Method and system for predicting abnormal high pressure of carbonate rock under multi-physics field coupling effect

Abstract

The invention relates to the field of oil exploration and development, in particular to a carbonate rock abnormal high pressure prediction method and system under the multi-physics field coupling effect, and the method comprises the steps: obtaining various basic data of a stratum of a research area; carrying out fracture detection, energy attribute description and curvature calculation from an earthquake perspective; carrying out geologic structure modeling, exporting model data, and then carrying out random fracture distribution calculation, so that a geologic model is close to an actual stratum fracture state; carrying out rock mechanical analogue simulation; on the basis of carbonate rock stratum fracture and micro-fracture random simulation and fluid detection, local grid encryption is carried out at fracture and micro-fracture positions, and stress concentration coefficient distribution is simulated; and comprehensively judging the abnormal high pressure existence area of the carbonate rock stratum. By simulating the formation pore pressure change under the multi-physics field fluid-solid coupling effect, the prediction and forecast accuracy and the safe drilling efficiency of the oil and gas well drilling abnormal high pressure under the carbonate rock complex geological condition are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum exploration and development, and in particular to a method and system for predicting abnormally high pressure of carbonate rocks under the coupling effect of multiple physical fields. Background Art

[0002] According to statistics, more than 50% of the oil and gas field reservoirs in the world are carbonate fractures and cave reservoirs, which are so-called fracture-cavity reservoirs. In oil field exploration and development, seismic data are often used to study fracture-cavity systems and predict reservoirs, forming a relatively mature theory that has been widely used in production practice.

[0003] However, in the traditional carbonate formation pressure prediction process, Eaton and effective stress methods are mostly used, and their data source is based on seismic velocity. However, the seismic velocity is not accurate enough to describe the details of carbonate formation pressure, resulting in many abnormally high-pressure wells being drilled outside the seismic identification zone, which seriously affects drilling efficiency and safety.

[0004] Based on this, the present invention proposes a method and system for predicting abnormally high pressure in carbonate rocks under the coupling of multiple physical fields. It adopts the fluid-solid coupling of multiple physical fields such as temperature field, pressure field, fracture damage, and stress field and combines seismic attribute fusion to simulate the abnormally high pressure state and distribution probability of carbonate rock formations. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a method and system for predicting abnormally high pressure of carbonate rocks under the coupling of multiple physical fields.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling, comprising the following steps:

[0007] S1: Obtain basic data of the strata in the study area;

[0008] S2: From the perspective of seismic, fracture detection, energy attribute characterization, and curvature calculation are performed; geological structure modeling is performed, and after exporting the model data, random fracture distribution calculation is performed using MATLAB+COMSOL, combined with real drilling imaging logging, core fracture distribution, and seismic fracture detection results.

[0009] S3: Carry out rock physics calculations and rock mechanics simulations;

[0010] S4: Based on the random simulation of fractures and microfractures in carbonate formations and fluid detection, local mesh encryption is performed at fractures and microfractures to simulate the distribution of stress concentration factors;

[0011] S5: Comprehensively determine the areas where abnormally high pressure exists in carbonate formations.

[0012] The present invention is further configured such that the basic data in step S1 includes seismic data, structures, faults, completion data, well logging, oil testing, and fluid PVT of the study area.

[0013] The present invention is further configured such that the source of the seismic data is a seismic data body, including a .sgy format file and a .txt format file of structure, stratigraphic and fracture data.

[0014] The purpose of the above steps is to collect and organize the basic data in the early stage. The data source is the seismic data body, including .sgy and .txt files such as structure, stratigraphy, and fault. These data can be exported on DSG or other seismic software platforms. In addition, there are completed drilling data in the study area, including drilling, logging, well logging, oil and production test data, and PVT data on fluid properties.

[0015] The present invention is further configured that step S2 specifically includes the following steps:

[0016] S21: Import the .sgy and horizon files of the seismic data volume in the study area into the seismic software for fracture coherence detection, energy attribute characterization and curvature calculation;

[0017] S22: using the structure, layer, and fracture data to perform geological structure modeling, and deriving corresponding geological model data, and using MATLAB to perform random fracture calculations;

[0018] S23: Correct the fracture prediction model based on the actual drilling imaging logging data and core data, and generate a fracture file;

[0019] S24: Import the generated fracture file into COMSOL Multiphysics software for further fine modeling; used for subsequent rock mechanics simulation under given multi-physics field conditions;

[0020] S25: The results of seismic software and geological model simulation are imported into Petrel, and compared and differentiated by combining actual drilling imaging logging and core fracture distribution to make the geological model close to the actual formation fracture state.

[0021] The present invention is further configured such that the multi-physical field conditions include temperature, pressure, stress and fluid flow.

