Method for analyzing mechanical characteristics of shale rock

Abstract

The invention discloses a shale rock mechanical characteristic analysis method, and relates to the technical field of petroleum and natural gas exploration, and the key points of the technical scheme are as follows: on the basis of rock physical experiment test and data analysis, designing experiments of organic geochemistry, physical properties, pore structures and mechanical parameters; conventional and imaging logging information is excavated by using an experimental depth; a continental facies shale strong heterogeneity physical property and pore structure logging evaluation technology, a continental facies shale gas layer different occurrence state gas content logging evaluation technology, a continental facies shale gas layer high-frequency phase change reservoir fracturing property logging evaluation technology and a continental facies shale gas layer logging comprehensive evaluation technology are developed and formed. And a well logging comprehensive evaluation technical system of the strong heterogeneous continental facies shale gas reservoir is established. By means of the method, shale gas reservoir distribution rule understanding can be formed, comprehensive combination of logging methods is achieved, field exploration and engineering application are effectively guided, and necessary logging evaluation technical support is provided for exploration and development of continental facies shale gas layers.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration, and more specifically, to a method for analyzing the mechanical characteristics of shale rock. Background Art

[0002] The continental shale gas in the Ordos Basin is widely distributed and has huge resource potential. The recoverable resources account for a high proportion of geological resources. Previous exploration has confirmed the existence of shale gas in the Yan'an area, but the single well production is relatively low, and large-scale production has not yet been achieved. Well logging evaluation technology is a key technology and means for shale gas exploration and development. Domestic well logging evaluation of shale gas layers mainly draws on foreign experience, and gradually formed a shale gas "seven properties" and "three qualities" well logging evaluation technology suitable for the marine geological characteristics of southern my country. Compared with marine shale gas, continental shale gas is very different, and well logging evaluation is more difficult. The exploration and development of continental shale gas and reservoir evaluation in the Yan'an area are in the initial exploration stage. Well logging evaluation is still one of the main technical bottlenecks for large-scale commercial development of continental shale gas in the Yan'an area. The well logging evaluation method used in marine shale gas exploration is difficult to fully adapt, and new evaluation technologies need to be developed based on the characteristics of continental shale gas reservoirs.

[0003] Due to the development of sand-mud interlayers and interlayers, rapid reservoir phase change, complex lithology, developed sandstone laminae, strong heterogeneity, low organic matter maturity, complex gas content, dense physical properties, strong plasticity, and complex logging environment (mud invasion and easy collapse), compared with marine shale gas, the continental shale gas layer in Yan'an has significant characteristics such as "strong heterogeneity", "complex occurrence state" and "medium-high plasticity". It is very difficult to use logging data to accurately calculate the parameters of continental shale gas reservoirs, quantitatively evaluate gas content, evaluate compressibility, and comprehensively classify and optimize the "sweet spots" of reservoirs. The main difficulties in logging evaluation are reservoir physical properties, gas content, and economic compressibility.

[0004] Therefore, the present invention aims to provide a method for analyzing the rock mechanical characteristics of mudstone, so as to carry out in-depth research on the unique characteristics of the continental shale gas layers in the Yan'an area from the aspects of the quality of continental strong heterogeneity shale reservoirs, the gas content of continental high-adsorption gas shale reservoirs, and the fracturing ability of continental high-frequency phase change shale reservoirs, so as to form a new logging technology that meets the needs of continental shale gas reservoir identification and evaluation. Summary of the invention

[0005] The purpose of the present invention is to provide a method for analyzing the rock mechanical characteristics of mudstone. The present invention develops and forms logging evaluation technology for the strong heterogeneity of physical properties and pore structure of continental shales, logging evaluation technology for gas content in different occurrence states of continental shale gas layers, logging evaluation technology for the fracturability of high-frequency phase change reservoirs in continental shale gas layers, and comprehensive logging evaluation technology for continental shale gas layers based on rock physics experimental tests and data analysis. A comprehensive logging evaluation technology system for strongly heterogeneous continental shale gas layers is established, which can form an understanding of the distribution law of shale gas reservoirs, be used to realize the comprehensive combination of logging methods, effectively guide field exploration and engineering applications, and provide necessary logging evaluation technical support for the exploration and development of continental shale gas layers.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: A method for analyzing the mechanical characteristics of shale rock, comprising the following steps: S1. Based on rock physics experimental tests and data analysis, combined with logging, mud logging, geological and engineering data, we designed targeted experiments on organic geochemistry, physical properties, pore structure and mechanical parameters around the three core issues of reservoir properties, gas content and fracturing ability; S2. Use the experimental depth to mine conventional and imaging logging information, closely combine production dynamics and engineering application requirements, and carry out the evaluation of the quality of continental strong heterogeneity shale reservoirs, the evaluation of the gas content of continental high-adsorption gas shale reservoirs, the evaluation of the fracturability of continental high-frequency phase change shale reservoirs, and the application of comprehensive logging evaluation technology for continental shale gas layers; S3. The four key logging evaluation technologies are finally formed through evaluation: logging evaluation technology for strong heterogeneity of continental shale physical properties and pore structure, logging evaluation technology for gas content in different occurrence states of continental shale gas layers, logging evaluation technology for fracturability of high-frequency phase change reservoirs in continental shale gas layers, and comprehensive logging evaluation technology for continental shale gas layers. S4. Through the evaluation technology, a comprehensive logging evaluation technology system for highly heterogeneous continental shale gas layers is established. On this basis, the enrichment characteristics of shale gas reservoirs based on detailed understanding of well logging are carried out, and the integrated geological and engineering description and evaluation of continental shale gas reservoirs based on well logging interpretation are carried out to form an understanding of the distribution law of shale gas reservoirs, which is used to realize the comprehensive use of well logging methods, effectively guide field exploration and engineering applications, and provide necessary logging evaluation technology support for the exploration and development of continental shale gas layers.

