Method for predicting fracture development laws of carbonate rocks with different lithological characters
By combining rock compression experiments and well logging curves with three-dimensional geological modeling, the problem of predicting the development pattern of fractures in carbonate rocks of different lithologies was solved, enabling accurate identification of underground fractures and effective exploration of reservoirs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-22
- Publication Date
- 2026-05-22
AI Technical Summary
Existing technologies struggle to accurately predict fracture development patterns in carbonate rocks of different lithologies, leading to significant differences in reservoir quality and productivity between wells in carbonate oil and gas fields. Conventional and unconventional logging methods are either costly or lack sufficient accuracy, while seismic data has low resolution and cannot differentiate between lithologies.
By simulating fracture development under different confining pressures using rock compression experiments, and combining core calibration logging curves and three-dimensional geological modeling, we can identify and match the lithology of each single well and establish a predictive model for fracture development.
It enables accurate prediction of fractures in carbonate rocks of different lithologies underground, improves the success rate of exploration deployment, provides a reliable basis for identifying reservoir development zones, and the method is highly operable and has high application value.
Smart Images
Figure CN122071944A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of this invention relate to oil and gas exploration technology, and in particular to a method for predicting the development law of fractures in carbonate rocks of different lithologies. Background Technology
[0002] Marine carbonate oil and gas reservoirs, accounting for 60% of the world's total oil and gas production, have always been a key focus of global oil and gas exploration. Similarly, with the increasing exploration efforts in carbonate oil and gas, my country has discovered a series of medium- to large-sized carbonate oil and gas fields in the Ordos Basin, Tarim Basin, Sichuan Basin, and Bohai Bay Basin over the past 30 years, demonstrating their enormous potential. Fractures in carbonate reservoirs increase reservoir space and provide seepage channels, making them an important component of high-quality reservoirs. However, fracture development in carbonate rocks is complex. Even under the same sedimentary facies and tectonic stress environment, fracture development varies among different lithologies of carbonate rocks, resulting in significant differences in reservoir quality and productivity between wells within carbonate oil and gas fields.
[0003] Currently, there are few publications and patents on predicting fracture development patterns in carbonate rocks of different lithologies, mainly relying on techniques such as outcrops, cores, well logging, and seismic analysis. However, these methods have some limitations. For example, while petrological methods such as outcrops, cores, and thin sections can provide intuitive information, the development of surface fractures without confining pressure differs from that of underground fractures with confining pressure, thus making it impossible to accurately predict underground fracture development patterns. Well logging for fracture prediction can be divided into conventional and unconventional logging methods. Conventional logging mainly refers to the response of nine conventional logging curves to fractures, but it usually requires combining multiple curves and is easily affected by infill materials, resulting in insufficient accuracy in fracture prediction. Unconventional logging mainly includes FMI logging, CT scanning, and acoustic remote sensing technology. Although unconventional logging has higher accuracy than conventional logging, it is expensive, and in actual oilfield research, only a small number of wells can be tested, resulting in limited data for prediction. Seismic data has a large resolution scale, and methods for identifying fractures based on seismic data lack precision. Furthermore, current methods at most differentiate between dolomite and limestone within carbonate rocks to explore differences in fracture development between the two lithologies, without further subdividing the lithology. This is clearly insufficient to support carbonate oil and gas exploration. Therefore, accurately predicting fracture development patterns in carbonate rocks of different lithologies is crucial to improving the success rate of carbonate oil and gas exploration deployments. Summary of the Invention
[0004] To address the aforementioned technical problems, at least one embodiment of the present invention provides a method for predicting the development pattern of fractures in carbonate rocks of different lithologies.
[0005] In some optional embodiments, the method mainly includes the following steps:
[0006] The target strata in the study area were classified by lithology, and the fracture development characteristics of different lithologies were analyzed.
[0007] By simulating the fracture development of different lithologies under different confining pressures at different burial depths in the study area through rock compression experiments, the fracture development patterns of different lithologies were obtained.
[0008] The lithology of each well in the study area was identified by using the logging curves calibrated with core samples, and the lithology interpretation results of each well were obtained.
[0009] By matching the fracture development patterns of different lithologies with the lithology interpretation results of each single well, the fracture development status of the target layer in each single well in the study area can be obtained.
[0010] Based on the interpretation results of different lithologies and fracture development of the target layer in each single well, the fracture development of the target layer in the study area is predicted using three-dimensional geological modeling.
