Method and system for calculating high TOC oil shale hydrocarbon generation pressurization contribution rate

Abstract

The invention relates to the technical field of oil exploitation, in particular to a method and system for calculating the hydrocarbon generation pressurization contribution rate of high-TOC oil shale, and the method comprises the steps: calculating the TOC content of the oil shale; establishing a target longitudinal and transverse wave velocity relational expression; reconstructing the longitudinal wave velocity of the high TOC oil shale based on the target longitudinal and transverse wave velocity relational expression to obtain a reconstructed longitudinal wave velocity; constructing a pressure prediction basic model, and calculating the pore pressure and background pressure of the high-TOC oil shale under-compaction cause based on the pressure prediction basic model and the reconstructed longitudinal wave velocity; based on the pore pressure and the background pressure, obtaining a hydrocarbon generation supercharging pressure coefficient difference, and obtaining a speed difference between the actually measured sound wave speed and the reconstructed longitudinal wave speed; and performing rendezvous analysis on the speed difference and the pressure coefficient difference to obtain a target fitting formula, and calculating the contribution of hydrocarbon generation pressurization based on the fitting formula. According to the method, quantitative calculation of the hydrocarbon generation pressurization contribution of the high-TOC oil shale and high-precision prediction of the formation pore pressure are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of oil extraction, and in particular to a method and a system for calculating the contribution rate of hydrocarbon generation and pressurization of high-TOC oil shale. Background Art

[0002] The Beibu Gulf Basin, located in the South China Sea, is a proven hydrocarbon-rich sag and a rapidly subsiding Cenozoic sedimentary basin. The abnormally high pressure in the second section of the Liushagang Formation in the deep and medium layers is one of its important characteristics. Previous studies generally believed that this abnormally high pressure was mainly caused by the extremely thick undercompacted mudstone formed by rapid sedimentation, and the weak tectonic activity in the later period played an important role in maintaining this abnormally high pressure. For clastic rock formations, the traditional mudstone undercompacted model has shown relatively high accuracy in pressure prediction. However, with the continuous expansion of the exploration field and the gradual increase in the number of exploration strata, especially the development of oil shale exploration drilling in the past two years, it has been found that in addition to the undercompacted cause, the oil shale in the second section of the Liushagang Formation in the Southwest Weixi Depression also has a non-undercompacted abnormal pressure cause. When relying solely on the mudstone undercompacted model for pre-drilling pressure prediction, there is a large error between the predicted pressure obtained by the oil shale formation and the measured formation pressure, which poses new challenges to the pressure prediction in the shale oil field. For the Southwest Wei Depression, the study of abnormal pressure in oil shale is a completely new field. To meet this challenge, the researchers first determined the cause of abnormal pressure by velocity-density intersection analysis; secondly, they used acoustic wave curve reconstruction to calculate the proportion of undercompaction-caused pressure in the total pressure; finally, they established a shale oil hydrocarbon generation pressurization contribution template based on actual pressure measurement points. This research method has been successfully applied in the pre-drilling pressure prediction and while-drilling pressure analysis of new wells in the Southwest Wei Depression, and has shown high accuracy, providing technical support for the discovery of shale oil, as well as reasonable wellbore structure design and improved drilling safety.

[0003] Despite this, some problems were still encountered during the actual drilling process. For example, when drilling the first shale oil parameter well W1 in China's offshore, although the pre-drilling pressure prediction showed high accuracy in the upper sequence of the second section of the stream and above, complex well conditions appeared in the oil shale section of the lower sequence of the second section of the stream. The formation pressure coefficient judged by the comprehensive well conditions was significantly higher than the pre-drilling predicted pressure, and there was a large deviation in the formation pressure prediction. The same situation also occurred in the subsequent drilling of the W4 well. This shows that for the oil shale section of the lower sequence of the second section of the stream, there is a large error in the pressure calculation according to the mudstone under-compaction model, and there are certain contradictions in the abnormal pressure formation mechanism. In addition, the drilling operation window of the pore pressure and fracture pressure of the oil shale formation in this section is very narrow, and the accuracy of pressure prediction is extremely high.

[0004] Therefore, in response to the above problems, it is necessary to conduct research on the cause judgment and prediction method of abnormal pressure in oil shale formations, aiming to form a set of technical systems to provide technical support for subsequent oil shale drilling. However, current research still cannot accurately calculate the contribution of high TOC (total organic carbon) oil shale to hydrocarbon generation and pressure increase, which leads to large errors in the predicted pressure of high TOC oil shale. Therefore, further optimizing and improving the prediction method of abnormal pressure in oil shale formations is still the focus of current research. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for calculating the contribution rate of hydrocarbon generation and pressurization of high TOC oil shale in order to solve at least one of the above technical problems.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0007] A method for calculating the contribution rate of hydrocarbon generation and pressurization of high TOC oil shale comprises the following steps:

[0008] Calculate the TOC content of oil shale;

[0009] Conduct intersection analysis of P-wave velocity and S-wave velocity for mudstone and immature oil shale in the same region and the same formation, and establish the target P-wave and S-wave velocity relationship.

