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

Abstract

The present application relates to the technical field of oil exploitation, in particular to a method and system for calculating the contribution rate of hydrocarbon generation pressure increase of high TOC oil shale, which comprises the following steps: calculating the TOC content of oil shale; establishing a target P-wave and S-wave velocity relationship formula; reconstructing the P-wave velocity of high TOC oil shale based on the target P-wave and S-wave velocity relationship formula to obtain the reconstructed P-wave velocity; constructing a pressure prediction basic model, calculating the pore pressure background pressure of the undercompaction cause of high TOC oil shale based on the pressure prediction basic model and the reconstructed P-wave velocity; obtaining the pressure coefficient difference of hydrocarbon generation pressure increase based on the pore pressure background pressure, and obtaining the velocity difference between the measured acoustic wave velocity and the reconstructed P-wave velocity; performing cross analysis on the velocity difference and the pressure coefficient difference to obtain a target fitting formula, and calculating the contribution amount of hydrocarbon generation pressure increase based on the fitting formula. The present application realizes the quantitative calculation of the contribution amount of hydrocarbon generation pressure increase of high TOC oil shale and the high-precision prediction of the formation pore pressure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil exploitation, in particular to a method and system for calculating the contribution rate of high TOC oil shale hydrocarbon generation pressure increase. BACKGROUND

[0002] The Beibuwan Basin, located in the South China Sea, is a proven hydrocarbon-rich sag, which is a Cenozoic sedimentary basin with rapid subsidence. The development of abnormal high pressure in the second member of Liushagang Formation in the middle-deep layer is one of its important characteristics. Previous studies generally believe that this abnormal high pressure is mainly generated by the thick under-compacted mudstone formed by rapid deposition, and the weak tectonic activity in the later period plays an important role in maintaining this abnormal high pressure. For clastic rock strata, the traditional mudstone under-compaction model shows relatively high accuracy in pressure prediction. However, with the continuous expansion of exploration and the gradual increase of exploration strata, especially in the past two years, the development of oil shale exploration drilling, it is found that in addition to under-compaction, the oil shale in the second member of Liushagang Formation in Weixinan Sag also has a non-under-compaction abnormal pressure cause. When relying solely on the mudstone under-compaction model for pre-drilling pressure prediction, there is a large error between the predicted pressure of the oil shale formation and the measured formation pressure, which poses a new challenge to pressure prediction in the shale oil field. For Weixinan Sag, the study of oil shale abnormal pressure is a new field. In order to meet this challenge, researchers first use the velocity-density crossplot method to determine the cause of abnormal pressure; secondly, use acoustic curve reconstruction to calculate the proportion of under-compaction caused pressure in total pressure; finally, combined with the actual pressure measurement point, a shale oil hydrocarbon generation pressure contribution template is established. This research method has been successfully applied in pre-drilling pressure prediction and while-drilling pressure analysis of new wells in Weixinan Sag, and has shown high accuracy, providing technical support for shale oil discovery and technical support for reasonable well structure design and improving drilling safety.

[0003] However, some problems still occur in actual drilling. For example, when drilling the first shale oil parameter well W1 in the South China Sea, although the pre-drilling pressure prediction showed high accuracy in the upper sequence and above the second member of Liufang Formation, complex well conditions appeared in the lower sequence oil shale section of the second member of Liufang Formation, and the integrated well condition judgment showed that the formation pressure coefficient was significantly higher than the pre-drilling predicted pressure, and the formation pressure prediction had a large deviation. The same situation also occurred in the subsequent drilling of W4 well. This shows that for the lower sequence oil shale section of the second member of Liufang Formation, there is a large error in pressure calculation according to the mudstone under-compaction model, and there is also a certain contradiction in the mechanism of abnormal pressure cause. In addition, the pore pressure and fracture pressure drilling operation window of this section of oil shale formation is very narrow, and the accuracy requirement of pressure prediction is extremely high.

[0004] Therefore, in view of the above problems, it is necessary to carry out research on the cause judgment and prediction method of abnormal pressure of oil shale formation, aiming to form a set of technical system to provide technical support for subsequent oil shale drilling. However, the current research still cannot accurately calculate the contribution of high TOC (total organic carbon) oil shale hydrocarbon generation pressure, which leads to a large error in the predicted pressure of high TOC oil shale. Therefore, further optimization and improvement of the prediction method of abnormal pressure of oil shale formation is still the focus of current research. SUMMARY

[0005] The purpose of the present application is to provide a method and system for calculating the contribution rate of high TOC oil shale hydrocarbon generation pressure.

