CN118348045B - Analysis method of fluid occurrence state in rock 2D nuclear magnetic T1-T2 weighted centroid - Google Patents
Analysis method of fluid occurrence state in rock 2D nuclear magnetic T1-T2 weighted centroid Download PDFInfo
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- 239000012530 fluid Substances 0.000 title claims abstract description 109
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Abstract
本发明提供了一种岩石二维核磁T1‑T2加权质心流体赋存状态分析方法,其是先获取含水岩石的二维核磁T1‑T2分布数据，利用提出的加权质心计算方法将核磁谱图原始数据进行转化，以得到质心坐标并计算各质心所对应的T1/T2值，以分析储层岩石内流体赋存和动态运移规律。本发明克服了现有二维核磁共振数据处理方法难以对多组数据进行对比分析的缺陷，简化了二维核磁共振分布数据的展现方式，并为二维核磁共振数据的定量化分析提供了新的参考标准，解决了现有二维核磁共振数据处理方法难以对多组数据进行对比分析的缺陷。
The present invention provides a rock two-dimensional nuclear magnetic resonance T 1 ‑T 2 weighted centroid fluid occurrence state analysis method, which first obtains the two-dimensional nuclear magnetic resonance T 1 ‑T 2 distribution data of water-bearing rocks, and transforms the original data of the nuclear magnetic spectrum using the proposed weighted centroid calculation method to obtain the centroid coordinates and calculate the T 1 /T 2 values corresponding to each centroid, so as to analyze the fluid occurrence and dynamic migration law in the reservoir rock. The present invention overcomes the defect that the existing two-dimensional nuclear magnetic resonance data processing method is difficult to compare and analyze multiple groups of data, simplifies the display mode of two-dimensional nuclear magnetic resonance distribution data, and provides a new reference standard for the quantitative analysis of two-dimensional nuclear magnetic resonance data, solving the defect that the existing two-dimensional nuclear magnetic resonance data processing method is difficult to compare and analyze multiple groups of data.
Description
Technical Field
The invention relates to a processing analysis method of two-dimensional nuclear magnetic resonance data, in particular to a rock two-dimensional nuclear magnetic T 1-T2 weighted centroid fluid occurrence state analysis method.
Background
With the recent advances in exploration and development of tight reservoir technology, the importance of various non-traditional hydrocarbon resources has increased. Compared with the traditional reservoir, the development of the unconventional reservoir requires higher investment to maximize the mobility of the hydrocarbon fluid, thereby obtaining higher economic benefits. However, the current academia is not well aware of the distribution characteristics and migration mechanisms of fluids in complex reservoir pores, and therefore more innovative experimental approaches are required to deepen understanding of this field.
Unconventional reservoir rocks (such as shale and coal) have a variety of different pore types and pore fluids that exhibit diverse fluid migration behavior under in situ conditions. Currently, researchers typically employ various experimental means, such as CT (computed tomography), SEM (scanning electron microscope), and NMR (nuclear magnetic resonance), to obtain data that can directly or indirectly reflect the distribution and migration characteristics of fluids within reservoir rocks by controlling experimental environmental factors such as temperature, pressure, and the type and content of fluids in the sample. Among these commonly used experimental techniques, two-dimensional nuclear magnetic resonance (2D NMR) is a technique that is rapid, non-destructive and widely used in petrogeology, and is often used to evaluate the quantity and distribution of hydrogen-containing fluids in porous media. Compared to conventional one-dimensional nuclear magnetic resonance, the T 1 (longitudinal relaxation time) -T 2 (transverse relaxation time) two-dimensional nuclear magnetic resonance technique can provide T 1 and T 2 information simultaneously in a short time, thereby more accurately identifying multiple fluids.
Currently, two-dimensional nuclear magnetic resonance technology still has some defects in the application process, such as insufficient research on an original nuclear magnetic data processing method and lack of an analysis method universally applicable to multi-group data comparison analysis, which also limits further popularization of the two-dimensional nuclear magnetic resonance technology. Thus, solving these challenges is very urgent.
