CN101403301B - A Method for Acquiring Regional Distribution Law of Reservoir Granularity - Google Patents

Abstract

The invention discloses a method for obtaining a distribution rule of a reservoir granularity area, which comprises the following steps: performing oil field geological exploration on the prediction block, and acquiring a fast deposition migration rule of the block according to a geological exploration result; dividing the prediction block into different blocks according to the sedimentary microfacies unit bodies divided in the geological exploration result; correcting the divided blocks according to the actual measurement data of the core granularity of the exploratory well on the prediction blocks; and obtaining the transverse granularity distribution rule of the prediction block by utilizing an interpolation method. The invention solves the defect of insufficient coring data of a block development well and performs the prediction of the distribution rule from point to surface. The design of the well completion sand prevention scheme is carried out according to the predicted longitudinal and transverse distribution rule of the granularity, the design result is more accurate and reliable, and the method has important significance for improving the development efficiency of the oil field and the productivity of the oil well.

Description

A Method for Acquiring Regional Distribution Law of Reservoir Granularity

technical field

The invention relates to the technical field of geological exploration, in particular to a new grain size prediction method, which is a method for predicting the grain size distribution law of a reservoir area by combining actual measurement with sedimentary microfacies.

Background technique

At present, before the comprehensive development of a new block that may produce sand, more and more attention has been paid to designing a reasonable completion and sand control scheme. Scholars at home and abroad have conducted a lot of in-depth research on this, and proposed different completion methods for different reservoir characteristics. Well sand control program design methods, these methods are based on known reservoir particle size distribution, therefore, it has become more and more important to accurately predict the vertical and horizontal regional distribution of oilfield reservoir particle size.

At present, the data of reservoir particle size basically come from the particle size test data of cores. The cores or cuttings obtained from coring wells are tested by laser particle size analyzer or sieve analyzer, and then the tested data are used as the sand control plan design for development well completion. The data obtained in this way are accurate and direct. Although the data obtained through core particle size testing is more accurate and direct, due to the small number of exploratory wells in a new block and limited coring, it is not enough to clarify the vertical and horizontal particle size distribution of the entire area; in addition, the core test results of exploratory wells are not It can fully reflect the reservoir granularity characteristics of the development well.

Contents of the invention

The purpose of the present invention is to finally obtain the vertical and horizontal distribution of grain sizes of different reservoirs in the area based on the results of the actual measurement of the grain size of the stratum core, combined with the migration law of the sedimentary microfacies in the whole area and the geological and lithological logging data, and using the mathematical interpolation function. The optimal design of well sand control scheme provides reliable basic data support.

In order to achieve the above object, the technical solution of the present invention provides a method for obtaining the regional distribution of reservoir granularity, including the following steps:

S101, carry out oilfield geological exploration on the predicted block, and obtain the sedimentary migration law of the block according to the geological exploration results;

S102. Dividing the predicted block into different blocks according to the sedimentary microfacies units divided in the geological exploration results;

S103, correcting the divided blocks according to the measured data of the core particle size of the exploratory well on the predicted block;

S104, using an interpolation method to obtain the horizontal granularity distribution law of the predicted block;

Wherein, the interpolation method includes the following steps: establish a plane reference coordinate system according to the well position geodetic coordinates of each well, and provide the three-dimensional coordinate values of the sample points; determine the boundaries of each well area according to the changing orientation of the sedimentary microfacies , carry out segmentation on the changing azimuth trend line, and then combine the particle size change range of different sedimentary microfacies to give the extreme value of particle size change in each segment; set the initial particle size change factor, including the change factor in X direction and Y direction; perform plane interpolation , to judge whether the interpolation result of each point on the plane satisfies the particle size range of the sedimentary microfacies, if not, change the change factor, and cycle the interpolation calculation until the interpolation result reaches the set calculation accuracy and then end the cycle; obtain the equivalent value of the entire area line graph.

Wherein, the sedimentary migration rule is that the predicted block is littoral or fluvial sediments.

Wherein, the sedimentary microfacies unit includes: underwater distributary channel, underwater distributary bay, mouth bar, far sand bar, underwater natural embankment, front sheet sand or prodelta mud.

Wherein, the lithology of the underwater distributary channel is medium-fine-grained sandstone, pebble-containing sandstone and glutenite, and the median particle size range is above 500um.