[0010] Based on the target P-wave and S-wave velocity relationship, the P-wave velocity of the high TOC oil shale is reconstructed to obtain a reconstructed P-wave velocity;

[0011] Constructing a basic model for pressure prediction, and calculating the pore pressure background pressure of the high TOC oil shale due to undercompaction based on the basic model for pressure prediction and the reconstructed P-wave velocity;

[0012] The hydrocarbon generation pressure coefficient difference is obtained based on the pore pressure background pressure, and the velocity difference between the measured acoustic wave velocity and the reconstructed longitudinal wave velocity is obtained; the velocity difference and the pressure coefficient difference are subjected to intersection analysis to obtain a target fitting formula, and the contribution of hydrocarbon generation pressure increase is calculated based on the fitting formula.

[0013] Further, calculating the TOC content of oil shale includes: calculating the TOC content of oil shale based on acoustic wave and resistivity logging data combined with geochemical analysis, specifically including the following steps:

[0014] Acquire acoustic transit time and resistivity data through logging while drilling or Grand Slam technology;

[0015] The acoustic time difference curve and resistivity curve are superimposed and displayed in reverse scale;

[0016] Calculate the estimated value of TOC content based on the acoustic time difference and the offset amplitude of resistivity relative to their respective base value lines;

[0017] The TOC content estimate is calibrated using TOC data obtained from geochemical analysis.

[0018] Furthermore, the target longitudinal and transverse wave velocity relationship is:

[0019] Vp=1.33078*Vs+1154

[0020] Among them, Vp is the longitudinal wave velocity and Vs is the shear wave velocity.

[0021] Furthermore, a basic model for pressure prediction is constructed, including:

[0022] Analyze the acoustic logging data of rocks at different depths in the target sedimentary basin to obtain the compaction trend of rock velocity with depth in the area;

[0023] The pressure prediction basic model is constructed based on the relationship between the target velocity difference and the pressure coefficient of the target sedimentary basin and the compaction trend.

[0024] Furthermore, obtaining the hydrocarbon generation boost pressure coefficient difference includes:

[0025] Based on the reconstructed P-wave velocity, a pore pressure background value is calculated without the effect of hydrocarbon generation pressurization to obtain a reconstructed pore pressure background pressure;

[0026] The actual measured pore pressure is subtracted from the reconstructed pore pressure background pressure to obtain the hydrocarbon generation pressurization pressure coefficient difference.

[0027] A system for calculating the contribution rate of hydrocarbon generation and pressurization of high TOC oil shale, comprising:

[0028] TOC content calculation module, used to calculate the TOC content of oil shale;

[0029] The velocity relationship building module is used to conduct intersection analysis of P-wave velocity and S-wave velocity for mudstone and immature oil shale in the same layer in the same area, and establish the target P-wave and S-wave velocity relationship;

[0030] A longitudinal wave velocity reconstruction module is used to reconstruct the longitudinal wave velocity of the high TOC oil shale based on the target longitudinal and transverse wave velocity relationship to obtain a reconstructed longitudinal wave velocity;

[0031] The hydrocarbon generation pressurization contribution rate calculation module is used to construct a basic model for pressure prediction, calculate the pore pressure background pressure caused by undercompaction of high TOC oil shale based on the basic model for pressure prediction and the reconstructed longitudinal wave velocity; obtain the hydrocarbon generation pressurization pressure coefficient difference based on the pore pressure background pressure, and obtain the velocity difference between the measured acoustic wave velocity and the reconstructed longitudinal wave velocity; perform intersection analysis on the velocity difference and the pressure coefficient difference to obtain a target fitting formula, and calculate the contribution of hydrocarbon generation pressurization based on the fitting formula.

[0032] Furthermore, the target longitudinal and transverse wave velocity relationship is:

[0033] Vp=1.33078*Vs+1154

[0034] Among them, Vp is the longitudinal wave velocity and Vs is the shear wave velocity.

[0035] An electronic device comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, any of the above methods for calculating the pressurization contribution rate of hydrocarbon generation in high TOC oil shale is implemented.

[0036] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements any of the above methods for calculating the pressurization contribution rate of hydrocarbon generation in high TOC oil shale.

[0037] A computer program product includes a computer program, characterized in that when the computer program is executed by a processor, the steps of the method for calculating the pressurization contribution rate of hydrocarbon generation in high TOC oil shale as described above are implemented.