[0022] The present invention is further configured such that the seismic software uses Landmark DSG or Paradigm software for calculation.

[0023] The present invention is further configured such that the geological structure modeling is performed using any one of the softwares Petrel, SKUA-GOCAD, and JewelSuiteSubsurface Modeling.

[0024] The present invention is further configured such that step S3 specifically comprises obtaining the mechanical parameters of the rock based on the logging data, performing rock mechanics simulation based on the mechanical parameters under the conditions of the measured formation temperature, performing activity analysis of the simulated fracture and fracture mechanics damage simulation, and calculating the ground stress.

[0025] The principle of fracture activity is actually based on friction theory and the study of critical stress of faults under the Mohr-Coulomb criterion. Fault zone damage is the damage simulation in the simulation software. The rock reaches the cracking condition, the relationship between stress and strain, and as the force increases, the degree of rock fracture increases, the expansion morphology of the crack and the damage increase.

[0026] The present invention is further configured such that step S4 specifically comprises, based on the fracture activity analysis and fracture mechanics damage simulation in step S3, fluid detection is performed on the fractures and microfractures, and local mesh encryption is performed on the fractures and microfractures to simulate the stress concentration factor distribution and establish a stress concentration factor distribution model.

[0027] The present invention is further configured such that step S5 specifically combines the stress concentration degree prediction in the carbonate rock formation stress concentration coefficient distribution model with the seismic attributes and fluid detection results to perform fluid-solid coupling, identify the stress concentration distribution area, and use the common development area of ​​fluid and stress concentration as the high-pressure identification area.

[0028] For areas with large stress concentration and fluid distribution, comprehensive judgment is made on the existence of abnormally high pressure in carbonate formations.

[0029] It should be noted that the magnitude of stress concentration is determined by each research area, there is no unified standard, and each area has its own policy. That is to say, the pressure coefficient of the actual high-pressure well and normal-pressure well in area A is used to establish a relationship curve with the stress concentration coefficient of the well in the stress concentration body, and the boundary between normal and abnormal pressure is calculated. However, in area B, due to different acquisition parameters of the seismic data body, the data obtained are also different. Only the boundary value suitable for the stress concentration in area B and the actual drilling pressure system in area B can be formed. The application of the boundary value of area B in area A will cause large errors.

[0030] The present invention also provides a carbonate rock abnormal high pressure prediction system under the multi-physical field coupling effect, including an acquisition module, a model construction module, a calculation module, a simulation module and a fluid-solid coupling module;

[0031] Among them, the acquisition module is used to obtain various basic data of the strata in the study area;

[0032] The model construction module is used to detect stratum fractures, characterize energy attributes, and calculate curvature in the study area from a seismic perspective, and to perform structural modeling from a geological perspective;

[0033] The calculation module is used to carry out rock physics calculations, calculate various rock physical parameters of the formation, analyze fracture activity, simulate fracture mechanics damage, and calculate ground stress under the measured formation temperature conditions;

[0034] The simulation module is used for random simulation and fluid detection of carbonate rock formation fractures and microfractures, local mesh encryption at fractures and microfractures, and simulation of stress concentration factor distribution;

[0035] The fluid-solid coupling module is used to combine the stress concentration degree prediction in the carbonate rock formation stress concentration coefficient distribution model with the seismic attributes and fluid detection results to perform fluid-solid coupling, identify stress concentration distribution areas, and comprehensively determine the areas where abnormally high pressure exists in carbonate rock formations for areas where stress is concentrated and fluid is distributed.

[0036] In summary, the beneficial effects of the above technical solution of the present invention are as follows:

[0037] 1. The present invention improves the accuracy of prediction and forecasting of abnormally high pressure in oil and gas wells and the efficiency of safe drilling under complex geological conditions of carbonate rocks by simulating the changes in formation pore pressure under the multi-physical field fluid-solid coupling of carbonate formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0039] Figure 1 This is an overall flow chart of the method for predicting abnormally high pressure in carbonate rocks under the coupling of multiple physical fields described in the present invention.

[0040] Figure 2 This is a calculation flow chart of the method for predicting abnormally high pressure in carbonate rocks under the coupling of multiple physical fields described in the present invention.

[0041] Figure 3 Schematic diagram of fracture distribution in an embodiment of the present invention.

[0042] Figure 4 Schematic diagram of fracture activity analysis in an embodiment of the present invention.

[0043] Figure 5 Schematic diagram of stress concentration factor distribution in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings of the present invention. Based on the embodiments of the present invention, other similar embodiments obtained by ordinary technicians in the field without making any creative work should all fall within the scope of protection of the present invention.

[0045] In addition, the directional words mentioned in the following embodiments, such as "up", "down", "left", "right", etc., are only reference directions of the drawings. Therefore, the directional words used are used to illustrate rather than limit the invention.