Wherein, the lithology of the underwater distributary bay is silt-fine sandstone and a small amount of pebble-bearing sandstone, and the median particle size ranges from 250-500um.

Wherein, the lithology of the mouth bar and the far sand bar is fine sandstone, and the median particle size range is 125-250um.

Wherein, the lithology of the underwater natural dike and front sheet sand is fine silt and fine sandstone, and the median particle size range is 50-125um.

Wherein, the lithology of the prodelta mud is mudstone, and the median particle size range is below 50um.

The above-mentioned technical scheme has the following advantages:

1. Solved the shortcoming of insufficient coring data for development wells in a block, and realized the distribution law prediction from point to surface.

2. It can intuitively reflect the particle size distribution characteristics of the reservoir section of the development well at any position in the block, and solve the problem that the core test results at the exploration well position cannot fully reflect the particle size characteristics of the development well reservoir.

3. According to the predicted vertical and horizontal distribution of particle size, the completion sand control scheme design is more accurate and reliable, which is of great significance for improving the development efficiency of oilfields and increasing the productivity of oil wells.

Description of drawings

Fig. 1 is a flow chart of a method for obtaining regional distribution of reservoir granularity according to an embodiment of the present invention;

Fig. 2 is the distribution diagram of production wells and water injection wells in Weizhou 11-1N oil field of the embodiment of the present invention;

Fig. 3 is a contour map of the regular grain size distribution area of Weizhou 11-1N oil field according to the embodiment of the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

As shown in Figure 1, firstly, according to the geological exploration test results in the early stage of the oilfield, the sedimentary migration law of the block is summarized, including whether the block is littoral or fluvial deposition and its deposition direction. Microfacies units (subaqueous distributary channel, underwater distributary bay, mouth bar, far sand bar, underwater natural dike, front sheet sand, prodelta mud, etc.), divide the entire region into sedimentary bodies with different characteristics ; For different sedimentary systems, sedimentary microfacies have obvious directionality, and usually gradually transition from provenance to delta front, so this trend is conducive to the division of sedimentary systems according to sedimentary microfacies, determine the boundary conditions, and then use The measured data of the core grain size of the exploratory wells in this block is corrected, so that the contour map of the lateral grain size distribution of the whole area can be made by using mathematical methods.

According to a large number of core particle size test data, combined with mud logging lithology interpretation and sedimentary microfacies division, the approximate particle size distribution range of different sedimentary microfacies and the corresponding relationship between lithology can be calculated, as shown in the following table:

Sedimentary microfacies Lithology Median particle size range underwater distributary channel Medium-fine-grained sandstone, pebble-bearing sandstone and glutenite Above 500um Underwater Distributary Bay Silt-fine sandstone and a small amount of pebble-bearing sandstone 250-500um Mouth bar, far sand bar Fine sandstone 125-250um Underwater natural embankment, front sheet sand Fine silt, fine sandstone 50-125um Front Delta Mud Mudstone Below 50um

After clarifying the basic laws of sedimentary microfacies and grain size distribution, the grain size of the area can be further refined by using the data interpolation method, and the contour map of the grain size distribution of the entire area can be made.

The interpolation algorithm is to construct a function with known data points to estimate its function value at the unknown point without knowing the exact function. The stability and smoothness of the piecewise spline interpolation algorithm make it an effective algorithm for interpolating between known points. Due to the limited number of sample points on the planar area, only these measured sample points are used for interpolation, and the reliability of the interpolation results on the peripheral area of the sample points is low. Therefore, the key lies in the setting of boundary conditions. Accurately set boundary conditions according to the change trend of sedimentary microfacies. With the help of numerical calculation software, the optimal contour map of the grain size distribution area can be finally obtained, and it can well meet the variation law of sedimentary microfacies and the measured data of grain size. Meet the requirements of engineering applications.

The specific implementation steps are as follows:

First, a plane reference coordinate system is established according to the geodetic coordinates of each well location, and the function values (Xi, Yi, Zi) of the sample points are given;

According to the change orientation of sedimentary microfacies, the approximate boundary of each well area is determined, segmented on the change orientation trend line, and then combined with the grain size change range of different sedimentary microfacies, the extreme value of grain size change in each segment is given;

Set a reasonable initial particle size change factor, including the change factors in the X direction and the Y direction. The change factor can be set at will, but if the setting is not appropriate, it may affect the accuracy if it is too large, and the program will run excessively if it is too small; therefore, it is necessary to combine The grain size of the core is determined by the measured data. Usually, the minimum difference in the median grain size when the sedimentary microfacies changes from one state to another is set as the initial change factor.