[0006] The present application achieves the above-mentioned purpose by the following technical solutions:

[0007] A method for calculating the contribution rate of high TOC oil shale hydrocarbon generation pressure, comprising the following steps:

[0008] Calculating the TOC content of oil shale;

[0009] Crossplot analysis of P-wave velocity and S-wave velocity of mudstone and immature oil shale in the same region and the same layer is carried out, and a target P-wave and S-wave velocity relationship is established;

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

[0011] A pressure prediction base model is constructed, and the pore pressure background pressure of high TOC oil shale caused by undercompaction is calculated based on the pressure prediction base model and the reconstructed P-wave velocity;

[0012] Based on the pore pressure background pressure, the pressure coefficient difference of hydrocarbon generation is obtained, and the velocity difference between the measured acoustic velocity and the reconstructed P-wave velocity is obtained; the velocity difference and the pressure coefficient difference are crossplot analyzed to obtain a target fitting formula, and the contribution of hydrocarbon generation pressure is calculated based on the fitting formula.

[0013] Further, the TOC content of oil shale is calculated, including: calculating the TOC content of oil shale according to acoustic and resistivity logging data combined with geochemical analysis, specifically including the following steps,

[0014] Acoustic travel time and resistivity data are obtained by drilling or big jackpot logging technology;

[0015] The acoustic travel time curve and the resistivity curve are displayed in reverse scale superposition;

[0016] According to the offset amplitude of acoustic travel time and resistivity relative to their respective base lines, the TOC content estimate value is calculated;

[0017] The TOC content estimated value is calibrated by using TOC data obtained by geochemical analysis.

[0018] Further, the target P-wave and S-wave velocity relationship is:

[0019] Vp = 1.33078 * Vs + 1154

[0020] Wherein, Vp is P-wave velocity, and Vs is S-wave velocity.

[0021] Further, a pressure prediction base model is constructed, including:

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

[0023] Based on the relationship between the target velocity difference of the target sedimentary basin and the pressure coefficient, and the compaction trend, the pressure prediction base model is constructed.

[0024] Further, the hydrocarbon generation pressure coefficient difference is obtained, including:

[0025] Based on the reconstructed P-wave velocity, the pore pressure background value without the hydrocarbon generation pressure effect is calculated, and the reconstructed pore pressure background pressure is obtained.

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

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

[0028] A TOC content calculation module for calculating the TOC content of oil shale;

[0029] A velocity relationship construction module for cross-plot analysis of P-wave velocity and S-wave velocity of mudstone and immature oil shale in the same layer system in the same region, and establishing a target P-wave and S-wave velocity relationship;

[0030] A P-wave velocity reconstruction module for reconstructing the P-wave velocity of high TOC oil shale based on the target P-wave and S-wave velocity relationship to obtain a reconstructed P-wave velocity;

[0031] The hydrocarbon generation pressure contribution rate calculation module is configured to construct a pressure prediction base model, calculate a high TOC oil shale undercompaction caused pore pressure background pressure based on the pressure prediction base model and the reconstructed P-wave velocity, obtain a pressure coefficient difference of the hydrocarbon generation pressure based on the pore pressure background pressure, obtain a velocity difference between a measured S-wave velocity and the reconstructed P-wave velocity, obtain a target fitting formula through crossplot analysis of the velocity difference and the pressure coefficient difference, and calculate a contribution amount of the hydrocarbon generation pressure based on the fitting formula.

[0032] Further, the target P-S wave velocity relationship is:

[0033] Vp=1.33078*Vs+1154

[0034] wherein Vp is the P-wave velocity and Vs is the S-wave velocity.

[0035] An electronic device includes a processor, a memory, and a computer program stored on the memory and executable on the processor, and the computer program, when executed by the processor, implements the method for calculating the hydrocarbon generation pressure contribution rate of high TOC oil shale according to any one of the above.

[0036] A computer readable storage medium stores a computer program, and the computer program, when executed by a processor, implements the method for calculating the hydrocarbon generation pressure contribution rate of high TOC oil shale according to any one of the above.