[0011] In some alternative embodiments, the crack development characteristics include the crack dip angle, aperture, and different dip angle filling conditions, as well as at least one characteristic of the crack filling material.
[0012] In some optional embodiments, the step of simulating fracture development of different lithologies under different confining pressures at different burial depths in the study area through core experiments to obtain fracture development patterns of different lithologies includes:
[0013] The burial depth and confining pressure are set such that the confining pressure increases by 10 MPa for every 1000m increase in burial depth.
[0014] In some optional embodiments, the step of identifying the lithology of each well in the study area using logging curves calibrated with core samples and obtaining lithology interpretation results for each well includes:
[0015] Based on core calibration, a lithology identification chart is established using the response values of well logging curves to different lithologies as the standard.
[0016] The lithology in the target layer of each well in the study area was identified using a lithology identification chart, and each lithology was distinguished by different symbols.
[0017] In some optional embodiments, the logging curve is a lithology-sensitive logging curve.
[0018] In some optional embodiments, the logging curves include natural gamma and sonic transit time curves.
[0019] In some optional embodiments, the prediction of fracture development in the target layer of the study area using three-dimensional geological modeling methods includes:
[0020] The longitudinal and transverse predictions of fracture development in the target layer of the study area were conducted to determine the location of the most favorable lithology for fracture development, as well as the fracture development characteristics and patterns in that lithology.
[0021] At least one embodiment of the present invention also provides a device for predicting the development pattern of fractures in carbonate rocks of different lithologies, characterized in that it comprises:
[0022] The analysis module is used to classify the target layer in the study area by lithology and analyze the fracture development characteristics of different lithologies; the experimental module is used to simulate the fracture development of different lithologies under different confining pressures in different burial depths in the study area through rock compression experiments, and to obtain the fracture development law of different lithologies.
[0023] The interpretation module is used to identify the lithology of each well in the study area using the logging curves calibrated by the core, and to obtain the lithology interpretation results of each well.
[0024] The matching module is used to match the fracture development patterns of different lithologies with the lithology interpretation results of each single well to obtain the fracture development status of the target layer in each single well in the study area.
[0025] The prediction module is used to predict the fracture development of the target layer in the study area based on the interpretation results of different lithologies and fracture development of each single well using three-dimensional geological modeling methods.
[0026] At least one embodiment of the present invention also provides an electronic device, characterized in that it comprises:
[0027] At least one processor; and,
[0028] A memory communicatively connected to the at least one processor; wherein,
[0029] The memory stores instructions that can be executed by the at least one processor, which enables the at least one processor to perform the previously described method for predicting the fracture development patterns of carbonate rocks of different lithologies.
[0030] At least one embodiment of the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the method for predicting the development pattern of fractures in carbonate rocks of different lithologies as described above.
[0031] At least one embodiment of the present invention also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the method for predicting the fracture development patterns of carbonate rocks of different lithologies as described above.
[0032] This invention provides a method for predicting the development pattern of fractures in carbonate rocks of different lithologies. The method is implemented through the following steps: (1) lithological classification of the target layer and investigation of fracture development overview; (2) selection of representative lithologies suitable as reservoirs, and analysis of fracture development patterns under different confining pressures using rock compression experiments; (3) refinement and interpretation of the lithology of each well using well logging curves calibrated with core samples; (4) comparison and matching of experimental results with well logging curve interpretation results; (5) based on the interpretation results of each well, continuous vertical and horizontal prediction of fracture development in the target layer of the study area using three-dimensional geological modeling. This invention combines actual petrological observation, indoor rock simulation experiments, well logging interpretation, and three-dimensional modeling to accurately predict the development patterns of fractures in carbonate rocks of different lithologies at the surface and underground, helping to find fractured reservoir development areas and providing a reliable basis for exploration deployment. Furthermore, this invention is highly operable, with intuitive and clear identification, and has high application value. Its methods and steps can be easily promoted and applied to the exploration and development of fractured carbonate reservoirs. Attached Figure Description
[0033] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, and these illustrative descriptions do not constitute a limitation on the embodiments.
[0034] Figure 1 This is a flowchart illustrating the steps of the method for predicting the fracture development pattern of carbonate rocks of different lithologies according to an embodiment of the present invention.
[0035] Figure 2 This is a schematic diagram of the statistical results of fracture development characteristics in four different lithologies of carbonate rocks in Block X of this invention.