[0007] The present invention is further configured as follows: the process of applying the comprehensive evaluation technology of well logging in continental shale gas layers in step S2 is: conducting a well logging model compliance analysis, using the established well logging to identify shale gas layer sweet spots, determining the perforation and fracturing layer sections, conducting engineering construction monitoring on the effectiveness of the model, and then using the well logging gas reservoir research results to assist in drilling well site deployment, and verifying the application effect of the results through engineering construction.

[0008] The present invention is further configured as follows: the well logging evaluation technology for gas content in different occurrence states of continental shale gas layers in step S3 uses field observations, drilling coring data and logging data to deeply investigate the sedimentary characteristics of shale in the main target layer of the region, analyze its sedimentary environment, characterize the spatial distribution characteristics of organic-rich shale, and then analyze the petrological characteristics, mineral composition, and structural structure of the gas-bearing mud shale, pay attention to the development of sandy laminae, combine thin section observation and analysis test data, describe the pore structure characteristics, and reveal the storage performance of shale gas reservoirs.

[0009] The present invention is further configured as follows: the knowledge of the distribution law of shale gas reservoirs formed in step S4 is formed by comprehensively considering the geochemical indicators of the shale gas layer, the porosity distribution, the main occurrence state and gas content scale of the shale gas, establishing a shale gas logging interpretation model for different strata, and then carrying out relevant indicator interpretation work based on the model to reveal the enrichment and distribution law of shale gas.

[0010] The present invention is further configured as follows: the process of evaluating the quality of continental highly heterogeneous shale reservoirs in step S2 is: on the basis of identifying lithology by density clustering nearest neighbor method and quickly identifying lithology by using logging curves, a multi-parameter fine logging lithology identification technology and a siltaceous laminae identification and prediction technology and a fractal method are comprehensively established to predict siltaceous laminae; then, based on the fine porosity logging interpretation model, a lithology-based porosity quantitative evaluation method is established, which is used for formations with rapid lithology phase changes and strong heterogeneity.

[0011] The present invention is further configured as follows: the process of evaluating the fracturability of the continental high-frequency phase change shale reservoir in step S2 is: based on the geological characteristics of the Yanchang Formation shale in the region, starting from the triaxial mechanical test of mud shales with different lithologies and different mineral compositions under formation conditions, respectively analyzing their failure characteristics and brittle performance, clarifying the rock mechanical characteristics of mud shales with different lithologies, and on this basis, obtaining the calculation of logging mechanical parameters and mud shale brittleness evaluation, which provide a scientific basis for the optimization of favorable fracturing layers and scheme design of shale in the first area.

[0012] The present invention is further configured as follows: the integrated geological and engineering description and evaluation of continental shale gas reservoirs based on well logging interpretation in step S4 adopts a geological and engineering integrated seven-properties and three-quality shale gas sweet spot evaluation method and a shale gas reservoir seven-properties and three-quality visualized three-dimensional quantitative characterization method.

[0013] The present invention is further configured as follows: the geological and engineering integrated seven-property and three-quality shale gas sweet spot evaluation method includes establishing seven-property characteristics of three types of quality parameters, namely reservoir, source rock, and engineering mechanics, based on the four-property evaluation of conventional reservoirs according to shale gas identification and evaluation and drilling and completion engineering application requirements, comprehensively evaluating shale gas reservoirs, determining key parameters of terrestrial shale gas content, storage capacity, mobility and compressibility, establishing a reservoir evaluation parameter system and evaluation process, classifying and grading shale gas reservoirs, optimizing shale gas favorable areas, favorable layers and favorable fracturing sections, and providing a basis for predicting shale gas geological sweet spots and engineering sweet spots and drilling and fracturing.