[0037] A computer program product includes a computer program, and the computer program, when executed by a processor, implements the steps of the method for calculating the hydrocarbon generation pressure contribution rate of high TOC oil shale according to any one of the above.

[0038] The present application provides an innovative solution to the problem that the pressure prediction method in the prior art cannot accurately predict and calculate the contribution amount of the hydrocarbon generation pressure of high TOC oil shale, and the predicted pressure has a large error.

[0039] Firstly, the present application can realize real-time prediction before drilling and during drilling. This feature enables immediate data acquisition and analysis during drilling operations, allowing timely adjustment of drilling strategies to improve drilling efficiency and safety.

[0040] Secondly, the present application can accurately determine the abnormal pressure causes of mudstone, immature oil shale and high TOC oil shale. Through detailed analysis of the pressure causes of different rock types, the present application provides more accurate geological information for geological exploration and oil and gas resource development.

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

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

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

[0044] Figure 1 Flow chart of the method for calculating the hydrocarbon generation pressure contribution rate of high TOC oil shale according to an embodiment of the present application;

[0045] Figure 2 Flow chart of the method for calculating the hydrocarbon generation pressure contribution rate of high TOC oil shale according to another embodiment of the present application;

[0046] Figure 3 Schematic diagram of obtaining the reconstructed P-wave velocity according to an embodiment of the present application;

[0047] Figure 4 Schematic diagram of the pressure prediction base model according to an embodiment of the present application;

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

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

[0050] The present application will now be discussed with reference to exemplary embodiments. It should be understood that the discussed embodiments are only to enable those of ordinary skill in the art to better understand and thus implement the content of the present application, and are not intended to imply any limitation on the scope of the present application.

[0051] As used herein, the term "comprising" and variations thereof are to be construed as meaning "including but not limited to". The term "based on" is to be construed as "based at least in part on". The terms "one embodiment" and "an embodiment" are to be construed as "at least one embodiment".

[0052] Embodiment one

[0053] Figure 1 Flow chart of the method for calculating the contribution rate of high TOC oil shale hydrocarbon generation pressure in an embodiment of the present application; Figure 3 Schematic diagram for obtaining reconstructed P-wave velocity in an embodiment of the present application; Figure 4 Schematic diagram of a pressure prediction base model in an embodiment of the present application; Figure 5 Schematic diagram for calculating the contribution amount of hydrocarbon generation pressure based on a fitting formula. As shown in FIG. 5, according to an embodiment of the present application, a method for calculating the contribution rate of high TOC oil shale hydrocarbon generation pressure comprises the following steps: Figure 1 、 3 -5 shows a method for calculating the contribution rate of high TOC oil shale hydrocarbon generation pressure, comprising 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 not only helps us evaluate the oil storage potential of oil shale, but also provides important basis for subsequent exploitation and utilization.

[0056] Step S104: Crossplot analysis of P-wave velocity and S-wave velocity of mudstone and immature oil shale in the same region and the same layer system to establish the target P-S wave velocity relationship.

[0057] Through crossplot analysis of P-wave velocity and S-wave velocity of mudstone and oil shale in the same region and the same layer system, it is found that immature oil shale, due to the influence of hydrocarbon fluids, has the same trend and rule of P-S wave change distribution as mudstone on the crossplot, and the target P-S wave velocity relationship can be established through the P-S wave data of mudstone and immature oil shale in the area.

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

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

[0060] Due to the contribution of hydrocarbon generation pressurization, the measured P-wave velocity and density of high TOC oil shale are often low due to the presence of hydrocarbon substances in the fluid, which is significantly different from the acoustic logging data of conventional mudstone and immature hydrocarbon source rock. In the crossplot, the data points of high TOC oil shale will usually fall below the loading curve of mudstone and immature hydrocarbon 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 the P-wave mainly propagates along the rock skeleton, and the presence of hydrocarbon fluid weakens the elastic modulus of the rock skeleton. Unlike P-wave, the effect of hydrocarbon fluid on the S-wave velocity of high TOC oil shale is relatively small. S-wave mainly propagates along the shear direction of the rock, and is less affected by the fluid. In order to eliminate the effect of hydrocarbon fluid on the P-wave velocity in high TOC oil shale, for high TOC oil shale, we use its S-wave velocity data to reconstruct the reconstructed P-wave velocity that is not affected by hydrocarbon fluid according to the established target P-S wave velocity relationship. The reconstructed P-wave velocity is closer to the true velocity of the rock skeleton, and can more accurately reflect the physical properties of the rock.