[0036] Figure 3 This is a schematic diagram showing the results of rock compression experiments on four different types of carbonate rocks in Block X under different confining pressure conditions according to an embodiment of the present invention;
[0037] Figure 4 This is a schematic diagram of a well logging identification chart for different lithologies of dolomite in Block X, according to an embodiment of the present invention;
[0038] Figure 5 This is a schematic diagram of the well logging interpretation and experimental matching results of well Y33 in block X of this invention.
[0039] Figure 6 This is a schematic diagram of the three-dimensional lithological model of layer W in block X of this invention. Detailed Implementation
[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the embodiments of the present invention to facilitate a better understanding of the invention. However, the technical solutions claimed in the present invention can be implemented even without these technical details and various variations and modifications based on the following embodiments. The division of the following embodiments is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.
[0041] As mentioned earlier, accurate prediction of fractures in carbonate rocks of different lithologies is crucial for improving exploration success rates. Traditional prediction methods struggle to predict the development patterns of underground fractures after further subdivision of lithologies. Addressing the challenges of predicting fracture development in carbonate rocks of different lithologies, this invention proposes a method for predicting the development patterns of fractures in carbonate rocks of different lithologies.
[0042] Example 1
[0043] like Figure 1 As shown, the implementation steps of this method are as follows:
[0044] (1) Target strata lithological classification and fracture development overview survey
[0045] The relevant regions and stratigraphic layers were selected as the study area and target layer. A regional geological background survey was then conducted on the target layer to clarify its sedimentary pattern and tectonic evolution characteristics. Based on the regional geological background, and combined with the statistical results of field outcrops, core samples, and well logging observations, the lithology of the target layer in the study area and the fracture development characteristics of different lithologies were identified in detail.
[0046] (2) Select representative lithologies that can be used as reservoirs, and use rock compression tests to analyze the fracture development patterns of different lithologies under different confining pressures.
[0047] Based on geological conditions, representative lithologies from step (1) that can be used as reservoirs are selected. For example, cylindrical plunger samples with a diameter of 25 mm and a length of 50 mm are drilled from their corresponding outcrops or core samples. Uniaxial and triaxial rock compression tests are used to apply different confining pressures to the plunger samples to simulate the fracture development patterns of different lithologies under different burial depths (e.g., an increase of 10 MPa in confining pressure for every 1000 m increase in burial depth).
[0048] (3) Use the logging curves calibrated with core samples to refine the identification and interpretation of lithology in each well.
[0049] Well logging curves sensitive to lithological changes were selected, and lithological identification charts were established in conjunction with core calibration. The lithology in the target layer of each well in the study area was interpreted and identified in detail, and each lithology was distinguished by different symbols.
[0050] (4) Compare and match the experimental results with the well logging curve interpretation results.
[0051] The fracture development patterns of different lithologies obtained in step (2) are matched with the lithology interpretation results of each single well obtained in step (3) to obtain the fracture development map of the target layer of a single well.
[0052] (5) Based on the interpretation results of single wells, a three-dimensional geological model of the target layer in the study area is established using the three-dimensional geological modeling method to achieve continuous prediction of its fracture development in both the vertical and horizontal directions.
[0053] Based on the interpretation results of different lithologies and fracture development of each target layer obtained in step (4), a three-dimensional model of the target layer lithology in the study area is established using three-dimensional modeling software, so that the fracture development law of carbonate rocks of different lithologies in the target layer can be predicted vertically and horizontally.
[0054] Example 2
[0055] The technical details and effects of the above-described method of the present invention are explained in detail below with reference to examples.
[0056] The above method was applied to predict the fracture development pattern in the W layer of block X, and it showed very good results.
[0057] (1) The W stratum in Block X is a predominantly Precambrian dolomite sedimentary formation, with well-developed fractures, making it a typical example for studying the fracture development patterns in carbonate rocks of different lithologies. Based on the regional geological background, its sedimentary pattern and tectonic evolution characteristics were clarified. Furthermore, combining the statistical results of field outcrops, core samples, and well logging observations, the reservoir rock types in the W stratum were subdivided into four major categories based on different structures contained in the dolomite: micritic dolomite, brecciated dolomite, stromatolitic dolomite, and siliceous dolomite. The dip angle, aperture, and filling characteristics of the fractures within these categories were statistically analyzed. For example... Figure 2 As shown, A represents the statistical distribution of fracture dip angles in carbonate rocks of different lithologies; B represents the statistical results of fracture aperture; C represents the distribution of fracture filling at different dip angles; and D represents the statistical distribution of filling materials in the fractures.
