratum, a stratum azimuth angle and a boundary distance indication polarization value by using actual measurement data of a while-drilling azimuth gamma imaging logging curve and a while-drilling electromagnetic wave resistivity logging curve which are obtained in real time in the operation of the well logging while drilling;

step three, correcting the geosteering model in real time by combining the measurement while drilling parameters, and establishing a formation initial model while drilling;

fourthly, based on a response result of the formation initial model while drilling, inverting a database according to a preset geological model, and further correcting the formation initial model while drilling through a rapid library search method to obtain formation real parameters, wherein the formation real parameters comprise the relative inclination angle of the well stratum, the distance from a measuring point to a stratum boundary and the thickness of the stratum;

and fifthly, according to the real stratum parameters, carrying out equal inclination angle sequential extension on the stratum not drilled and encountered, and predicting the change of the layer interface in the well shaft direction of the horizontal well to be drilled and the safe distance adjusted by the drill bit so as to guide the geosteering operation.

2. The method of claim 1, wherein step five further comprises:

acquiring a well inclination angle of a drill bit, and calculating a formation apparent inclination angle;

predicting the change of the formation resistivity and the formation layer thickness outside the detection range along the well axis direction according to the formation dip angle and the formation real parameters, and drawing a two-dimensional profile of the formation;

and predicting the layer interface position of the stratum which is not met by drilling according to the stratum two-dimensional profile, the distance between the drill bit and the measuring point and the direction of the drill bit, and further determining the distance of the drill bit for drilling the target layer.

3. The method of claim 1 or 2, wherein the fourth step further comprises:

comparing the response result of the formation initial model while drilling with the measured data, and obtaining a model correction amount corresponding to the formation initial model while drilling after primary correction by using a gradient descent method;

and searching the logging response of the initially corrected formation initial model while drilling from the geological model inversion database by using the model correction amount, comparing the logging response obtained by searching the database with the measured data to obtain a formation initial model while drilling after secondary correction, and further taking the formation initial model while drilling after secondary correction as an inversion result to obtain the corresponding formation real parameter.

4. The method according to claim 1 or 2, characterized in that in step four,

establishing a classified forward geological simulation model library according to stratum characteristic parameters of an area where a horizontal well to be drilled is located in logging-while-drilling operation and measurement-while-drilling instrument parameters;

and performing numerical forward simulation calculation on each category parameter in the classified forward geological simulation model library by using an analytic solution numerical simulation algorithm based on Maxwell equation to obtain a relation of a stratum model-an electromagnetic wave resistivity curve-a boundary distance, and forming the geological model inversion database.

5. The method of claim 1, wherein step one further comprises the steps of:

acquiring stratum resistivity and stratum structure parameters obtained after rapid inversion processing, performing stratum layer division on an inversion result by using an inflection point method, determining a stratum layer interface and displaying a layer division result of a corresponding relation between the horizontal direction and the depth of the stratum layer;

and taking the well logging data of the adjacent well and/or pilot hole well after the standardized preprocessing as initial parameters, and combining the layer division result to obtain the geosteering model.

6. The method according to claim 5, wherein in the step of using an inflection point method to perform stratum horizon division on the inversion result, determining a stratum interface and displaying a horizon division result showing a corresponding relationship between a horizontal direction and a depth of the stratum horizon, the method further comprises:

if a plurality of adjacent wells are provided, each adjacent well needs to be layered, and stratum layer division conditions corresponding to the well position coordinates of the horizontal well to be drilled and each adjacent well are obtained;

and comparing and linking the layering results of the adjacent well layers according to the adjacent well position coordinate distribution information to obtain the layer division result showing the corresponding relation between the horizontal direction and the depth of the whole stratum layer of the horizontal well to be drilled.

7. The method according to claim 1 or 2, wherein in the second step, the relative inclination of the borehole formation is obtained by:

determining the depth of the azimuth gamma imaging data crossing layer interface position according to the orientation gamma imaging logging while drilling curve acquired in real time by using an inflection point method;

calculating the elevation difference of the azimuth gamma imaging data according to the depth of the azimuth gamma imaging data penetrating through the interface position of the layer;

and extracting the relative inclination angle of the well stratum from the orientation gamma imaging logging while drilling curve according to the elevation difference of the orientation gamma imaging data based on the acquired current pilot well diameter curve and the detection depth of the orientation gamma imaging instrument.

8. The method of claim 5 or 6, wherein the step three further comprises:

determining the number of stratum layers, the resistivity of each layer and the change of the layer thickness in the transverse direction according to the response data of the geosteering model and the layer position division result;

correcting the relative inclination angle of the well stratum obtained in the geosteering model by using the relative inclination angle of the well stratum extracted from the orientation gamma imaging logging while drilling curve;

and calculating the distance between the measuring point and the formation boundary surface according to the boundary distance indication polarization value obtained by the logging curve of the electromagnetic wave resistivity while drilling, further performing depth correction on the corresponding relation between the horizontal direction and the depth of the formation horizon in the geosteering model after the correction of the relative inclination angle of the borehole and the formation, and establishing the initial model of the formation while drilling.

9. The method as claimed in claim 2, wherein in the step of further determining the distance that the drill bit drills the target formation based on the two-dimensional profile of the formation, the distance from the drill bit to the measurement point, and the drill bit direction, for the prediction of the location of the layer interface with equal inclination angle for the formation not drilled, when the drill bit angle is less than 90 degrees, further comprising:

calculating the distance between the drill bit and the upper interface of the stratum by using the stratum real parameters including the relative inclination angle of the borehole stratum and the distance between the measuring point and the stratum boundary, thereby obtaining the distance between the drill bit and the lower interface of the stratum and determining the position of the drill bit in the target layer;

and predicting the distance of the drill bit for drilling the underground interface of the stratum according to the distance between the drill bit and the underground interface of the stratum, and taking the distance as the safety distance for adjusting the drill bit.

10. The method as claimed in claim 2 or 9, wherein in the step of further determining the distance that the drill bit drills the target formation based on the two-dimensional profile of the formation, the distance from the drill bit to the measurement point and the direction of the drill bit, for the prediction of the location of the layer interface with equal inclination angle for the formation not yet drilled, when the drill bit inclination angle is greater than 90 degrees, further comprising:

calculating the lower interface distance between the drill bit and the stratum by utilizing the stratum real parameters comprising the relative inclination angle of the borehole stratum and the distance from the measuring point to the stratum boundary, thereby obtaining the upper interface distance between the drill bit and the stratum and determining the position of the drill bit in the target layer;

and predicting the distance of the drill bit for drilling the interface on the stratum according to the distance between the drill bit and the interface on the stratum, and taking the distance as the safety distance for adjusting the drill bit.

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