[0038] The present invention proposes an innovative solution to the problem that the pressure prediction method in the prior art cannot accurately predict and calculate the pressure increase contribution of high TOC oil shale hydrocarbon generation, and there is a large error in the predicted pressure. Compared with the prior art, the present invention has the following significant advantages:

[0039] First, the present invention can achieve real-time prediction before drilling and during drilling. This feature enables instant acquisition and analysis of data during drilling operations, and timely adjustment of drilling strategies, thereby improving drilling efficiency and safety.

[0040] Secondly, the present invention can accurately determine the causes of abnormal pressure in mudstone, immature oil shale and high TOC oil shale. By carefully analyzing the causes of pressure in different lithologies, the present invention provides more accurate geological information for geological exploration and oil and gas resource development.

[0041] Furthermore, the present invention realizes the quantitative calculation of the pressurization contribution of high TOC oil shale and the prediction of formation pressure. This breakthrough makes the exploration and development of oil and gas resources more targeted and accurate, and provides strong support for the efficient development of oil and gas fields.

[0042] In addition, the present invention has strong adaptability to oil shale targets. Whether in complex geological environments or in oil shale formations at different depths, the present invention can provide reliable pressure prediction and hydrocarbon generation pressure increase contribution calculation results.

[0043] The present invention not only breaks through the limitations of the causes and prediction methods of abnormal pressure of under-compaction mudstone, but also realizes high-precision prediction of formation pore pressure of high-TOC oil shale, providing more reliable technical support for the exploration and development of oil and gas resources. It has broad application prospects and important practical value in the field of oil and gas resource exploration and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A flow chart of a method for calculating the contribution rate of hydrocarbon generation and pressurization of high TOC oil shale according to an embodiment of the present invention;

[0045] Figure 2 A flow chart of a method for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization according to another embodiment of the present invention;

[0046] Figure 3 A schematic diagram of obtaining reconstructed longitudinal wave velocity according to an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of a basic model for pressure prediction according to an embodiment of the present invention;

[0048] Figure 5 Schematic diagram of calculating the contribution of hydrocarbon generation pressure increase based on the fitting formula;

[0049] Figure 6 A system structure diagram for calculating the pressurization contribution rate of high TOC oil shale hydrocarbon generation according to an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The content of the present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only to enable those skilled in the art to better understand and thus implement the content of the present invention, rather than implying any limitation on the scope of the present invention.

[0051] As used herein, the term “including” and variations thereof are to be interpreted as open-ended terms meaning “including, but not limited to.” The term “based on” is to be interpreted as “based, at least in part, on.” The terms “one embodiment” and “an embodiment” are to be interpreted as “at least one embodiment.”

[0052] Embodiment 1

[0053] Figure 1 A flow chart of a method for calculating the contribution rate of hydrocarbon generation and pressurization of high TOC oil shale according to an embodiment of the present invention; Figure 3 A schematic diagram of obtaining reconstructed longitudinal wave velocity according to an embodiment of the present invention; Figure 4 A schematic diagram of a basic model for pressure prediction according to an embodiment of the present invention; Figure 5 Schematic diagram of calculating the contribution of hydrocarbon generation pressure increase based on the fitting formula. Figure 1 , 3 -5, according to one embodiment of the present invention, a method for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization includes the following steps:

[0054] Step S102: Calculate the TOC content of oil shale;

[0055] In the process of oil exploration and development, it is crucial to understand the total organic carbon (TOC) content in oil shale. This can not only help us evaluate the oil storage potential of oil shale, but also provide important basis for subsequent mining and utilization.

[0056] Step S104: performing intersection analysis of the P-wave velocity and S-wave velocity on the mudstone and immature oil shale in the same region and the same formation, and establishing a target P-wave velocity and S-wave velocity relationship.

[0057] Through the intersection analysis of the P-wave velocity and S-wave velocity of mudstone and oil shale in the same area and the same formation, it is found that the P-wave and S-wave change distribution trend of immature oil shale on the intersection diagram is consistent with that of mudstone due to the lack of hydrocarbon fluid, and follows the same change law. The P-wave and S-wave data of mudstone and immature oil shale in this area can be used to fit and establish the target P-wave and S-wave velocity relationship.

[0058] Step S106: reconstruct the P-wave velocity of high TOC oil shale based on the target P-wave and S-wave velocity relationship.

[0059] High TOC oil shale contains abundant hydrocarbons. These hydrocarbon fluids occupy a certain space in the rock pores, resulting in a decrease in the effective elastic modulus of the rock skeleton. The presence of hydrocarbon fluids may also cause changes in the pressure distribution inside the rock, further affecting the propagation speed of the rock sound wave.