Disclosure of Invention
Aiming at the technical problems in the background art, the invention provides a rock two-dimensional nuclear magnetic T 1-T2 weighted centroid fluid occurrence state analysis method, which overcomes the defect that the existing two-dimensional nuclear magnetic resonance data processing method is difficult to carry out contrast analysis on multiple groups of data, simplifies the display mode of two-dimensional nuclear magnetic resonance distribution data, provides a new reference standard for quantitative analysis of the two-dimensional nuclear magnetic resonance data, and solves the defect that the existing two-dimensional nuclear magnetic resonance data processing method is difficult to carry out contrast analysis on multiple groups of data.
In order to solve the technical problems, the method for analyzing the occurrence state of the rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid is characterized in that firstly, two-dimensional nuclear magnetism T 1-T2 distribution data of water-bearing rock are acquired, the initial data of a nuclear magnetic spectrum chart are converted by using the proposed weighted centroid calculation method to obtain centroid coordinates, and T 1/T2 values corresponding to the centroids are calculated to analyze occurrence and dynamic migration rules of the fluid in reservoir rock.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method specifically comprises the following steps of:
1) Selecting a rock sample, preparing, cleaning and drying, recording the original quality, and acquiring the substrate T 1-T2 distribution data by using two-dimensional nuclear magnetic resonance;
2) The dried rock sample is used for a flow experiment of a fluid medium and a two-dimensional nuclear magnetic resonance test is carried out, so that a two-dimensional nuclear magnetic T 1-T2 distribution spectrogram in the experimental process is obtained;
3) Calculating the barycenter coordinates corresponding to each T 1-T2 distribution spectrogram of the rock sample by using the obtained two-dimensional nuclear magnetism T 1-T2 distribution data by using a weighted barycenter method, and calculating the T 1/T2 value corresponding to each barycenter according to the barycenter coordinates;
4) And creating a rock sample centroid T 1-T2 distribution diagram and a centroid T 1/T2 value fluctuation condition diagram, and analyzing occurrence and migration characteristics of fluid in the reservoir rock under different states.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method comprises the following specific processes of: firstly, calibrating nuclear magnetic resonance signals by using standard samples, cutting a selected rock sample into a core column, cleaning and drying to remove dust on the surface and residual water in the core column, and then performing a two-dimensional nuclear magnetic T 1-T2 test on the cleaned and dried rock sample to obtain substrate T 1-T2 distribution data of the dried rock sample.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method comprises the steps that the SR-CPMG pulse sequence suitable for a two-dimensional magnetic field is used for testing the two-dimensional nuclear magnetism T 1-T2, and the adopted relevant parameters are as follows: echo interval T E =0.132 milliseconds, echo number NECH =3788, number of scans n=32, waiting time T w =750 milliseconds, number of loop steps 30.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method comprises the following steps: the flow experiment of the rock sample fluid medium and the two-dimensional nuclear magnetism T 1-T2 test in the step 2) need to ensure that the sample signal is completely from the sample and the fluid inside the sample, and after the fluid enters and exits the sample, the fluid on the surface of the sample needs to be cleared in time to carry out the two-dimensional nuclear magnetism T 1-T2 test.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method comprises the following specific processes of: taking the two-dimensional nuclear magnetic signal quantity of the rock sample as the weight of the relaxation time of the centroid T 1 and the T 2 to determine the centroid of the T 1-T2 distribution diagram; for a data point i in the two-dimensional nuclear magnetism T 1-T2 chart, the corresponding longitudinal and transverse relaxation times can be respectively expressed as T 1i and T 2i, and the corresponding water volume is V i, and the weight corresponding to the point is:
Wherein W i in the above formula (3) represents the weight of the data point i, T i represents the relaxation time corresponding to the data point i, and V i is the two-dimensional nuclear magnetic signal quantity corresponding to the data point i;