[0061] Step S108: Construct a pressure prediction base model, and calculate the pore pressure background pressure of high TOC oil shale caused by undercompaction based on the pressure prediction base model and the reconstructed P-wave velocity.

[0062] Using the reconstructed P-wave velocity, combined with the compaction trend of velocity with depth and the relationship between velocity difference and pressure coefficient in Weixinan Sag, a pressure prediction base model is constructed, and the pore pressure background pressure of high TOC oil shale caused by undercompaction is calculated. Through the pressure prediction base model, we can calculate the pore pressure of high TOC oil shale at different depths. The part caused by undercompaction in these pore pressures is the pore pressure background pressure caused by undercompaction. Undercompaction refers to the fact that during the compaction process of the rock, due to some reasons (such as the presence of hydrocarbon fluid, the particularity of the rock skeleton, etc.), the rock fails to achieve normal compaction, resulting in the preservation of pore space and the formation of higher pore pressure. In the calculated pore pressure, removing the part caused by other factors (such as tectonic stress, fluid expansion, etc.) can obtain the pore pressure background pressure caused by undercompaction.

[0063] Step S110: Obtain the pressure coefficient difference of hydrocarbon generation pressurization based on the pore pressure background pressure, and obtain the velocity difference between the measured acoustic velocity and the reconstructed P-wave velocity;

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

[0065] In the embodiment, the velocity difference between the measured acoustic wave velocity and the reconstructed P-wave velocity of the high TOC oil shale section is calculated, and the velocity difference represents the velocity contribution of the high TOC oil shale hydrocarbon generation pressurization part. The actual measured pressure data of the drilled well is subtracted from the reconstructed P-wave velocity to calculate the undercompaction porosity pressure background pressure of the high TOC oil shale, and the difference of the hydrocarbon generation pressurization pressure coefficient is obtained. Through regression analysis and other methods, a fitting formula between the velocity difference and the pressure coefficient difference can be derived. The formula can be used to quantify the influence of hydrocarbon generation pressurization on the acoustic wave velocity and the pore pressure. Using the fitting formula, the specific contribution of the hydrocarbon generation pressurization in the high TOC oil shale can be calculated according to the measured velocity difference or pressure coefficient difference.

[0066] The present application reconstructs the P-wave velocity of the high TOC oil shale, combines with the pressure prediction model, realizes the quantitative calculation of the hydrocarbon generation pressurization contribution of the high TOC oil shale and the high-precision prediction of the formation pore pressure, breaks through the limitation of the traditional prediction method, enhances the adaptability of the oil shale target, and realizes the real-time prediction in the pre-drilling and drilling process.

[0067] According to an embodiment of the present application, step S102 comprises: calculating the TOC content of oil shale according to acoustic wave and resistivity logging data combined with geochemical analysis, specifically comprising the following steps,

[0068] Step S1022, acquiring acoustic travel time and resistivity data through while-drilling or full-bore logging technology;

[0069] Step S1024, reverse scaling and superimposed display of the acoustic travel time curve and the resistivity curve;

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

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

[0072] In the embodiment, the TOC content of oil shale is calculated by data acquisition, curve superposition, TOC value calculation and geochemical analysis calibration, specifically including: first, acoustic travel time curve and resistivity curve data are acquired by while-drilling or big jackpot logging technology. These data reflect the physical properties of rock, including porosity, permeability and electrical conductivity, etc. Then, the acoustic travel time curve and the resistivity curve are reversely scaled and superimposed. In the rock lacking of organic matter (i.e. no TOC or low TOC), the two curves are well superimposed due to the relatively uniform physical properties of the rock. In the high TOC oil shale rich in organic matter, the physical properties of the rock are changed due to the existence of organic matter, resulting in poor superimposition of the two curves and difference. Then, according to the offset amplitude of the acoustic travel time and the resistivity relative to the respective base lines, the TOC value, i.e. the TOC content estimation value, can be calculated. The base line represents the reference value of the physical properties of the rock in the region. Finally, the TOC data obtained by geochemical analysis is used to calibrate the previous calculation result. Geochemical analysis is the most direct and accurate method to determine the content of organic matter in rock, but compared with logging method, it has higher cost and longer time consumption. Therefore, the TOC value is quickly calculated by logging method, and is calibrated by combining with geochemical analysis, so that the work efficiency and accuracy can be greatly improved.