[0060] Due to the contribution of hydrocarbon generation and pressurization, the measured P-wave velocity and density of high TOC oil shale are often low due to the presence of hydrocarbons in the fluid, which is significantly different from the acoustic logging data of conventional mudstone and immature source rock. In the crossplot, the data points of high TOC oil shale usually fall below the loading curves of mudstone and immature source rock, forming an obvious deviation area. The presence of hydrocarbon fluid significantly reduces the P-wave velocity of high TOC oil shale. This is because P-waves mainly propagate along the rock skeleton, and the presence of hydrocarbon fluids weakens the elastic modulus of the rock skeleton. Unlike P-waves, hydrocarbon fluids have relatively little effect on the S-wave velocity of high TOC oil shale. S-waves mainly propagate along the shear direction of the rock and are less affected by fluids. In order to eliminate the influence of hydrocarbon fluids on P-wave velocity in high TOC oil shale, for high TOC oil shale, we use its S-wave velocity data and reconstruct the reconstructed P-wave velocity that is not affected by hydrocarbon fluids according to the established target P-S wave velocity relationship. The reconstructed P-wave velocity is closer to the real velocity of the rock skeleton and can more accurately reflect the physical properties of the rock.

[0061] Step S108: construct a basic model for pressure prediction, and calculate the pore pressure background pressure of the high TOC oil shale caused by undercompaction based on the basic model for pressure prediction and the reconstructed longitudinal wave velocity.

[0062] By reconstructing the P-wave velocity, combined with the compaction trend of velocity variation with depth in the Southwest Wei Sag and the relationship between velocity difference and pressure coefficient, a basic model for pressure prediction is constructed, and the pore pressure background pressure of high TOC oil shale due to undercompaction is calculated. Through the basic model for pressure prediction, we can calculate the pore pressure of high TOC oil shale at different depths. Among these pore pressures, the part caused by undercompaction is the pore pressure background pressure due to undercompaction. Undercompaction refers to the failure of rocks to reach the normal degree of compaction during the compaction process due to some reasons (such as the presence of hydrocarbon fluids, the particularity of the rock skeleton, etc.), resulting in the retention of pore space and the formation of higher pore pressure. In the calculated pore pressure, the part caused by other factors (such as tectonic stress, fluid expansion, etc.) is removed to obtain the pore pressure background pressure due to undercompaction.

[0063] Step S110: obtaining a hydrocarbon generation pressure coefficient difference based on the pore pressure background pressure, and obtaining a velocity difference between the measured acoustic wave velocity and the reconstructed longitudinal wave velocity;

[0064] The velocity difference and the pressure coefficient difference are intersected and analyzed to obtain the target fitting formula, and the contribution of hydrocarbon generation to pressure increase is calculated based on the fitting formula.

[0065] In this implementation, the velocity difference between the measured acoustic wave velocity and the reconstructed longitudinal wave velocity of the high TOC oil shale section is statistically analyzed. This velocity difference represents the velocity contribution of the hydrocarbon generation and pressurization part of the high TOC oil shale. The actual pressure measurement data of the wells that have been drilled is subtracted from the pore pressure background pressure of the undercompacted high TOC oil shale calculated by the reconstructed longitudinal wave velocity to obtain the hydrocarbon generation and pressurization pressure coefficient difference. Through regression analysis and other methods, we can derive the fitting formula between the velocity difference and the pressure coefficient difference. This formula can be used to quantify the impact of hydrocarbon generation and pressurization on the acoustic wave velocity and pore pressure. Using the fitting formula, we can calculate the specific contribution of hydrocarbon generation and pressurization in high TOC oil shale based on the measured velocity difference or pressure coefficient difference.

[0066] The present invention reconstructs the longitudinal wave velocity of high-TOC oil shale and combines it with a pressure prediction model to achieve quantitative calculation of the contribution of hydrocarbon generation to pressurization in high-TOC oil shale and high-precision prediction of formation pore pressure, breaking through the limitations of traditional prediction methods, enhancing the adaptability of oil shale targets, and realizing real-time prediction before drilling and during drilling.

[0067] According to an embodiment of the present invention, step S102 includes: calculating the TOC content of oil shale based on acoustic wave and resistivity logging data combined with geochemical analysis, specifically including the following steps:

[0068] Step S1022, obtaining acoustic wave time difference and resistivity data by logging while drilling or Grand Slam technology;

[0069] Step S1024, superimposing and displaying the acoustic time difference curve and the resistivity curve in reverse scale;

[0070] Step S1026, calculating the estimated value of TOC content according to the acoustic wave time difference and the offset amplitude of the resistivity relative to the respective base value lines;

[0071] Step S1028, calibrating the TOC content estimation value using the TOC data obtained by geochemical analysis.