the centroid coordinates in one dimension can be calculated by summing the weights of all points in the graph, and the calculation formula is:
D＝∑Wi (4)；
Wherein D in the above formula (4) represents a centroid coordinate position in one dimension; w i represents the weight of data point i in the two-dimensional T 1-T2 profile; for the two-dimensional nuclear magnetic T 1-T2 distribution diagram, D is the relaxation time of the centroids T 1 and T 2, so the above formulas (3) and (4) can be further converted into:
Wherein, in the formulas (5) - (6) above, T 1ce and T 2ce represent the coordinates of centroids T 1 and T 2, W 1i and W 2i represent the weights of data point i in the two dimensions of centroids T 1 and T 2, and T 1i and T 2i represent the relaxation times of centroids T 1 and T 2 corresponding to data point i, respectively; the position of the centroid of the two-dimensional nuclear magnetic T 1-T2 distribution diagram is the result of weighted average of all data points, and can be converted into a coordinate form to be expressed, and the expression is as follows:
Thus, the T 1/T2 value of the centroid can be calculated according to the coordinate value of the centroid, namely:
Wherein R T1/T2 in the above formula (8) represents the T 1/T2 value of the centroid.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method, wherein the step 4) is to develop occurrence and migration characteristic analysis of fluid in a rock sample according to the obtained centroid distribution condition and a T 1/T2 value thereof, and the specific analysis steps are as follows:
4.1 Projecting the obtained centroid coordinates into a T 1-T2 distribution diagram by taking two dimensions as coordinate axes, and marking each rock sample and the fluid state corresponding to the rock sample in the diagram;
4.2 According to the migration rule of the mass center position of the rock sample, so as to develop fluid migration characteristic analysis;
4.3 Drawing a relation diagram corresponding to the centroid coordinate T 1/T2 value and the experimental time, and analyzing the fluid occurrence characteristic according to the fluctuation condition of the centroid T 1/T2 value;
4.4 Characterizing the migration trend of the fluid in the rock sample in the pore by using the centroid migration result obtained in the step 4.2); and (3) further carrying out analysis on the evolution process of the fluid occurrence state by combining the law of fluctuation of the rock sample centroid coordinate T 1/T2 value obtained in the step 4.3) along with time, and thus, realizing comprehensive analysis on the fluid occurrence and migration characteristics in the reservoir rock.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method, wherein the fluid migration characteristics in the step 4.2) mainly comprise: the movement of the centroid along the diagonal direction of the two-dimensional nuclear magnetic T 1-T2 profile represents the fluid migration process within each stage of pore of the rock sample, wherein the upward right movement represents the fluid migration into the larger pore, and vice versa; movement of the centroid perpendicular to the diagonal of the two-dimensional nuclear magnetic T 1-T2 profile represents a change in fluid activity, wherein movement upward to the left represents a decrease in fluid activity and vice versa represents an increase in fluid activity.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method is characterized in that the fluid occurrence characteristics in the step 4.3) are mainly as follows: an increase in the centroid T 1/T2 value represents an increase in the degree of fluid binding by the aperture, and a decrease in the centroid T 1/T2 value represents a decrease in the degree of fluid binding by the aperture.
By adopting the technical scheme, the invention has the following beneficial effects:
The rock two-dimensional nuclear magnetic T 1-T2 weighted centroid fluid occurrence state analysis method is reasonable in conception, overcomes the defect that the existing two-dimensional nuclear magnetic resonance data processing method is difficult to conduct comparison analysis on multiple groups of data, simplifies the display mode of two-dimensional nuclear magnetic resonance distribution data, provides a new reference standard for quantitative analysis of the two-dimensional nuclear magnetic resonance data, and solves the defect that the existing two-dimensional nuclear magnetic resonance data processing method is difficult to conduct comparison analysis on multiple groups of data.