[0014] The present invention is further configured as follows: the method for visualizing three-dimensional quantitative characterization of seven properties and three qualities of shale gas reservoirs includes obtaining the main parameters of the vertical lithology variation function by analyzing well data on the basis of fine interpretation of well logging data, obtaining three-dimensional probability bodies of various lithologies by controlling variables in three-dimensional space and using the Kriging algorithm, and then determining the lithology by comparing the sizes of various lithology probability bodies through variogram analysis to obtain a three-dimensional distribution body of the lithology body, performing attribute modeling using the porosity, permeability, TOC and hydrocarbon content attributes of the three-dimensional lithology body to distinguish it from conventional natural gas reservoirs, incorporating geochemical parameters, gas content parameters and mechanical parameters into the method category of attribute modeling, establishing a process and method for fine description of continental shale gas reservoirs, and being able to quantitatively characterize the attribute characteristics of the seven properties and three qualities of continental shale gas reservoirs in three-dimensional space.

[0015] In summary, the present invention has the following beneficial effects: 1. The present invention analyzes the compliance rate of the well logging model, uses the established well logging to identify the sweet spots in the shale gas layer, determines the perforation and fracturing layer section, and monitors the effectiveness of the model for engineering construction. At the same time, the well logging gas reservoir research results are used to assist in the deployment of drilling wells, and the application effect of the results can be effectively tested through engineering construction; 2. The present invention uses field observation, drilling coring data and logging data to deeply study the sedimentary characteristics of shale in the main target layer of the area, analyze its sedimentary environment, and describe the spatial distribution characteristics of organic-rich shale. At the same time, the petrological characteristics, mineral composition, and structural structure of gas-bearing mud shale, especially the internal structure of the shale layer, pay attention to the development of sandy laminae, combine thin section observation and analysis test data, describe the pore structure characteristics, and accurately reveal the storage performance of shale gas reservoirs; 3. The present invention establishes a shale gas logging interpretation model for different strata by comprehensively studying the geochemical indicators of the shale gas layers in the research area, the porosity distribution, the main occurrence state of shale gas, the gas content scale, etc., and carries out the interpretation of relevant indicators based on the model to accurately reveal the enrichment and distribution law of shale gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is a schematic diagram of a flow chart of a method for analyzing rock mechanical characteristics of shale in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following is combined with Figure 1 The present invention is described in further detail.

[0018] Embodiment: A method for analyzing rock mechanical characteristics of shale comprises the following steps: S1. Based on rock physics experimental tests and data analysis, combined with logging, mud logging, geological and engineering data, we designed targeted experiments on organic geochemistry, physical properties, pore structure and mechanical parameters around the three core issues of reservoir properties, gas content and fracturing ability; S2. Use the experimental depth to mine conventional and imaging logging information, closely combine production dynamics and engineering application requirements, and carry out the evaluation of the quality of continental strong heterogeneity shale reservoirs, the evaluation of the gas content of continental high-adsorption gas shale reservoirs, the evaluation of the fracturability of continental high-frequency phase change shale reservoirs, and the application of comprehensive logging evaluation technology for continental shale gas layers; S3. The four key logging evaluation technologies are finally formed through evaluation: logging evaluation technology for strong heterogeneity of continental shale physical properties and pore structure, logging evaluation technology for gas content in different occurrence states of continental shale gas layers, logging evaluation technology for fracturability of high-frequency phase change reservoirs in continental shale gas layers, and comprehensive logging evaluation technology for continental shale gas layers. S4. Through the evaluation technology, a comprehensive logging evaluation technology system for highly heterogeneous continental shale gas layers is established. On this basis, the enrichment characteristics of shale gas reservoirs based on detailed understanding of well logging are carried out, and the integrated geological and engineering description and evaluation of continental shale gas reservoirs based on well logging interpretation are carried out to form an understanding of the distribution law of shale gas reservoirs, which is used to realize the comprehensive use of well logging methods, effectively guide field exploration and engineering applications, and provide necessary logging evaluation technology support for the exploration and development of continental shale gas layers.

[0019] In this embodiment, two shale gas exploration and production areas, Xia Siwan-Ganquan District and Yanchang East District, were selected as key research objects, and gas reservoir logging geological research was carried out to test the logging model and other results. The logging model was corrected and improved according to actual application to guide the exploration area selection and fracturing layer selection. Xia Siwan-Ganquan District is located in the Xia Siwan-Ganquan area of ​​Yan'an area. The target stratum is the Chang 7 of the Mesozoic Yanchang Formation. The area of ​​the area is 693km2. 23 shale gas wells have been drilled in the area, covering most of the Mesozoic shale gas wells of Yanchang Group in recent years. The Yanchang East Research Area is a key research area of ​​the Upper Paleozoic, located in Yanchang and Yichuan. The target stratum is the Shanxi Formation of the Upper Paleozoic. The area of ​​the area is 2851km2. 9 horizontal wells, 4 vertical wells and more than 70 natural gas wells have been drilled in the area.