[0072] In this embodiment, the TOC content of oil shale is calculated by data acquisition, curve superposition, calculation of TOC value, and geochemical analysis calibration, specifically including: first, the acoustic time difference curve and resistivity curve data are obtained by logging while drilling or Grand Slam. These data reflect the physical properties of the rock, including porosity, permeability, and conductivity. Then, the acoustic time difference curve and the resistivity curve are reversely scaled and superimposed. In rocks lacking organic matter (i.e., no TOC or low TOC), the two curves have good superposition due to the relatively uniform physical properties of the rock. In high-TOC oil shale rich in organic matter, the presence of organic matter changes the physical properties of the rock, resulting in poor superposition of the two curves and differences. Then, based on the offset amplitude of the acoustic time difference and resistivity relative to their respective base lines, we can calculate the TOC value, i.e., the estimated TOC content. The base line represents the baseline value of the rock physical properties in the area. Finally, the TOC data obtained by geochemical analysis is used to calibrate the previous calculation results. Geochemical analysis is the most direct and accurate method to determine the organic matter content in rocks, but it is more expensive and time-consuming than well logging. Therefore, quickly calculating TOC values ​​through well logging methods and combining them with geochemical analysis for calibration can greatly improve work efficiency and accuracy.

[0073] The present invention obtains the acoustic time difference and resistivity data through the logging while drilling or Grand Slam technology, calculates the TOC content estimation value of the oil shale by using the reverse scale superposition display of the two curves and the offset amplitude relative to the base value line, and calibrates it through geochemical analysis, thereby realizing efficient and accurate calculation of the TOC content of the oil shale, which not only reduces the cost but also improves the work efficiency.

[0074] According to an embodiment of the present invention, in step S104, the target longitudinal and transverse wave velocity relationship is:

[0075] Vp=1.33078*Vs+1154

[0076] Among them, Vp is the longitudinal wave velocity and Vs is the shear wave velocity.

[0077] Intersection analysis is a method of graphically displaying the relationship between two variables. By drawing a scatter plot or a trend line, the changing trend and correlation between the variables can be intuitively observed. In this embodiment, longitudinal wave velocity and shear wave velocity are used as two variables to perform intersection analysis on mudstone and immature oil shale. Mudstone, as a common sedimentary rock, has relatively stable physical properties, and there is a certain relationship between longitudinal wave velocity and shear wave velocity. On the intersection diagram, the longitudinal and shear wave velocity points of mudstone show a certain distribution trend, which reflects the uniformity and stability of the internal structure of mudstone. Since immature oil shale has not experienced the generation and migration of hydrocarbon fluids, its physical properties are similar to those of mudstone, but it contains certain organic matter. On the intersection diagram, the longitudinal and shear wave velocity points of immature oil shale are consistent with the distribution trend of mudstone, indicating that the two have certain similarities in physical properties. By performing intersection analysis on mudstone and immature oil shale in the same stratum in the same region, we found that the longitudinal and shear wave velocity distribution trends of the two on the intersection diagram are the same. Therefore, we can use this characteristic to establish the target P- and S-wave velocity relationship by fitting the P- and S-wave data of mudstone and immature oil shale.

[0078] The present invention cross-analyzes the P-wave velocity and S-wave velocity of mudstone and immature oil shale, utilizes the consistency of their distribution trends on the cross-plot, successfully fits the data and establishes the target P-wave and S-wave velocity relationship, thereby effectively revealing the similarity between the two rocks in physical properties and providing a powerful tool for related geological analysis.

[0079] According to one embodiment of the present invention, step S108 includes:

[0080] Step S1082: Analyze the acoustic logging data of rocks at different depths in the target sedimentary basin to obtain the compaction trend of rock velocity with depth in the region;

[0081] Step S1084: construct a basic model for pressure prediction based on the relationship between the target velocity difference and the pressure coefficient and the compaction trend of the target sedimentary basin.

[0082] In this embodiment, first, the reconstructed P-wave velocity of high TOC oil shale is obtained, because the reconstructed P-wave velocity can reflect the physical properties of the rock, including its porosity and compaction state, etc., and provide an important basis for subsequent analysis. Then, a basic model for pressure prediction is constructed according to the compaction trend of velocity variation with depth in the Weixinan Depression (target sedimentary basin). The Weixinan Depression is an area with complex geological conditions, and its velocity field is affected by many factors. By deeply studying the compaction trend of velocity variation with depth in this area, a pressure prediction model that can reflect the geological characteristics of the area can be established. This model will serve as an important tool for subsequent calculation of pore pressure background pressure. Then, the relationship between velocity difference and pressure coefficient is used to further improve the pressure prediction model. Velocity difference refers to the difference between the actual measured P-wave velocity and the P-wave velocity under the normal compaction trend, which reflects the compaction state of the rock and the change of pore pressure. The pressure coefficient is a parameter that reflects the relationship between pore pressure and hydrostatic pressure. By combining velocity difference with pressure coefficient, a background pressure model that can more accurately predict pore pressure can be established. Finally, the constructed pressure prediction basic model is used to calculate the pore pressure background pressure caused by undercompaction of high TOC oil shale.