The weighted centroid method provided by the invention can efficiently extract and quantify signals in a plurality of groups of two-dimensional nuclear magnetic T 1-T2 distribution graphs by converting data points into centroids, has high efficiency and intuitiveness when processing two-dimensional nuclear magnetic resonance data, and overcomes the defect that the conventional data processing mode is difficult to develop quantitative comparison analysis of the plurality of groups of two-dimensional nuclear magnetic data. The invention can further analyze the state and migration process of water in the reservoir rock by utilizing the migration characteristics of the centroid position in the two-dimensional nuclear magnetism T 1-T2 distribution diagram and the fluctuation rule of the centroid T 1/T2 value. In addition, the barycenter coordinate and the barycenter T 1/T2 value can be used as a new test reference index in field engineering such as two-dimensional nuclear magnetic logging in future, so that the application of the two-dimensional nuclear magnetic resonance test in reservoir rock fluid analysis is further promoted.
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In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings which are required in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are some embodiments of the invention and that other drawings may be obtained from these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for analyzing the occurrence state of a rock two-dimensional nuclear magnetic T 1-T2 weighted centroid fluid according to the present invention;
FIG. 2 is a graph of a partial two-dimensional nuclear magnetic T 1-T2 distribution diagram (min in FIG. 2 represents minutes, i.e. time for developing a percolation experiment) of SA and SH samples in the percolation process in an embodiment related to the analysis method of the present invention for the occurrence state of rock two-dimensional nuclear magnetic T 1-T2 weighted centroid fluid;
FIG. 3 is a graph showing a two-dimensional nuclear magnetic T 1-T2 distribution of SA and SH samples after saturated water in an embodiment of the method for analyzing the occurrence state of a rock two-dimensional nuclear magnetic T 1-T2 weighted centroid fluid according to the present invention;
Fig. 4 is a distribution diagram of a centroid in a T 1-T2 diagram, which is calculated based on two-dimensional nuclear magnetism T 1-T2 distribution data in a seepage process of SA and SH samples by using a centroid method in an embodiment related to the analysis method of a rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state;
fig. 5 is a schematic diagram of fluctuation of the T 1/T2 values of the mass centers of the SA and SH samples in the imbibition experiment process in the embodiment related to the analysis method of the occurrence state of the rock two-dimensional nuclear magnetism T 1-T2 weighted mass center fluid.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention is further illustrated with reference to specific embodiments.
The rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid occurrence state analysis method provided by the embodiment overcomes the defect that the conventional data processing mode is difficult to develop the comparative analysis of quantification of a plurality of groups of two-dimensional nuclear magnetism data.
In the prior art, two-dimensional nuclear magnetic resonance data often adopt a longitudinal relaxation time T 1 and a transverse relaxation time T 2 as two coordinate axes, and a distribution spectrogram of a two-dimensional nuclear magnetic signal is drawn to display test data. Given the sensitivity of T 1 and T 2 to the corresponding nuclear magnetic spectral densities, the Bloembergen-Purcell-Bound (BPP) model is often used to analyze NMR signals:
where J (ω) is the spectral density at the resonant frequency ω, ω 0 is the resonant frequency of the system (related to the magnetic field frequency), and τ c can be calculated using the Stokes-Einstein equation:
where k is the boltzmann constant, T is absolute temperature, η is the dynamic viscosity of the fluid, and r g is the radius of rotation of the molecule.
From the theory above, it can be inferred that the distribution of the two-dimensional nuclear magnetic signal of the hydrogen-containing component in the reservoir rock in the two-test dimension T 1-T2 profile follows a specific pattern. For small molecule fluids with a low T 1/T2 ratio (i.e., the ratio of longitudinal relaxation time T 1 to transverse relaxation time T 2), they have a relatively high flowability and thus are located in regions with a lower T 1/T2 ratio and a wider range of T 1 and T 2. For macromolecular fluids with higher viscosities, they tend to exhibit higher T 1/T2 ratios and appear above the small-molecule fluid region in the T 1-T2 plot. Furthermore, for semi-solid or solid components, they are distributed in regions with higher T 1/T2 ratios and shorter T 2 values.