[0020] Through field geological surveys and experimental tests, 5 field profiles were observed, 130 outcrop samples were collected, and cores from 40 wells were observed. Combining hand specimens, mineral composition tests, microscopic observations, organic geochemical tests and other methods, the sedimentary characteristics of the mountain shale were systematically studied from multiple scales such as field outcrops, drilling cores and microscopic thin sections, and the stratigraphic framework was divided; a total of 395 samples of various types were sent for 2 pieces of hydrocarbon generation thermal simulation (nano-CT, argon ion polishing SEM), 20 pieces of vitrinite reflectance, 60 pieces of organic matter abundance (TOC), rock pyrolysis (Tmax, S1, S2, hydrogen Index) 30 pieces, gas content test 20 pieces, clay mineral analysis 30 pieces, whole rock diffraction analysis 21 pieces, full diameter core 3D CT imaging analysis 2 pieces, nano CT experiment 4 pieces, argon ion polishing SEM 20 pieces, specific surface area and pore size distribution 20 pieces, NMR movable fluid content analysis 20 pieces, NMR gas saturation analysis 20 pieces, rock mechanical properties analysis 8 pieces, rock fracture pressure 3 pieces, shale anisotropy parameters 15 pieces, core wettability experiment 10 pieces, shale infiltration and gas drive experiment 20 pieces, shale desorption matrix shrinkage experiment 20 pieces, stress sensitivity experiment 20 pieces. The relevant laboratories for related experiments have world-class experimental analysis equipment, which ensures the accuracy of the experimental results and provides strong technical support for the research work. After the collected samples were classified and sorted, various analysis tests were completed. The main test workload is shown in Table 1: Table 1 Sample test analysis statistics The contents completed in this embodiment include the study of shale gas identification methods, shale rock mineral composition analysis, shale reservoir performance and gas content evaluation, and shale rock mechanical characteristics evaluation; the study of shale gas identification methods is to establish a technical method for determining the organic carbon content of shale using logging data through the corresponding analysis of rock physics experimental analysis results and logging data, explore the logging evaluation technology related to maturity, and then form a key technology for shale gas identification; shale rock mineral composition analysis is to apply core analysis test data such as whole rock analysis, combined with density, lithology density logging, natural gamma and natural gamma spectrum logging and other logging data for comprehensive analysis, identify clay mineral types and contents, determine sand (siliceous quartz) content and carbonate rock material content, and form a key technology for evaluating shale gas. The key technology for evaluating the content of brittle materials such as mud (clay minerals), silica (sand), and lime (carbonate rock materials); the evaluation of shale reservoir performance and gas content is based on the rock electrical parameters of core analysis and rock physics experiments. After core calibration, the model and parameters for evaluating shale porosity, permeability, and saturation are determined based on nuclear magnetic logging data, forming a technical method for evaluating the above key parameters; and then exploring logging technology to determine the gas content of shale; the evaluation of shale rock mechanics characteristics is based on array sonic logging and other data to evaluate shale fractures, quantitatively calculate rock mechanics parameters such as shale fracture pressure, meet the requirements of establishing rock mechanics parameter calculation models, and guide the fracturing transformation of shale reservoirs; the specific situation of the physical workload completed and the preparation of drawings is shown in Table 2: Table 2 Research workload statistics In this embodiment, the well logging evaluation of the quality of the highly heterogeneous shale reservoir is based on the density clustering nearest neighbor method established in other topics to identify lithology, and the method of quickly identifying lithology using logging curves to comprehensively establish a multi-parameter fine logging lithology identification technology, a silt layer identification and prediction technology, and a fractal method to predict silt layers. It is suitable for formations with rapid lithological phase changes and strong heterogeneity, and the compliance rate reaches 90%; a lithology-based porosity quantitative evaluation method is established based on the fine porosity logging interpretation model (porosity-volume equation method, porosity-pyrite volume equation method); the geochemical quality logging evaluation of the continental shale reservoir is based on the existing method for calculating TOC. The univariate empirical formula method has a large limitation on the scope of the region and is poor in promotion and use. The multivariate empirical formula method has introduced multiple parameters for limitation, so the calculation accuracy is relatively low compared to the univariate empirical formula method. The degree is more accurate. Through practice, the ΔlogR method is less applicable in this area. Nuclear magnetic resonance-element logging-volume density and pulsed neutron-natural gamma spectroscopy are special logging methods. They are more accurate for single wells with special logging data, but they cannot be applied to a large number of wells without special logging. Therefore, this topic uses the ΔlogR multivariate regression formula method to interpret the TOC content in the area; the logging evaluation of the fracturability of continental high-frequency phase change shale reservoirs is based on the geological characteristics of the Yanchang Formation shale in the study area. Starting from the triaxial mechanical tests of mud shales with different lithologies and different mineral compositions under formation conditions, their failure characteristics and brittle performance are analyzed respectively, and the rock mechanical characteristics of mud shales with different lithologies are clarified. On this basis, the calculation of logging mechanical parameters and the evaluation of mud shale brittleness are explored, providing a scientific basis for the optimization of favorable fracturing layers and scheme design of shale in the study area.