[0058] (2) Cylindrical plunger samples with a diameter of 25 mm and a length of 50 mm were drilled from the cores of the four lithologies in step (1). Three intact plunger samples without surface cracks were selected for each lithology. Based on the actual geological conditions, uniaxial and triaxial rock compression methods were used to apply confining pressures of 0 MPa, 20 MPa, and 40 MPa to the plunger samples to simulate the fracture development patterns of different lithologies at the surface, 2 km, and 4 km burial depths. The experimental results are as follows: Figure 3 As shown in the figure. The results indicate that under 0 MPa confining pressure, there are a large number of fractures in each lithology, mainly splitting fractures along the stress direction. Under confining pressure, the number of fractures in micritic dolomite decreases sharply, and stress is concentrated and released at the weakest surface, mainly high-angle shear fractures. In brecciated dolomite, there are many weak surfaces, and the fractures are mainly high-angle fractures, which are relatively well-developed. In stromatolite dolomite, fractures mostly develop along algal striations, and their number is reduced compared to when there is no confining pressure. In siliceous dolomite, high-angle fractures are restricted by siliceous bands, and stress is released at the siliceous bands, forming fine microcracks.
[0059] (3) Selecting natural gamma and sonic transit time curves, combined with core calibration, and using the response values of well logging curves to different lithologies as the standard, establish identification charts for dolomite of different lithologies. This allows for the detailed identification of micritic dolomite, brecciated dolomite, stromatolite dolomite, and siliceous dolomite in the W layer of each single well in the study area, and distinguishes each lithology using different graphical representations. For example... Figure 4 As shown.
[0060] (4) Match the fracture development patterns of different lithologies obtained in step (2) with the lithology interpretation results of each single well obtained in step (3) to obtain the fracture development map of the target layer of a single well, taking well Y33 as an example. Figure 5 As shown.
[0061] (5) Based on the interpretation results of different lithologies and fracture development of each target layer obtained in step (4), a three-dimensional lithological model of layer W in block X is established using three-dimensional modeling software. For example... Figure 6 As shown, the distribution patterns of different lithologies are clearly visible in the model, which allows us to determine the location of the most favorable lithology for fracture development, as well as the characteristics and patterns of fracture development in that lithology, providing strong support for exploration deployment.
[0062] The technology proposed in this invention can be well applied to predicting the development patterns of fractures in carbonate rocks of different lithologies. By combining actual petrological observation, laboratory experiments, well logging interpretation, and 3D modeling, it is possible to accurately predict the development patterns of fractures in carbonate rocks of different lithologies both on the surface and underground, which helps in finding fractured reservoir development zones. The method and steps can be easily extended and applied to the exploration and development of fractured carbonate reservoirs.
[0063] Example 3
[0064] Another embodiment of the present invention relates to a device for predicting the development pattern of fractures in carbonate rocks of different lithologies, comprising:
[0065] The analysis module is used to classify the target strata in the study area by lithology and analyze the fracture development characteristics of different lithologies.
[0066] The experimental module is used to simulate the crack development of different lithologies under different confining pressures in different burial depths of the study area through rock compression experiments, and to obtain the crack development law of different lithologies.
[0067] The interpretation module is used to identify the lithology of each well in the study area using the logging curves calibrated by the core, and to obtain the lithology interpretation results of each well.
[0068] The matching module is used to match the fracture development patterns of different lithologies with the lithology interpretation results of each single well to obtain the fracture development status of the target layer in each single well in the study area.
[0069] The prediction module is used to predict the fracture development of the target layer in the study area based on the interpretation results of different lithologies and fracture development of each single well using three-dimensional geological modeling methods.
[0070] Example 4
[0071] Another embodiment of the present invention relates to an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the methods for predicting the fracture development patterns of different lithologies of carbonate rocks in the above embodiments.
[0072] The memory and processor are connected via a bus, which can include any number of interconnecting buses and bridges, connecting various circuits of one or more processors and memories. The bus can also connect various other circuits, such as peripheral devices, voltage regulators, and power management circuits, which are well known in the art and will not be described further herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be a single element or multiple elements, such as multiple receivers and transmitters, providing a unit for communicating with various other devices over a transmission medium. Data processed by the processor is transmitted over the wireless medium via an antenna, which further receives data and transmits it to the processor.
[0073] The processor manages the bus and general processing, and also provides various functions, including timing, peripheral interfaces, voltage regulation, power management, and other control functions. Memory is used to store data used by the processor during operation.