Use numerical calculation software to perform plane interpolation, and judge whether the interpolation result of each point on the plane satisfies the particle size range of sedimentary microfacies (assuming that the interpolation result reaches the set calculation accuracy, it is satisfied), if not, change the change factor and cycle interpolation The calculation program will end the loop until the interpolation result reaches the set calculation accuracy.

Output the optimized contour map of the entire area.

On the basis of clarifying the particle size distribution in the whole area, the completion sand control scheme design for the development well will be more accurate and reliable, which is of great significance for improving the development efficiency of the oil field and the productivity of the oil well.

The following takes Weizhou 11-1N Oilfield as an example to describe in detail:

The Paleogene in the Weixinan Sag where the Weizhou 11-1N Oilfield is located has experienced a whole process of development, decline, and extinction of inland lacustrine deposits from the beginning of the Changliu Formation to the end of the Weizhou Formation. The reservoirs of Weizhou 11-1N oilfield are mainly concentrated in the first member of Liu, which is mainly fan delta-shallow lake facies, interbedded deposits of sandstone and mudstone with different thickness, the formation thickness is 350m-450m, and the distribution is relatively stable.

The first member of Liuliu can be divided into three parts: upper, middle and lower. The stratigraphic characteristics of the oilfield are significantly different. The upper strata is about 100m-170m thick, and it is a coastal shallow lacustrine deposit. The strata in the middle are about 170m-270m thick and are deposited at the front of the fan delta. The sandstone is relatively developed, and the oil layers of this oilfield are mainly distributed in it. Among them, the lower part is interbedded with gray powder, fine sandstone and mudstone, the middle part is oil-rich, oil-soaked and oil-spotted sandstone, light brown-gray oil-soaked coarse sandstone, glutenite interbedded with gray mudstone; the upper part is gray siltstone interbedded with mudstone . It has a fine-coarse-fine cycle characteristic from bottom to top. The lower stratum is about 60m-100m thick, mainly composed of middle-deep lacustrine deposits.

In this embodiment, taking the upper oil formation II, the main reservoir in the middle part of the first member of Liuyu Formation as an example, the grain size lateral distribution law of the entire oil formation is predicted based on the sedimentary microfacies, mud logging lithology and the core grain size measurement data of three exploratory wells in this block.

1. Distribution of sedimentary microfacies in L1II upper oil formation of WZ11-1N oilfield

L1II Shangyou Formation is the heyday of the development of steep slope fan delta deposition in the northwest uplift provenance, and the sand bodies are widely distributed, and all four exploration wells drilled this layer. Along the flow direction, from north-west to south-east, the underwater distributary channel deposits gradually become front sheet sand, and the regional distribution pattern is very obvious.

According to mud logging data, the lithology changes also show regular changes: medium-coarse sandstone interbedded with pebble-bearing sandstone-medium-fine-grained sandstone interbedded with a small amount of pebble-bearing sandstone-fine sandstone-fine siltstone. Therefore, according to the changes in sedimentary microfacies and lithology, it can be judged that the general trend of the grain size distribution of the reservoir gradually decreases from the northwest provenance to the southeast delta front.

2. Statistics of the measured particle size data of L1II upper oil formation in WZ11-1N oilfield

A total of four exploration wells were drilled in this block, three of which were cored. After screening the cored rock samples, more than 60 samples from the L1II upper oil formation were selected at equal intervals according to the sampling well depth for laser particle size measurement.

According to the particle size test results, the approximate range of the particle size distribution of the three wells can be calculated as shown in the table below. The change trend gradually decreases from Well 2 to Well 4 to Well 3, which is basically consistent with the change orientation of sedimentary microfacies.

hashtag Median particle size D50(um) Well WZ11-1N-2 500-1000 Well WZ11-1N-4 200-500 Well WZ11-1N-3 100-200

According to the variation trend of sedimentary microfacies and measured grain size, the L1II upper oil formation of this oilfield can be divided into three well areas: well area 2, well area 4 and well area 1-3. It can be seen at a glance from Figure 2 that there are 7 production wells (A1, A2, A3, A4, A5, A6, A7H) and 6 water injection wells (A8, A9, A10, A11, A12, A13) in WZ11-1N Oilfield It is basically located in which well area, which is conducive to the design of the completion sand control plan for each well. According to the division of the well area, the particle size measurement data of the corresponding coring well can be referred to, so as to grasp the design parameters as accurately as possible, optimize the Design. Among them, the direction of the arrow in Figure 2 refers to the direction in which the median grain size of pebble-bearing coarse sandstone is from above 500um to about 100um.