[0021] The description and evaluation results of continental shale gas reservoirs based on fine logging interpretation include the geological and engineering integrated "seven properties and three qualities" shale gas "sweet spot" evaluation method and the shale gas reservoir "seven properties and three qualities" visualization three-dimensional quantitative characterization method; based on the application of geophysical methods to obtain the key parameters of shale gas layers, the shale gas geological and engineering integrated "seven properties and three qualities" favorable area evaluation method is established. Focusing on the needs of shale gas identification and evaluation and drilling and completion engineering applications, on the basis of the "four properties" evaluation of conventional reservoirs, the "seven property characteristics" of three types of quality parameters, namely reservoir, source rock, and engineering mechanics, are established to conduct a comprehensive evaluation of shale gas reservoirs, determine the key parameters of continental shale gas content, storage, mobility, and compressibility, establish a reservoir evaluation parameter system and evaluation process, classify and grade shale gas reservoirs, and select favorable shale gas areas, favorable layers, and favorable fracturing sections, providing a basis for the prediction of shale gas geological sweet spots and engineering sweet spots and drilling and fracturing.

[0022] On the basis of detailed interpretation of logging data, the main parameters of vertical lithology variogram are obtained by well data analysis. By controlling variables in three-dimensional space and using the Kriging algorithm, three-dimensional probability bodies of various lithologies are obtained, and then the lithology is determined by comparing the sizes of various lithology probability bodies through variogram analysis, thereby realizing the three-dimensional distribution of lithology bodies. On the basis of obtaining three-dimensional lithology bodies, attribute modeling, including porosity, permeability, TOC and hydrocarbon content, is also an important part of geological modeling. Different from conventional natural gas reservoirs, geochemical parameters, gas content parameters and mechanical parameters are included in the scope of attribute modeling methods for the first time, and the process and method of detailed description of continental shale gas reservoirs are established, and the attribute characteristics of "seven properties and three qualities" of continental shale gas reservoirs are quantitatively characterized in three-dimensional space.

[0023] On the basis of establishing a fine evaluation logging system for continental shale gas layers, the formed logging gas layer identification and evaluation technology was revised and improved, and the technology was further applied. The research results were applied to the verification of field work. Based on the construction of multi-attribute and multi-scale key attribute parameters, sweet spot evaluation and optimization were carried out to effectively improve the logging interpretation compliance rate. The logging evaluation parameter system and standards for favorable shale gas areas were established, favorable areas were predicted, and 715 km of the Mesozoic core area were selected. 2 , favorable area 3500 km 2 , Upper Paleozoic Shanxi Formation mountain favorable area 1940 km 2 . Shanli District 1832 km 2 , deployed 6 wells, systematically carried out research on gas layer identification and quantitative evaluation models in horizontal well sections, and carried out a lot of tracking interpretation and optimization adjustment work in field experiments. Before fracturing, pre-fracturing evaluation work was carried out to ensure that the field test wells achieved good results in drilling, fracturing and gas testing, and achieved remarkable application results.

[0024] In this embodiment, a logging curve standardization method is used. Currently, in multi-well evaluation and reservoir description, two-dimensional histograms, frequency cross plots, multi-dimensional histograms, trend surface analysis methods, mean-variance methods, etc. are generally used to standardize logging data. This standardization uses histograms and frequency cross plots to standardize logging data. The basic idea of ​​this method is to use the logging data of the standard layer of key wells that have been corrected for environmental impacts (such as neutrons, density, acoustic wave time difference, etc.) to make histograms (including multi-dimensional histograms) and frequency cross plots as the calibration mode for standardizing logging data. By analyzing the frequency distribution of the logging data of the standard layer of each well, and comparing them one by one with the oil field standard model, the reliability of the logging data of each well is checked, and the correction value is determined. The specific approach is: ① By comparing wells, find out the standard layer within the oil field (the condition of the standard layer is: it exists in every well, its logging curve has no serious wellbore influence, and is not affected by lithology and hydrocarbons), and select 2 to 3 of them as standard layers.

[0025] ② Make frequency cross-plots and histograms of the neutron, density and acoustic time difference measurement data for each standard layer.

[0026] ③ By comparing and finding out the overall changing trend of the frequency cross-plot or histogram of neutron, density and acoustic wave time difference of the standard layer of the oil field, the overall trend diagram of the standard layer of the entire oil field is obtained.