[0073] The present application acquires acoustic travel time and resistivity data by while-drilling or big jackpot logging technology, calculates the TOC content estimation value of oil shale by using the reverse scale superimposition display of the two curves and the offset amplitude relative to the base line, and calibrates by geochemical analysis, so that efficient and accurate calculation of the TOC content of oil shale is realized, and the cost is reduced and the work efficiency is improved.

[0074] According to one embodiment of the present application, in step S104, the target P-wave and S-wave velocity relationship is:

[0075] Vp = 1.33078 * Vs + 1154

[0076] wherein Vp is the P-wave velocity and Vs is the S-wave velocity.

[0077] Crossplot analysis is a method of graphically displaying the relationship between two variables. By plotting scatter plots or trend lines, one can visually observe the changing trend and correlation between variables. In this embodiment, the P-wave velocity and S-wave velocity are used as two variables for crossplot analysis of mudstone and immature oil shale. Mudstone is a common sedimentary rock with relatively stable physical properties. There is a certain relationship between P-wave velocity and S-wave velocity. In the crossplot, the P-S velocity points of mudstone show a certain distribution trend, which reflects the uniformity and stability of the internal structure of mudstone. Immature oil shale, which has not undergone the generation and migration of hydrocarbon fluids, has similar physical properties to mudstone but contains a certain amount of organic matter. In the crossplot, the P-S velocity points of immature oil shale are consistent with the distribution trend of mudstone, indicating that they have certain similarities in physical properties. By crossplot analysis of mudstone and immature oil shale in the same region and the same layer, we found that the P-S velocity distribution trend of the two in the crossplot is the same. Therefore, we can use this characteristic to establish the target P-S velocity relationship by fitting the P-S data of mudstone and immature oil shale.

[0078] The present application crossplots the P-wave velocity and S-wave velocity of mudstone and immature oil shale, uses the consistency of their distribution trend in the crossplot, successfully fits the data to establish the target P-S velocity relationship, and effectively reveals the similarity of the two rocks in physical properties, providing a powerful tool for related geological analysis.

[0079] According to an embodiment of the present application, 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: Based on the relationship between the target velocity difference and the pressure coefficient of the target sedimentary basin, the compaction trend, a pressure prediction base model is constructed.

[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., providing an important basis for subsequent analysis. Then, a pressure prediction base model is constructed according to the compaction trend of the velocity with depth in Weixinan Sag (target sedimentary basin). Weixinan Sag is a region with complex geological conditions, and its velocity field is affected by multiple factors. By studying the compaction trend of the velocity with depth in this region, a pressure prediction model reflecting the geological characteristics of the region can be established. This model will serve as an important tool for subsequent calculation of the background pressure of the pore pressure. Then, the relationship between the velocity difference and the pressure coefficient is used to further improve the pressure prediction model. The velocity difference refers to the difference between the actually measured P-wave velocity and the P-wave velocity under normal compaction trend, which reflects the compaction state of the rock and the change of the pore pressure. The pressure coefficient is a parameter reflecting the relationship between the pore pressure and the hydrostatic pressure. By combining the velocity difference and the pressure coefficient, a background pressure model that can more accurately predict the pore pressure can be established. Finally, the constructed pressure prediction base model is used to calculate the pore pressure background pressure of the high TOC oil shale undercompaction.

[0083] The present application can accurately predict the pore pressure background pressure of the high TOC oil shale undercompaction by analyzing the acoustic logging data of the rock in the target sedimentary basin, constructing a pressure prediction base model, and improving the model using the relationship between the target velocity difference and the pressure coefficient, thereby providing an important basis for geological exploration and development.

[0084] According to an embodiment of the present application, in step S110, the hydrocarbon generation pressurization pressure coefficient difference is obtained, including:

[0085] Step one, based on the reconstructed P-wave velocity, the pore pressure background value under the action of no hydrocarbon generation pressurization is calculated, and the reconstructed pore pressure background pressure is obtained.

[0086] Step two, the difference between the actually measured pore pressure and the reconstructed pore pressure background pressure is obtained, and the hydrocarbon generation pressurization pressure coefficient difference is obtained.