[0083] The present invention constructs a basic model for pressure prediction by analyzing the acoustic logging data of rocks in the target sedimentary basin, and improves the model by using the relationship between the target velocity difference and the pressure coefficient, so as to accurately predict the pore pressure background pressure caused by undercompaction of high TOC oil shale, providing an important basis for geological exploration and development.

[0084] According to an embodiment of the present invention, in step S110, obtaining the hydrocarbon generation boost pressure coefficient difference includes:

[0085] Step 1: Based on the reconstructed P-wave velocity, the pore pressure background value without hydrocarbon generation pressurization is calculated to obtain the reconstructed pore pressure background pressure;

[0086] Step 2: Subtract the actual measured pore pressure from the reconstructed pore pressure background pressure to obtain the hydrocarbon generation pressure coefficient difference.

[0087] In this embodiment, we can obtain the actual pore pressure data of the high TOC oil shale section through pressure measurement during drilling. Based on the reconstructed P-wave velocity and known rock physics relationship, we can calculate the pore pressure background value without hydrocarbon generation pressurization. The actual measured pore pressure is subtracted from the reconstructed pore pressure background value to obtain the hydrocarbon generation pressurization pressure coefficient difference. This difference reflects the actual contribution of hydrocarbon generation pressurization to the pore pressure.

[0088] The present invention calculates the pore pressure background value under the reconstructed P-wave velocity and subtracts it from the actually measured pore pressure to accurately obtain the hydrocarbon generation pressurization pressure coefficient difference, thereby achieving a quantitative evaluation of the contribution of hydrocarbon generation pressurization to the pore pressure and further improving the accuracy of pore pressure prediction in high TOC oil shale formations.

[0089] Embodiment 2

[0090] Figure 2 FIG. 1 is a flow chart of a method for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization according to another embodiment of the present invention. Figure 2-5 As shown, according to one embodiment of the present invention, a method for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization includes the following steps:

[0091] Step S202: Calculate the TOC content of oil shale based on the acoustic wave and resistivity logging data combined with geochemical analysis, and use the acoustic wave and resistivity curves while drilling or Grand Slam to overlay the two curves in reverse scales. In rocks lacking organic matter (no TOC or low TOC), the two curves have good superposition. In organic matter-rich and high-TOC oil shale, the two curves have poor superposition and differences. Calculate the TOC value based on the acoustic wave time difference and the amplitude of the resistivity deviation from the respective base value lines, and calibrate the calculation result with the TOC of geochemical analysis;

[0092] Step S204: Through the cross-plot analysis of the P-wave velocity and S-wave velocity of the mudstone and oil shale in the same region and the same formation, it is found that the immature oil shale has the same P-wave and S-wave variation distribution trend as the mudstone due to the lack of hydrocarbon fluid, and follows the same variation law. The P-wave and S-wave velocity relationship can be established by fitting the P-wave and S-wave data of the mudstone and the immature oil shale in the region; the specific formula is:

[0093] Vp=1.33078*Vs+1154

[0094] Among them, Vp is the longitudinal wave velocity and Vs is the shear wave velocity.

[0095] Step S206: Since the oil shale skeleton contains TOC (total organic carbon, the same below) and there is a contribution of hydrocarbon generation pressurization, the oil shale with high TOC content has a low measured velocity density due to the presence of hydrocarbon substances in the fluid, and deviates from the loading curves of mudstone and immature source rock as a whole and falls below their loading curves. The presence of hydrocarbon fluid reduces the longitudinal wave velocity of the oil shale, but has little effect on the shear wave velocity of the oil shale. Therefore, in order to eliminate the influence of hydrocarbon fluid in high TOC oil shale on the longitudinal wave velocity, the shear wave velocity of the high TOC oil shale is reconstructed according to the longitudinal and shear wave velocity relationship fitted by the mudstone and low TOC oil shale in step S204.

[0096] Step S208: using the high TOC oil shale longitudinal wave velocity reconstructed in step S206, and according to the compaction trend of velocity variation with depth in the Weixinan Sag and the pressure prediction basic model constructed by velocity difference and pressure coefficient, calculate the pore pressure background pressure caused by undercompaction of the high TOC oil shale;

[0097] Among them, the basic model for pressure prediction is the correspondence between the velocity difference (the difference between the formation velocity and the velocity compaction trend) and the pressure coefficient corresponding to different positions and different pressure causes in the basin. Under the condition of the same velocity difference between the source and edge of the basin due to undercompacted genesis, the pressure coefficient at the edge of the basin is high; while compared with the source of the basin and the center of the basin, under the same velocity difference, the pressure coefficient at the center of the basin is higher than that at the edge of the basin; for the comparison between the model of undercompacted genesis and the model with non-undercompacted genesis, under the same velocity difference, the pressure coefficient of the model with non-undercompacted genesis is significantly higher than that of the model with undercompacted genesis.