[0027] ④ Compare the frequency cross-plot or histogram of the logging data of each standard layer of each well with the corresponding oil field general trend diagram (for overlapping comparison). If the two coincide well, it means that the scale of the logging data of the well is correct; if the frequency cross-plot (or histogram) of a single well does not coincide well with the oil field standard model, it means that the logging data of the well may have a scale error, and the correction amount caused by the scale error should be further calculated.

[0028] ⑤ The method to determine the correction amount of single well logging data is to read the difference between the single well frequency cross-plot (or histogram) and the corresponding oil field general trend diagram. This difference is the correction value, and add it to the original logging data to obtain the standardized logging value.

[0029] This embodiment also adopts the probability of geological engineering integration. As an unconventional resource, shale gas must adopt the idea of ​​geological engineering integration to achieve scale-effective development. The overall requirement is to focus on geological research, integrate multiple disciplines and professions, and coordinate multiple engineering technologies. The core is to create a detailed three-dimensional geological model. In the application scenario of geological engineering integration, new requirements are put forward for the management and application of integrated modeling. Geological engineering integration emphasizes the interaction between geological research and operations. The support of geological models for engineering operations such as drilling and fracturing is an important purpose of modeling. Therefore, the modeling idea should adapt to unconventional research needs such as geomechanical simulation and fracturing simulation. Especially in the early stages of development, the uncertainty of geological models is relatively high, which requires that the geological model be quality controlled and updated based on new data and information continuously acquired during the progress of engineering operations, so as to achieve "timely modeling" and quantitatively represent the geological characteristics reflected by multidisciplinary data into the model, thereby supporting well site deployment, drilling, geological guidance, fracturing design and post-evaluation, and achieving a leap from one dimension to three dimensions, from qualitative to quantitative, and from local (single well) to overall (platform area, production area), ultimately realizing the efficient development of oil and gas fields.

[0030] Gas reservoir description is based on shale gas geology, combined with the latest computer and exploration technology, and linked to various data such as geology, logging, and gas reservoir engineering, and then quantitatively described in three-dimensional space. The purpose of gas reservoir description is to establish a three-dimensional geological model and a three-dimensional attribute model of the gas reservoir based on well points, combined with various information about gas reservoirs such as geology, logging, and seismic, to provide a favorable basis for improving the production and recovery rate of gas reservoirs. Shale gas, especially continental shale gas reservoirs, has completely different characterization methods from conventional gas reservoirs in terms of geological characteristics. At present, based on the above logging interpretation model, the key parameters of various shale gas layers are finely interpreted and applied to the quantitative and visual description, characterization and prediction of shale gas reservoir structural features, reservoir body morphology, geochemical characteristics, and gas-bearing characteristics. The typical high-yield continental shale gas reservoirs are finely dissected, and the spatial distribution of continental shale gas reservoirs is characterized in combination with the gas-bearing evaluation results, so as to use logging data to reveal the enrichment law of continental shale gas, and provide a technical basis for the well site deployment and pre-pressure evaluation of shale gas wells.

[0031] The research idea of ​​geological modeling is to integrate single well, test and lateral advance data, and take sedimentary petrology and stratigraphic sequence theory as guidance. On the basis of systematic regional sedimentary environment analysis, stratigraphic division and comparative study, and typical logging curve analysis, the research aims to analyze and summarize the sedimentary phase development characteristics of shale gas reservoirs, deeply characterize the shale distribution law, and carefully study the division standards of effective shale favorable areas, clarify the scale of gas reservoirs and the control factors of accumulation, and provide a geological basis for the scientific and efficient development of gas reservoirs in the later stage.

[0032] By establishing a fine evaluation logging system for continental shale gas layers, the formed logging gas layer identification and evaluation technology is revised and improved, and the technology is further applied. The research results are applied to the verification of field work, and sweet spot evaluation and optimization are carried out according to the logging interpretation results of multi-attribute and multi-scale key attribute parameters, which effectively improves the logging interpretation compliance rate. A logging evaluation parameter system and standard for favorable shale gas areas is established, favorable areas are predicted, well locations are deployed, and a systematic study of gas layer identification and quantitative evaluation models for horizontal well sections is carried out. A large amount of tracking interpretation and optimization adjustment work is carried out in field experiments. Pre-fracturing evaluation work is carried out before fracturing to ensure that the field test wells achieve good results in drilling, fracturing and gas testing, and significant application results have been achieved.

[0033] Conclusion: In this embodiment, a comprehensive logging evaluation technology system for strongly heterogeneous continental shale gas layers is established. According to various logging interpretation methods, the application effect analysis and evaluation of continental shale gas logging technology are carried out. According to production practice, it is improved and relevant logging interpretation methods are supplemented. Under different geological conditions, the comprehensive use of various logging methods is realized to establish a comprehensive logging evaluation technology system for strongly heterogeneous continental shale gas layers.