While prior studies have proposed various criteria for partitioning the hydrogen-containing components in the T 1-T2 plot based on the T 1、T2 values and the T 1/T2 ratios, the data analysis methods employed in the related studies conducted based on the T 1-T2 plot have focused primarily on qualitative analysis based on the proposed criteria, as well as on identifying different fluid components within the reservoir rock. The invention provides a method for calculating original two-dimensional nuclear magnetic T 1-T2 distribution data by adopting a weighted centroid method, which efficiently extracts signals in a two-dimensional nuclear magnetic T 1-T2 graph by converting data in a T 1-T2 distribution graph into centroid coordinate values, and overcomes the defect that the conventional data processing mode is difficult to develop quantitative comparison analysis of multiple groups of two-dimensional nuclear magnetic data. In addition, the state and migration process of water in the reservoir rock can be analyzed by utilizing parameters such as the mass center position, the mass center T 1/T2 value and the like, so that the application of the two-dimensional nuclear magnetic resonance experiment in reservoir rock fluid analysis can be further promoted.
As shown in fig. 1, in one embodiment of the present invention, a method for analyzing occurrence state of rock two-dimensional nuclear magnetism T 1-T2 weighted centroid fluid is disclosed, which includes the following steps:
1) Selecting a rock sample, preparing, cleaning and drying, recording the original quality, and acquiring the substrate T 1-T2 distribution data by using two-dimensional nuclear magnetic resonance; the specific process of the step 1) is as follows: before the subsequent experiment starts, firstly, calibrating nuclear magnetic resonance signals by using a standard sample; cutting selected rock samples (two in the embodiment) into core columns, cleaning and drying to remove dust on the surfaces and residual water in the core columns, and then performing a two-dimensional nuclear magnetism T 1-T2 test on the cleaned and dried rock samples to obtain substrate T 1-T2 distribution data of the dried rock samples; the substrate signal is used as the substrate signal of the rock sample in the two-dimensional nuclear magnetism T 1-T2 test of the subsequent step.
The two-dimensional nuclear magnetic T 1-T2 test performed in this embodiment uses an SR-CPMG pulse sequence suitable for a two-dimensional magnetic field, and the relevant parameters adopted are: echo interval T E =0.132 ms, echo number NECH =3788, number of scans n=32, waiting time T w =750 ms, number of loop steps 30, and two-dimensional nuclear magnetism T 1-T2 test in the present invention all uses this parameter.
According to national standard GB/T29172-2012 core analysis method, selecting, preparing and cleaning a rock sample; the specific process is as follows: the obtained rock sample (i.e. sample) is processed into a plurality of samples with the diameter of 2.5cm and the height of 5cm according to the experimental requirement, the two samples are cleaned, and the samples are dried for 48 hours at the temperature of 105 ℃ until the quality is not changed, so that the residual water in the two samples is removed.
2) The dried rock sample is used for flow experiments of fluid media such as oil, water and the like and two-dimensional nuclear magnetic resonance tests are carried out, and a two-dimensional nuclear magnetic T 1-T2 distribution spectrogram in the experimental process is obtained; the flow experiment of the rock sample fluid medium and the two-dimensional nuclear magnetism T 1-T2 test thereof need to ensure that the sample signal is completely from the sample and the fluid inside the sample, and after the fluid enters and exits the sample, the fluid on the surface of the sample needs to be cleared in time and then the two-dimensional nuclear magnetism T 1-T2 test is carried out.