[0098] Step S210: Count the velocity difference between the measured acoustic wave velocity and the reconstructed longitudinal wave velocity of the high TOC oil shale section. The velocity difference should represent the velocity contribution of the high TOC oil shale hydrocarbon generation pressurization part. Then, the actual pressure measurement data of the well and the pore pressure background pressure of the high TOC oil shale undercompaction calculated by the reconstructed longitudinal wave velocity are subtracted to obtain the hydrocarbon generation pressurization pressure coefficient difference. Then, the velocity difference and the pressure coefficient difference are intersected and analyzed to fit the formula to calculate the contribution of hydrocarbon generation pressurization.

[0099] The present invention can realize the prediction before drilling and while drilling, can realize the cause of abnormal pressure of mudstone, immature oil shale and high TOC oil shale, and can realize the quantitative calculation and prediction of the contribution of hydrocarbon generation and pressurization of high TOC oil shale, and has strong adaptability to oil shale targets. The present invention breaks through the cause and prediction method of abnormal pressure of under-compaction mudstone, and realizes the high-precision formation pore pressure prediction of high TOC oil shale.

[0100] Embodiment 3

[0101] In this embodiment, for the W5, W6 and W8 wells drilled in the oil shale target layer, the method for calculating the high TOC oil shale hydrocarbon generation pressurization contribution rate of the present invention is used to predict the formation pore pressure of the three wells. The prediction results are shown in Table 1.

[0102]

[0103] Table 1 Comparison of data on the prediction of high TOC oil shale formation pressure coefficient using the traditional prediction method and the method of the present invention

[0104] Table 1 is a data comparison table of the pressure coefficient of high TOC oil shale formation predicted by the traditional prediction method and the method of the present invention. As shown in Table 1, the pressure coefficient of the second section of the deeply buried oil shale in Well W8 is relatively high, which is 1.78. During the analysis while drilling and after drilling, it was found that the error between the predicted pressure before drilling and the measured pressure coefficient was small, only -0.56%. Compared with the error of 10.2% caused by the traditional method, the accuracy of the present invention is very high.

[0105] The drilling test results of W5, W6 and W8 wells proved the effectiveness and practicability of the present invention, laid a technical foundation for the pressure prediction of subsequent oil shale exploration wells and development wells in the area, and provided technical support for the reasonable wellbore structure design and improved drilling safety in the oil shale exploration and development in the western South China Sea oilfield.

[0106] Embodiment 4

[0107] Figure 6 A system structure diagram for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization according to an embodiment of the present invention. Figure 6 As shown, according to one embodiment of the present invention, a system for calculating the contribution rate of hydrocarbon generation and pressurization of high TOC oil shale includes:

[0108] TOC content calculation module, used to calculate the TOC content of oil shale;

[0109] The velocity relationship building module is used to conduct intersection analysis of P-wave velocity and S-wave velocity for mudstone and immature oil shale in the same layer in the same area, and establish the target P-wave and S-wave velocity relationship;

[0110] The P-wave velocity reconstruction module is used to reconstruct the P-wave velocity of high TOC oil shale based on the target P-wave and S-wave velocity relationship to obtain the reconstructed P-wave velocity;

[0111] The hydrocarbon generation pressurization contribution rate calculation module is used to build a basic model for pressure prediction, and calculate the pore pressure background pressure of high TOC oil shale due to undercompaction based on the basic model for pressure prediction and reconstructed longitudinal wave velocity;

[0112] The pressure coefficient difference of hydrocarbon generation pressurization is obtained based on the pore pressure background pressure, and the velocity difference between the measured acoustic wave velocity and the reconstructed longitudinal wave velocity is obtained; the velocity difference and the pressure coefficient difference are intersected and analyzed to obtain the target fitting formula, and the contribution of hydrocarbon generation pressurization is calculated based on the fitting formula.

[0113] According to one embodiment of the present invention, an electronic device includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, any one of the methods of the present invention for calculating the pressurization contribution rate of hydrocarbon generation in high TOC oil shale is implemented.

[0114] According to one embodiment of the present invention, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, any method of calculating the pressurization contribution rate of high TOC oil shale hydrocarbon generation is implemented in the present invention.

[0115] According to one embodiment of the present invention, a computer program product includes a computer program, which, when executed by a processor, implements the steps of any method of calculating the pressurization contribution rate of hydrocarbon generation in high TOC oil shale according to the present invention.