[0034] (1) Well logging evaluation of shale reservoir quality with strong heterogeneity Based on the density clustering nearest neighbor method for identifying lithology and the method of quickly identifying lithology using logging curves established in other topics, a multi-parameter fine logging lithology identification technology, siltaceous laminae identification and prediction technology, and fractal method for predicting siltaceous laminae are comprehensively established. These technologies are suitable for strata with rapid lithology phase changes and strong heterogeneity, with a compliance rate of 90%.

[0035] A lithology-based porosity quantitative evaluation method was established based on fine porosity logging interpretation models (porosity-volume equation method, porosity-pyrite-containing volume equation method).

[0036] (2) Geochemical quality logging evaluation of continental shale reservoirs According to the existing methods for calculating TOC, the univariate empirical formula method has greater restrictions on the scope of the region and is less suitable for promotion and use. The multivariate empirical formula method has more accurate calculation accuracy than the univariate empirical formula method due to the introduction of multiple parameters for restriction. Through practice, the ΔlogR method has poor applicability in this area. Nuclear magnetic resonance-element logging-volume density and pulse neutron-natural gamma spectroscopy are both special logging methods, which are more accurate for interpreting single wells with special logging data, but cannot be applied to a large number of wells without special logging. Therefore, this study area uses the multivariate empirical formula method to interpret the TOC content in the area.

[0037] (3) Well logging evaluation of fracturing properties of continental high-frequency phase change shale reservoirs According to the geological characteristics of the Yanchang Formation shale in the study area, starting from the triaxial mechanical tests of mud shales with different lithologies and mineral compositions under formation conditions, their failure characteristics and brittleness performance were analyzed respectively, and the rock mechanics characteristics of mud shales with different lithologies were clarified. On this basis, the calculation of logging mechanical parameters and the evaluation of mud shale brittleness were explored, providing a scientific basis for the optimization of favorable fracturing layers and scheme design of shale in the study area.

[0038] This embodiment is applied to field tests, and high-yield gas flows are obtained in multiple wells with remarkable field results. On the basis of establishing a fine evaluation logging system for continental shale gas layers, the formed logging gas layer identification and evaluation technology is corrected and improved, and the technology is further applied. The research results are applied to field work verification, and sweet spot evaluation and optimization are carried out based on the construction of multi-attribute and multi-scale key attribute parameters to effectively improve the logging interpretation compliance rate. By establishing a logging evaluation parameter system and standards for shale gas favorable areas, favorable areas are predicted, and a systematic study of gas layer identification and quantitative evaluation models for horizontal well sections is carried out. In addition, a large amount of tracking interpretation and optimization adjustment work is carried out in field experiments, and pre-fracturing evaluation work is carried out before fracturing to ensure that the field test wells achieve good results in drilling, fracturing and gas testing, and finally achieve remarkable application results.

[0039] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for analyzing rock mechanical characteristics of shale, characterized by: The following steps are involved: S1. Based on rock physics experimental tests and data analysis, combined with logging, mud logging, geological and engineering data, we designed targeted experiments on organic geochemistry, physical properties, pore structure and mechanical parameters around the three core issues of reservoir properties, gas content and fracturing ability; S2. Use the experimental depth to mine conventional and imaging logging information, closely combine production dynamics and engineering application requirements, and carry out the evaluation of the quality of continental strong heterogeneity shale reservoirs, the evaluation of the gas content of continental high-adsorption gas shale reservoirs, the evaluation of the fracturability of continental high-frequency phase change shale reservoirs, and the application of comprehensive logging evaluation technology for continental shale gas layers; S3. The four key logging evaluation technologies are finally formed through evaluation: logging evaluation technology for strong heterogeneity of continental shale physical properties and pore structure, logging evaluation technology for gas content in different occurrence states of continental shale gas layers, logging evaluation technology for fracturability of high-frequency phase change reservoirs in continental shale gas layers, and comprehensive logging evaluation technology for continental shale gas layers. S4. Through the evaluation technology, a comprehensive logging evaluation technology system for highly heterogeneous continental shale gas layers is established. On this basis, the enrichment characteristics of shale gas reservoirs based on detailed understanding of well logging are carried out, and the integrated geological and engineering description and evaluation of continental shale gas reservoirs based on well logging interpretation are carried out to form an understanding of the distribution law of shale gas reservoirs, which is used to realize the comprehensive use of well logging methods, effectively guide field exploration and engineering applications, and provide necessary logging evaluation technology support for the exploration and development of continental shale gas layers.