[0087] In this embodiment, through pressure measurement during drilling, we can obtain the actual pore pressure data of the high TOC oil shale section. Based on the reconstructed P-wave velocity and the known rock physical relationship, we can calculate the pore pressure background value under the action of no hydrocarbon generation pressurization. The difference between the actually measured pore pressure and the reconstructed pore pressure background value is obtained, and the hydrocarbon generation pressurization pressure coefficient difference value is obtained. This difference reflects the actual contribution of hydrocarbon generation pressurization to the pore pressure.

[0088] The present application accurately obtains the hydrocarbon generation pressurization pressure coefficient difference by calculating the pore pressure background value under the reconstructed P-wave velocity and subtracting the actually measured pore pressure, realizes the quantitative evaluation of the contribution of the hydrocarbon generation pressurization to the pore pressure, and further improves the accuracy of the pore pressure prediction of the high TOC oil shale formation.

[0089] Embodiment two

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

[0091] Step S202: Calculate the TOC content of the oil shale according to the acoustic wave and resistivity logging data combined with the geochemical analysis, use the while-drilling or the big full-court acoustic wave and resistivity curves, and superimpose and display the two curves in reverse scale, the superimposition of the two curves is better in the rock lacking organic matter (without TOC or low TOC), and the superimposition of the two curves is poor in the high TOC oil shale rich in organic matter, there is a difference, calculate the value of TOC according to the amplitude of the acoustic wave time difference and the resistivity offset from the respective base value line, and calibrate the calculation result with the TOC of the geochemical analysis;

[0092] Step S204: Through the crossplot analysis of the P-wave velocity and the S-wave velocity of the mudstone and the oil shale in the same layer system in the same area, it is found that the immature oil shale has the same change trend and rule as the mudstone on the crossplot due to the influence of no hydrocarbon fluid, the P-wave and S-wave data of the mudstone and the immature oil shale in the area can be used to fit and establish the P-wave and S-wave velocity relationship, and the specific formula is,

[0093] Vp=1.33078*Vs+1154

[0094] Wherein, Vp is the P-wave velocity, and Vs is the S-wave velocity.

[0095] Step S206: Since the oil shale skeleton contains TOC (total organic carbon, the same below) and has the contribution of the hydrocarbon generation pressurization, the high TOC oil shale has the measured velocity density lower due to the existence of the hydrocarbon in the fluid, and the whole deviates from the loading curve of the mudstone and the immature source rock and falls below the loading curve, the existence of the hydrocarbon fluid reduces the P-wave velocity of the oil shale, but has little influence on the S-wave velocity of the oil shale, so in order to eliminate the influence of the hydrocarbon fluid in the high TOC oil shale on the P-wave velocity, the S-wave velocity of the high TOC oil shale is reconstructed into the P-wave velocity according to the P-wave and S-wave velocity relationship fitted by the mudstone and the low TOC oil shale in step S204;

[0096] Step S208: using the high TOC oil shale P-wave velocity reconstructed in step S206, calculating the pore pressure background pressure of the high TOC oil shale undercompaction genesis according to the compaction trend of the velocity changing with depth in Weixinan sag and the pressure prediction basic model constructed by the velocity difference and the pressure coefficient;

[0097] wherein the pressure prediction basic model is the corresponding relationship of 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 genesis in the basin, the pressure coefficient of the basin edge is higher than that of the basin center under the same velocity difference of the undercompaction genesis and the basin center compared with the basin edge, and the pressure coefficient of the model with non-undercompaction genesis is obviously higher than that of the undercompaction genesis under the same velocity difference.

[0098] Step S210: calculating the velocity difference between the measured acoustic velocity and the reconstructed P-wave velocity of the high TOC oil shale section, which represents the velocity contribution of the high TOC oil shale hydrocarbon generation and pressure increase part, and then subtracting the pore pressure background pressure of the high TOC oil shale undercompaction genesis calculated by the actual measured pressure data and the reconstructed P-wave velocity from the actual measured pressure data to obtain the difference of the hydrocarbon generation and pressure increase pressure coefficient, and then cross analyzing and fitting the formula of the velocity difference and the pressure coefficient difference to calculate the contribution of the hydrocarbon generation and pressure increase.

[0099] The present application can realize the real-time prediction during drilling before drilling and while drilling, can realize the abnormal pressure genesis judgment of mudstone, immature oil shale and high TOC oil shale, and can realize the quantitative calculation and prediction of the high TOC oil shale hydrocarbon generation and pressure increase contribution, and is suitable for oil shale targets. The present application breaks through the traditional mudstone undercompaction abnormal pressure genesis and prediction method, and realizes the high-precision formation pore pressure prediction of high TOC oil shale.