[0116] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems, devices, media and computer program products can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0117] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

[0118] It should be understood that the size of the serial numbers of each step in the content of the invention and the embodiments of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Claims

1. A method for calculating the contribution rate of hydrocarbon generation and pressurization of high TOC oil shale, characterized in that: The following steps are involved: Calculate the TOC content of oil shale; Conduct intersection analysis of P-wave velocity and S-wave velocity for mudstone and immature oil shale in the same region and the same formation, and establish the target P-wave and S-wave velocity relationship. Based on the target P-wave and S-wave velocity relationship, the P-wave velocity of the high TOC oil shale is reconstructed to obtain a reconstructed P-wave velocity; Constructing a basic model for pressure prediction, and calculating the pore pressure background pressure of the high TOC oil shale due to undercompaction based on the basic model for pressure prediction and the reconstructed P-wave velocity; Obtaining a hydrocarbon generation boost pressure coefficient difference based on the pore pressure background pressure, and obtaining a velocity difference between the measured acoustic wave velocity and the reconstructed longitudinal wave velocity; The velocity difference and the pressure coefficient difference are subjected to intersection analysis to obtain a target fitting formula, and the contribution of hydrocarbon generation pressure increase is calculated based on the fitting formula.

2. The method for calculating the pressurization contribution rate of high TOC oil shale hydrocarbon generation according to claim 1, characterized in that: Calculating the TOC content of oil shale includes: calculating the TOC content of oil shale based on acoustic wave and resistivity logging data combined with geochemical analysis, specifically including the following steps: Acquire acoustic transit time and resistivity data through logging while drilling or Grand Slam technology; The acoustic time difference curve and resistivity curve are displayed in reverse scale and superimposed; Calculate the estimated value of TOC content based on the acoustic time difference and the offset amplitude of resistivity relative to their respective base value lines; The TOC content estimate is calibrated using TOC data obtained from geochemical analysis.

3. The method for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization according to claim 1, characterized in that: The target longitudinal and transverse wave velocity relationship is: Vp=1.33078*Vs+1154 Among them, Vp is the longitudinal wave velocity and Vs is the shear wave velocity.

4. The method for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization according to claim 1, characterized in that: Construct a basic model for pressure prediction, including: Analyze the acoustic logging data of rocks at different depths in the target sedimentary basin to obtain the compaction trend of rock velocity with depth in the area; The pressure prediction basic model is constructed based on the relationship between the target velocity difference and the pressure coefficient of the target sedimentary basin and the compaction trend.

5. The method for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization according to claim 1, characterized in that: Obtaining the hydrocarbon generation boost pressure coefficient difference, including: Based on the reconstructed P-wave velocity, a pore pressure background value is calculated without the effect of hydrocarbon generation pressurization to obtain a reconstructed pore pressure background pressure; The actual measured pore pressure is subtracted from the reconstructed pore pressure background pressure to obtain the hydrocarbon generation pressurization pressure coefficient difference.

6. A system for calculating the contribution rate of hydrocarbon generation and pressurization of high TOC oil shale, characterized in that: include: TOC content calculation module, used to calculate the TOC content of oil shale; The velocity relationship building module is used to conduct intersection analysis of P-wave velocity and S-wave velocity for mudstone and immature oil shale in the same layer in the same area, and establish the target P-wave and S-wave velocity relationship; A longitudinal wave velocity reconstruction module is used to reconstruct the longitudinal wave velocity of the high TOC oil shale based on the target longitudinal and transverse wave velocity relationship to obtain a reconstructed longitudinal wave velocity; A hydrocarbon generation pressurization contribution rate calculation module is used to construct a pressure prediction basic model, and calculate the pore pressure background pressure of the high TOC oil shale due to undercompaction based on the pressure prediction basic model and the reconstructed longitudinal wave velocity; Obtaining a hydrocarbon generation boost pressure coefficient difference based on the pore pressure background pressure, and obtaining a velocity difference between the measured acoustic wave velocity and the reconstructed longitudinal wave velocity; The velocity difference and the pressure coefficient difference are subjected to intersection analysis to obtain a target fitting formula, and the contribution of hydrocarbon generation pressure increase is calculated based on the fitting formula.

7. The system for calculating the contribution rate of high TOC oil shale to hydrocarbon generation and pressurization according to claim 6, characterized in that: The target longitudinal and transverse wave velocity relationship is: Vp=1.33078*Vs+1154 Among them, Vp is the longitudinal wave velocity and Vs is the shear wave velocity.

8. An electronic device, characterized in that: The method comprises a processor, a memory and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, the method for calculating the pressurization contribution rate of hydrocarbon generation of high TOC oil shale is implemented as described in any one of claims 1 to 5.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for calculating the pressurization contribution rate of high TOC oil shale hydrocarbon generation is implemented as described in any one of claims 1-5.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method for calculating the pressurization contribution rate of high TOC oil shale hydrocarbon generation are implemented as described in any one of claims 1 to 5.

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