3) Calculating the barycenter coordinates corresponding to each T 1-T2 distribution spectrogram of the rock sample by using the obtained two-dimensional nuclear magnetism T 1-T2 distribution data by using a weighted barycenter method, and calculating the T 1/T2 value corresponding to each barycenter according to the barycenter coordinates;
Wherein, this step 3) requires taking the two-dimensional nuclear magnetic signal quantity of the rock sample as the weight of the relaxation times of T 1 and T 2 to determine the centroid of the T 1-T2 distribution map; for a data point i in the two-dimensional nuclear magnetism T 1-T2 chart, the corresponding longitudinal and transverse relaxation times can be respectively expressed as T 1i and T 2i, and the corresponding water volume is V i, and the weight corresponding to the point is:
Wherein W i in the above formula (3) represents the weight of the data point i; t i represents the relaxation time corresponding to data point i; v i is the two-dimensional nuclear magnetic semaphore corresponding to data point i.
The centroid coordinates in one dimension can be calculated by summing the weights of all points in the graph, and the calculation formula is:
D＝∑Wi (4)；
Wherein D in the above formula (4) represents a centroid coordinate position in one dimension; w i represents the weight of data point i in the two-dimensional T 1-T2 profile. For the two-dimensional nuclear magnetic T 1-T2 profile, D is the relaxation times of T 1 and T 2, so the above equations (3) and (4) can be further converted into:
Wherein T 1ce and T 2ce in formulas (5) - (6) above represent the T 1 and T 2 coordinates of the centroid, respectively; w 1i and W 2i represent weights for data point i in both dimensions T 1 and T 2; t 1i and T 2i represent T 1 and T 2 relaxation times corresponding to data point i. The position of the centroid of the two-dimensional nuclear magnetic T 1-T2 distribution diagram is the result of weighted average of all data points, and can be converted into a coordinate form to be expressed in the following expression mode:
Thus, the T 1/T2 value of the centroid can be calculated according to the coordinate value of the centroid, namely:
Wherein R T1/T2 in the above formula (8) represents the T 1/T2 value of the centroid.
4) And creating a rock sample centroid T 1-T2 distribution diagram and a centroid T 1/T2 value fluctuation condition diagram, and analyzing occurrence and migration characteristics of fluid in the reservoir rock under different states.
In the step 4), occurrence and migration characteristic analysis of fluid in the rock sample is carried out according to the obtained centroid distribution condition and the T 1/T2 value thereof, and the specific analysis steps are as follows:
4.1 Projecting the obtained centroid coordinates into a T 1-T2 distribution diagram by taking two dimensions as coordinate axes, and marking each rock sample and the fluid state corresponding to the rock sample in the diagram;
4.2 According to the migration rule of the mass center position of the rock sample, so as to develop fluid migration characteristic analysis; wherein movement of the centroid along the diagonal direction of the T 1-T2 plot represents the fluid migration process within each stage of pore of the rock sample; movement of the centroid perpendicular to the diagonal of the T 1-T2 plot represents the change in fluid activity that exists in the experiment;
4.3 Drawing a relation diagram corresponding to the centroid coordinate T 1/T2 value and the experimental time, and analyzing the fluid occurrence characteristic according to the fluctuation condition of the centroid T 1/T2 value; wherein an increase in the centroid T 1/T2 value represents an increase in the degree of fluid binding by the aperture and a decrease in the centroid T 1/T2 value represents a decrease in the degree of fluid binding by the aperture;
4.4 Characterizing the migration trend of the fluid in the rock sample in the pore by using the centroid migration result obtained in the step 4.2); and (3) further carrying out analysis on the evolution process of the fluid occurrence state by combining the law of fluctuation of the rock sample centroid coordinate T 1/T2 value obtained in the step 4.3) along with time, and thus, realizing comprehensive analysis on the fluid occurrence and migration characteristics in the reservoir rock.
The following is a further description of the present invention with reference to specific examples.