[0100] Example three

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

[0102]

[0103] Table 1: data comparison table of predicting the formation pressure coefficient of high TOC oil shale by the traditional prediction method and the method of the present application

[0104] Table 1 is a data comparison table of predicting the pressure coefficient of high TOC oil shale formation by using the traditional prediction method and the method of the present application, as shown in Table 1, the pressure coefficient of the oil shale of the second member of the W8 well buried deep is high, which is 1.78, and when drilling and post-drilling analysis, it is found that the error between the predicted pressure before drilling and the measured pressure coefficient is small, which is only-0.56%, compared with the error of 10.2% generated by the traditional method, the precision of the present application is very high.

[0105] The drilling test results of the W5, W6 and W8 wells prove the effectiveness and practicability of the present application, lay a technical foundation for the pressure prediction of subsequent oil shale exploration wells and development wells in the area, and provide technical support for the reasonable well structure design and the improvement of drilling safety for oil shale exploration and development in the western oilfield of the South China Sea.

[0106] Example Four

[0107] Figure 6 The system structure diagram for calculating the hydrocarbon generation pressure contribution rate of high TOC oil shale according to an embodiment of the present application is shown in Figure 1. Figure 6 As shown in Figure 1, according to an embodiment of the present application, a system for calculating the hydrocarbon generation pressure contribution rate of high TOC oil shale comprises:

[0108] a TOC content calculation module for calculating the TOC content of oil shale;

[0109] a velocity relationship construction module for crossplot analysis of the P-wave velocity and the S-wave velocity of the mudstone and the immature oil shale of the same layer system in the same area, and establishing a target P-wave and S-wave velocity relationship;

[0110] a P-wave velocity reconstruction module for reconstructing the P-wave velocity of the high TOC oil shale based on the target P-wave and S-wave velocity relationship, and obtaining the reconstructed P-wave velocity;

[0111] a hydrocarbon generation pressure contribution rate calculation module for constructing a pressure prediction base model, and calculating the pore pressure background pressure of the undercompaction cause of the high TOC oil shale based on the pressure prediction base model and the reconstructed P-wave velocity;

[0112] based on the pore pressure background pressure, obtaining the pressure coefficient difference of the hydrocarbon generation pressure, obtaining the velocity difference between the measured acoustic velocity and the reconstructed P-wave velocity; crossplot analyzing the velocity difference and the pressure coefficient difference to obtain a target fitting formula, and calculating the contribution amount of the hydrocarbon generation pressure based on the fitting formula.

[0113] According to an embodiment of the present application, an electronic device comprises a processor, a memory and a computer program stored on the memory and executable on the processor, and the computer program is executed by the processor to implement any method for calculating the hydrocarbon generation pressure contribution rate of high TOC oil shale.

[0114] According to an embodiment of the present application, a computer readable storage medium, a computer program is stored on the computer readable storage medium, the computer program is executed by a processor to implement any of the methods for calculating the high TOC oil shale hydrocarbon generation pressure contribution rate.

[0115] According to an embodiment of the present application, a computer program product comprises a computer program, the computer program is executed by a processor to implement any of the steps of the methods for calculating the high TOC oil shale hydrocarbon generation pressure contribution rate.

[0116] Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working processes of the above-described system, device, medium and computer program product can refer to the corresponding processes in the foregoing method embodiments, which will not be described here.

[0117] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the application involved in the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and 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 can be replaced with the technical features disclosed in the present application (but not limited to) having similar functions to form technical solutions.