2. The method for analyzing rock mechanical characteristics of shale according to claim 1, characterized in that: The process of applying the comprehensive evaluation technology of well logging in continental shale gas layers in step S2 is as follows: conducting a well logging model compliance analysis, using the established well logging to identify shale gas layer sweet spots, determining the perforation and fracturing layer sections, conducting engineering construction monitoring on the effectiveness of the model, and then using the well logging gas reservoir research results to assist in the deployment of drilling well sites, and verifying the application effect of the results through engineering construction.

3. The method for analyzing rock mechanical characteristics of shale according to claim 1, characterized in that: The well logging evaluation technology for gas content in different occurrence states of continental shale gas layers in step S3 uses field observations, drilling coring data and logging data to deeply understand the sedimentary characteristics of shale in the main target layer of the region, analyze its sedimentary environment, characterize the spatial distribution characteristics of organic-rich shale, and then analyze the petrological characteristics, mineral composition, and structural structure of gas-bearing mud shale, pay attention to the development of sandy laminae, combine thin section observation and analysis test data, describe the pore structure characteristics, and reveal the storage performance of shale gas reservoirs.

4. The method for analyzing rock mechanical characteristics of shale according to claim 1, characterized in that: The knowledge of the distribution law of shale gas reservoirs in step S4 is formed by comprehensively considering the geochemical indicators of the shale gas layers, the porosity distribution, the main occurrence state and gas content of shale gas, establishing a shale gas logging interpretation model for different layers, and then conducting relevant indicator interpretation work based on the model to reveal the enrichment and distribution law of shale gas.

5. The method for analyzing rock mechanical characteristics of shale according to claim 1, characterized in that: The process of evaluating the quality of continental highly heterogeneous shale reservoirs in step S2 is as follows: based on the density clustering nearest neighbor method to identify lithology and the method of quickly identifying lithology using logging curves, a multi-parameter fine logging lithology identification technology and a silt sandy laminae identification and prediction technology and a fractal method to predict silt sandy laminae are comprehensively established; then, based on the fine porosity logging interpretation model, a lithology-based porosity quantitative evaluation method is established for formations with rapid lithology phase changes and strong heterogeneity.

6. The method for analyzing rock mechanical characteristics of shale according to claim 1, characterized in that: The process of evaluating the fracturability of the continental high-frequency phase change shale reservoir in step S2 is as follows: based on the geological characteristics of the Yanchang Formation shale in the region, starting from the triaxial mechanical test of mud shales with different lithologies and different mineral compositions under formation conditions, respectively analyzing their failure characteristics and brittle performance, clarifying the rock mechanical characteristics of mud shales with different lithologies, and on this basis, obtaining the calculation of logging mechanical parameters and mud shale brittleness evaluation, which provide a scientific basis for the optimization of favorable fracturing layers and scheme design of shale in the first area.

7. The method for analyzing rock mechanical characteristics of shale according to claim 2, characterized in that: The integrated description and evaluation of terrestrial shale gas reservoirs based on well logging interpretation in step S4 adopts an integrated geology-engineering method for evaluating shale gas sweet spots with seven properties and three qualities and a visualized three-dimensional quantitative characterization method for seven properties and three qualities of shale gas reservoirs.

8. A method for analyzing rock mechanical characteristics of shale according to claim 7, characterized in that: The geological and engineering integrated seven-property and three-quality shale gas sweet spot evaluation method includes establishing seven-property characteristics of three types of quality parameters, namely reservoir, source rock, and engineering mechanics, based on the four-property evaluation of conventional reservoirs according to the requirements of shale gas identification and evaluation and drilling and completion engineering applications, and comprehensively evaluating shale gas reservoirs, determining key parameters of gas content, storage capacity, mobility and compressibility of continental shales, establishing a reservoir evaluation parameter system and evaluation process, classifying and grading shale gas reservoirs, and optimizing favorable shale gas areas, favorable layers and favorable fracturing sections, so as to provide a basis for predicting shale gas geological sweet spots and engineering sweet spots and drilling and fracturing.

9. The method for analyzing rock mechanical characteristics of shale according to claim 1, characterized in that: The method for visualizing three-dimensional quantitative characterization of seven properties and three qualities of shale gas reservoirs includes obtaining the main parameters of the vertical lithology variation function by analyzing well data on the basis of detailed interpretation of well logging data, obtaining three-dimensional probability bodies of various lithologies by controlling variables in three-dimensional space and using the Kriging algorithm, and then determining the lithology by comparing the sizes of various lithology probability bodies through variogram analysis to obtain a three-dimensional distribution body of the lithology body, performing attribute modeling using the porosity, permeability, TOC and hydrocarbon content attributes of the three-dimensional lithology body to distinguish it from conventional natural gas reservoirs, incorporating geochemical parameters, gas content parameters and mechanical parameters into the method scope of attribute modeling, establishing a process and method for detailed description of continental shale gas reservoirs, and being able to quantitatively characterize the attribute characteristics of the seven properties and three qualities of continental shale gas reservoirs in three-dimensional space.

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