This example takes the experimental procedure of spontaneous imbibition of cores of sandstone and shale and fully saturated distilled water as an example. In the experiment, room temperature was maintained at 20℃and the pressure was normal atmospheric pressure (0.1 MPa). Samples included 2 cylindrical cores 5cm long and 2.5cm in diameter to conduct experiments, labeled SA (sandstone sample) and SH (shale sample).
In the spontaneous imbibition experiment, two samples were tested for two-dimensional nuclear magnetism T 1-T2 using a plurality of time nodes to obtain corresponding T 1-T2 distribution diagrams, wherein the T 1-T2 distribution diagrams of 90 minutes, 4580 minutes and 9980 minutes and SH at 90 minutes, 1070 minutes and 4560 minutes after the SA experiment is started are shown in FIG. 2. Thereafter, the two samples were transferred to a pressurizing pump, distilled water was injected into the pump, and the pressure was increased to 30MPa and maintained for 24 hours, to prepare a sample of completely saturated water. Two samples in the fully saturated water state were subjected to a line two-dimensional nuclear magnetism T 1-T2 test, and a T 1-T2 distribution diagram of the corresponding state was obtained as shown in FIG. 3. As can be seen from fig. 2 and 3, the signal of SA is distributed in the narrowband region of T 1 =1-100 ms and T 2 =0.5-500 ms, while the signal of SH is distributed in the elliptical region of T 1 =0.3-30 ms and T 2 =0.2-20 ms. Compared with SA, the relaxation times of T 1 and T 2 corresponding to SH are obviously shorter, and the characteristics of numerous shale pore development are reflected.
The two-dimensional nuclear magnetism T 1-T2 distribution data obtained in the imbibition and saturation experiment can be converted into centroid coordinates by using the formulas (3) - (7). And projecting the obtained barycenter coordinates into the T 1-T2 distribution diagram, so that the migration condition of the barycenter in the T 1-T2 distribution diagram in the whole experimental process can be obtained, as shown in fig. 4. According to the formula (8), the value of T 1/T2 corresponding to the centroid can be further calculated, so as to obtain the fluctuation process of the value of the centroid T 1/T2 in the experiment, as shown in fig. 5.
According to the information provided by fig. 4 and 5, the occurrence and migration characteristic analysis of water in the rock sample can be performed. Fig. 4 shows that the centroids of the two rock samples fall mainly in the range of 10-1000ms for T 1 and T 2 relaxation times. Throughout the experiment, the centroids of SA and SH moved primarily in the diagonal (T 1＝T2 line) direction, with the centroid of SA moving up and right and the centroid of SH moving down and left. From the characteristic of centroid migration, it can be seen that the water in SA tends to migrate to the macropores during spontaneous imbibition, while the water in SH tends to be small Kong Yunyi, and the characteristic of no significant deviation from the diagonal is adopted, and this phenomenon follows the law of two types of reservoir rocks in the water entering process, and can be used for researching the distribution characteristics of water in the reservoir rocks.
The ratio of centroid T 1/T2 of the two samples was mainly between 0.5 and 2.0, consistent with the expected relaxation properties of distilled water. During the experimental process, the centroid T 1/T2 values of the two rock samples show a trend of increasing first and then stabilizing, and finally approach to the T 1/T2 value in the saturated state. The change rule shows the trend that the binding degree of water in the pores of the rock sample gradually increases along with saturation, and accords with the filling rule of pore water in the process of imbibition to saturation. It follows that centroid T 1/T2 values are useful in studying the presence of water in reservoir rock pores.
The invention overcomes the defect that the existing two-dimensional nuclear magnetic resonance data processing method is difficult to carry out contrast analysis on multiple groups of data, simplifies the display mode of two-dimensional nuclear magnetic resonance distribution data, provides a new reference standard for quantitative analysis of the two-dimensional nuclear magnetic resonance data, and solves the defect that the existing two-dimensional nuclear magnetic resonance data processing method is difficult to carry out contrast analysis on multiple groups of data.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
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