[0074] Example 5
[0075] Another embodiment of the present invention relates to a computer-readable storage medium storing a computer program. When executed by a processor, the computer program implements the method for predicting the fracture development patterns of carbonate rocks of different lithologies described in the above embodiments.
[0076] That is, those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a device (which may be a microcontroller, chip, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.
[0077] Example 6
[0078] Another embodiment of the present invention relates to a computer program product, including a computer program that, when executed by a processor, implements the steps of the method for predicting the fracture development patterns of carbonate rocks of different lithologies described in the above embodiments.
[0079] Those skilled in the art will understand that the above embodiments are specific embodiments for implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.
Claims
1. A method for predicting the development pattern of fractures in carbonate rocks of different lithologies, characterized in that, Includes the following steps: The target strata in the study area were classified by lithology, and the fracture development characteristics of different lithologies were analyzed. By simulating the fracture development of different lithologies under different confining pressures at different burial depths in the study area through rock compression experiments, the fracture development patterns of different lithologies were obtained. The lithology of each well in the study area was identified by using the logging curves calibrated with core samples, and the lithology interpretation results of each well were obtained. By matching the fracture development patterns of different lithologies with the lithology interpretation results of each single well, the fracture development status of the target layer in each single well in the study area can be obtained. Based on the interpretation results of different lithologies and fracture development of the target layer in each single well, the fracture development of the target layer in the study area is predicted using three-dimensional geological modeling.
2. The method for predicting the development law of fractures in carbonate rocks of different lithologies according to claim 1, characterized in that, The crack development characteristics include the crack dip angle, aperture, and filling conditions at different dip angles, as well as at least one characteristic of the crack filling material.
3. The method for predicting the development law of fractures in carbonate rocks of different lithologies according to claim 1, characterized in that, The study simulated fracture development of different lithologies at different burial depths under varying confining pressures using core experiments in the research area, obtaining fracture development patterns for different lithologies, including: The burial depth and confining pressure are set such that the confining pressure increases by 10 MPa for every 1000m increase in burial depth.
4. The method for predicting the development pattern of fractures in carbonate rocks of different lithologies according to claim 1, characterized in that, The method of using logging curves calibrated with core samples to identify the lithology of each well in the study area and obtaining lithological interpretation results for each well includes: Based on core calibration, a lithology identification chart is established using the response values of well logging curves to different lithologies as the standard. The lithology in the target layer of each well in the study area was identified using a lithology identification chart, and each lithology was distinguished by different symbols.
5. The method for predicting the development pattern of fractures in carbonate rocks of different lithologies according to claim 4, characterized in that, The logging curves mentioned are lithology-sensitive logging curves.
6. The method for predicting the development law of fractures in carbonate rocks of different lithologies according to claim 5, characterized in that, The logging curves include natural gamma and sonic transit time curves.
7. The method for predicting the development law of fractures in carbonate rocks of different lithologies according to claim 1, characterized in that, The method of predicting fracture development in the target layer of the study area using three-dimensional geological modeling includes: The longitudinal and transverse predictions of fracture development in the target layer of the study area were conducted to determine the location of the most favorable lithology for fracture development, as well as the fracture development characteristics and patterns in that lithology.
8. A device for predicting the development pattern of fractures in carbonate rocks of different lithologies, characterized in that, include: The analysis module is used to classify the target strata in the study area by lithology and analyze the fracture development characteristics of different lithologies. The experimental module is used to simulate the crack development of different lithologies under different confining pressures in different burial depths of the study area through rock compression experiments, and to obtain the crack development law of different lithologies. The interpretation module is used to identify the lithology of each well in the study area using the logging curves calibrated by the core, and to obtain the lithology interpretation results of each well. The matching module is used to match the fracture development patterns of different lithologies with the lithology interpretation results of each single well to obtain the fracture development status of the target layer in each single well in the study area. The prediction module is used to predict the fracture development of the target layer in the study area based on the interpretation results of different lithologies and fracture development of each single well using three-dimensional geological modeling methods.
9. An electronic device, characterized in that, include: At least one processor; as well as, A memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, which, when executed by the at least one processor, enables the at least one processor to perform the method for predicting the fracture development patterns of carbonate rocks of different lithologies as described in any one of claims 1 to 7.
10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the method for predicting the development law of fractures in carbonate rocks of different lithologies as described in any one of claims 1 to 7.