3. Contour map of lateral grain size distribution of L1II upper oil group in WZ11-1N oilfield

After clarifying the basic laws of sedimentary microfacies and grain size distribution, the grain size of the area can be further refined by using the data interpolation method, and the contour map of the grain size distribution of the entire area can be made.

The interpolation algorithm is to construct a function with known data points to estimate its function value at the unknown point without knowing the exact function. The stability and smoothness of the piecewise spline interpolation algorithm make it an effective algorithm for interpolating between known points. Due to the limited number of sample points on the planar area, only these measured sample points are used for interpolation, and the reliability of the interpolation results on the peripheral area of the sample points is low. Therefore, the key lies in the setting of boundary conditions. How to accurately set the boundary conditions will use the changing trend of sedimentary microfacies. With the help of numerical calculation software, the optimal contour map of the grain size distribution area can be finally obtained, and it can well meet the variation law of sedimentary microfacies and the measured data of grain size. Meet the requirements of engineering applications. As shown in Fig. 3, the areas of Wells 1 and 3 are fine sandstone and silty sandstone, the area of Well 2 is medium-coarse pebble-bearing sandstone, and the area of Well 4 is medium-fine pebble-bearing sandstone.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (8)

1. a method of obtaining container layer coarseness area distribution rule is characterized in that, may further comprise the steps:

S101 carries out the oil field geologic exploration to prediction block, obtains the deposition migration rule of this block according to the geological prospecting result;

S102 according to the deposition microphase unit bodies of dividing among the geological prospecting result, is divided into different blocks with said prediction block;

S103 proofreaies and correct the block of dividing according to the rock core granularity measured data of prospect pit on the said prediction block;

S104 utilizes the method for interpolation to obtain the horizontal particle size distribution law of said prediction block;

The method of said interpolation may further comprise the steps:

Well location geodetic coordinates according to every mouthful of well is set up the plane reference frame, and provides the D coordinates value of sample point;

Make the border of each wellblock according to the variation orientation of sedimentary micro, carry out segmentation changing on the directional tendency line, combine the change of granularity scope of different sedimentary micro to provide every section change of granularity extreme value again;

The initial particle size changed factor is set, comprises the changed factor of directions X and Y direction;

Carry out planar interpolation, judge whether the interpolation result of each point on the plane satisfies the particle size range of sedimentary micro, as not satisfying, change changed factor, the circulation interpolation calculation reaches end loop after the computational accuracy of setting up to interpolation result;

Obtain the isogram in whole zone.

2. the method for obtaining container layer coarseness area distribution rule as claimed in claim 1 is characterized in that, said deposition migration rule is that said prediction block is littoral facies deposition or river facies deposition.

3. the method for obtaining container layer coarseness area distribution rule as claimed in claim 1; It is characterized in that said deposition microphase unit bodies comprises: distributary channel, gulf, estuary dam between shunting, sand dam far away, natural levee, leading edge sheet sand or prodelta mud under water under water under water.

4. the method for obtaining container layer coarseness area distribution rule as claimed in claim 3 is characterized in that, the lithology of said distributary channel under water is middle fine sandstone, pebbly sandstone and glutenite, and the median grain diameter scope is more than the 500um.

5. the method for obtaining container layer coarseness area distribution rule as claimed in claim 3 is characterized in that, said under water between shunting the lithology in gulf be powder packsand and a small amount of pebbly sandstone, the median grain diameter scope is 250-500um.

6. the method for obtaining container layer coarseness area distribution rule as claimed in claim 3 is characterized in that, the lithology on said estuary dam, sand dam far away is a packsand, and the median grain diameter scope is 125-250um.

7. the method for obtaining container layer coarseness area distribution rule as claimed in claim 3 is characterized in that, the lithology of said natural levee under water, leading edge sheet sand is fine silt, packsand, and the median grain diameter scope is 50-125um.

8. the method for obtaining container layer coarseness area distribution rule as claimed in claim 3 is characterized in that, the lithology of said prodelta mud is a mud stone, and the median grain diameter scope is below the 50um.

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