[0118] It should be understood that the sequence of the steps in the summary of the application and the embodiments does not absolutely mean the order of execution, the execution order of the processes should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

Claims

1. A method of calculating the high TOC oil shale hydrocarbon generation pressurization contribution rate, characterized in that, The method comprises the following steps: calculating oil shale TOC content; crossplotting the P-wave velocity and the S-wave velocity of the mudstone and the immature oil shale in the same layer system in the same area to establish a target P-wave and S-wave velocity relationship; reconstructing the P-wave velocity of the high TOC oil shale based on the target P-wave and S-wave velocity relationship to obtain a reconstructed P-wave velocity; constructing a pressure prediction base model, and calculating the pore pressure background pressure of the high TOC oil shale caused by undercompaction based on the pressure prediction base model and the reconstructed P-wave velocity; obtaining a hydrocarbon generation pressure coefficient difference based on the pore pressure background pressure, and obtaining a velocity difference between the measured acoustic velocity and the reconstructed P-wave velocity; crossplotting the velocity difference and the pressure coefficient difference to obtain a target fitting formula, and calculating the contribution of the hydrocarbon generation pressure based on the fitting formula; wherein the target P-wave and S-wave velocity relationship is: ， wherein, Vp is the longitudinal wave velocity, Vp is the longitudinal wave velocity, The pressure prediction base model is constructed, comprising: analyzing acoustic logging data of rocks at different depths in a target sedimentary basin to obtain a compaction trend of rock velocity with respect to depth in the area; constructing the pressure prediction base model based on the relationship between the target velocity difference and the pressure coefficient of the target sedimentary basin and the compaction trend; The hydrocarbon generation pressure coefficient difference is obtained, comprising: calculating a pore pressure background value without the effect of hydrocarbon generation pressure based on the reconstructed P-wave velocity to obtain a reconstructed pore pressure background pressure; obtaining the hydrocarbon generation pressure coefficient difference by subtracting the actual measured pore pressure from the reconstructed pore pressure background pressure.

2. The method of claim 1, wherein, The method for calculating the TOC content of oil shale comprises the following steps: obtaining acoustic travel time and resistivity data through while-drilling or full-bore logging technology; superimposing and displaying the acoustic travel time curve and the resistivity curve in reverse scale; calculating the TOC content estimate value according to the offset amplitude of the acoustic travel time and the resistivity with respect to their respective base lines; calibrating the TOC content estimate value by using the TOC data obtained through geochemical analysis.

3. A system for calculating the high TOC oil shale hydrocarbon generation pressurization contribution rate, characterized in that, The method comprises: a TOC content calculation module for calculating the TOC content of oil shale; a velocity relationship construction module for crossplotting the P-wave velocity and the S-wave velocity of the mudstone and the immature oil shale in the same layer system in the same area to establish a target P-wave and S-wave velocity relationship; a P-wave velocity reconstruction module for reconstructing the P-wave velocity of the high TOC oil shale based on the target P-wave and S-wave velocity relationship to obtain a reconstructed P-wave velocity; a hydrocarbon generation pressure contribution rate calculation module for constructing a pressure prediction base model, and calculating the pore pressure background pressure of the high TOC oil shale caused by undercompaction based on the pressure prediction base model and the reconstructed P-wave velocity; obtaining a hydrocarbon generation pressure coefficient difference based on the pore pressure background pressure, and obtaining a velocity difference between the measured acoustic velocity and the reconstructed P-wave velocity; crossplotting the velocity difference and the pressure coefficient difference to obtain a target fitting formula, and calculating the contribution of the hydrocarbon generation pressure based on the fitting formula; wherein the target P-wave and S-wave velocity relationship is: ， wherein, Vp is the longitudinal wave velocity, Vt is the transverse wave velocity; The pressure prediction base model is constructed, comprising: Analyzing acoustic logging data of rocks at different depths in a target sedimentary basin, obtaining a compaction trend of rock velocity with depth in the region; Based on the relationship between the target velocity difference and the pressure coefficient of the target sedimentary basin, the compaction trend, constructing the pressure prediction base model; Obtaining a hydrocarbon generation pressurization pressure coefficient difference, comprising: Based on the reconstructed P-wave velocity, calculating a pore pressure background value without hydrocarbon generation pressurization, and obtaining a reconstructed pore pressure background pressure; Subtracting the actually measured pore pressure from the reconstructed pore pressure background pressure, and obtaining the hydrocarbon generation pressurization pressure coefficient difference.

4. An electronic device, comprising: A computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the method for calculating the hydrocarbon generation pressurization contribution rate of high TOC oil shale according to any one of claims 1-2.

5. A computer readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the method for calculating the hydrocarbon generation pressurization contribution rate of high TOC oil shale according to any one of claims 1-2.

6. A computer program product comprising a computer program, characterized in that, The computer program is executed by a processor to implement the steps of the method for calculating the hydrocarbon generation pressurization contribution rate of high TOC oil shale according to any one of claims 1-2.

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