[0046] The present invention will be further described below in conjunction with the accompanying drawings and preferred embodiments.

[0047] Embodiment 1:

[0048] like Figure 1-Figure 2 As shown in the figure, it is a preferred embodiment of the present invention, a method for predicting abnormally high pressure of carbonate rocks under the coupling of multiple physical fields, comprising the following steps:

[0049] S1: Obtain various basic data of the strata in the study area; the basic data include seismic data, structure, fracture, completion data, well logging, oil testing, and fluid PVT in the study area. The source of the seismic data is the seismic data body, including .sgy format files and .txt format files of structure, layer, and fracture data.

[0050] S2: From a seismic perspective, fracture detection, energy attribute characterization, and curvature calculation are performed; geological structure modeling is performed, and after exporting the model data, random fracture distribution calculation is performed using MATLAB+COMSOL, combined with actual drilling imaging logging, core fracture distribution, and seismic fracture detection results.

[0051] S21: Import the .sgy and horizon files of the seismic data volume of the study area into the seismic software for fracture coherence detection, energy attribute characterization and curvature calculation; the seismic software is Landmark DSG or Paradigm software for calculation;

[0052] S22: using the structure, layer, and fracture data to perform geological structure modeling, and exporting corresponding geological model data, and using MATLAB to perform random fracture calculations; the geological structure modeling is performed using any one of Petrel, SKUA-GOCAD, and JewelSuiteSubsurface Modeling software;

[0053] S23: Correct the fracture prediction model based on the actual drilling imaging logging data and core data, and generate a fracture file;

[0054] S24: Import the generated fracture file into COMSOL Multiphysics software for subsequent rock mechanics simulation under given multi-physics field conditions;

[0055] S25: The results of seismic software and geological model simulation are imported into Petrel, and compared and differentiated by combining actual drilling imaging logging and core fracture distribution to make the geological model close to the actual formation fracture state.

[0056] The results are as follows Figure 3 As shown, Figure 3 a represents the seismic coherence slice, Figure 3 b is the predicted crack density map, Figure 3 c is the curvature property map.

[0057] S3: Carry out rock physics calculations and rock mechanics simulations;

[0058] Based on the logging data, the mechanical parameters of the rock are obtained. Under the measured formation temperature conditions, rock mechanics simulation is performed based on the mechanical parameters, the activity analysis of simulated fractures and fracture mechanics damage simulation are performed, and the ground stress calculation is performed. The results are as follows: Figure 3 shown.

[0059] What step S3 mainly does is to perform rock mechanics simulation. First, rock physical calculations are performed, mainly based on logging data (AC, DEN, RD), to obtain the mechanical parameters of the rock, such as hardness, elastic modulus, Poisson's ratio, compressive strength, etc. With these parameters, rock mechanics simulation can be performed under given multi-physical field conditions to simulate the activity of the fracture, the damage of the fracture, etc. The principle of fracture activity is actually based on friction theory and the study of critical stress of faults under the Mohr-Coulomb criterion. Fault zone damage is to simulate damage in the simulation software, the rock reaches the cracking condition, the stress-strain relationship, and with the increase of force, the degree of rock fracture increases, and the expansion morphology and damage of the crack increase. The multi-physical conditions include temperature, pressure, stress and fluid flow.

[0060] Both the activity analysis of the fault and the fracture mechanics damage simulation reflect the activity and fragmentation of the fault zone. Before the tectonic stress on the fault is insufficient to cause shear failure, it is in a stable state. When sliding is reached, friction and movement begin to occur between the fault planes, which is the activity analysis of the fault. When the tectonic stress is large enough to cause stronger compression or displacement between the fault planes, there will be cracks and fragmentation between the fault and the structure, and between the faults, which is the so-called damage.

[0061] The ground stress can be calculated using the following formula:

[0062]

[0063]

[0064] Among them, σ h : minimum horizontal principal stress; σ H : maximum horizontal principal stress; σ v : total vertical stress; α vert : Effective stress coefficient in the vertical direction (Biot coefficient); α hor : Effective stress coefficient in the horizontal direction (Biot coefficient); μ: Static Poisson's ratio; P p : pore pressure; E: static Young's modulus; ξ h : Stress in the direction of minimum principal stress

[0065] Change; H : Strain in the direction of maximum principal stress.

[0066] S4: Based on the random simulation of carbonate rock formation fractures and microfractures and fluid detection, local mesh encryption is performed at fractures and microfractures to simulate the distribution of stress concentration factors; Figure 5 shown.

[0067] Based on the fracture activity analysis and fracture mechanics damage simulation in step S3, fluid detection is performed on fractures and microfractures, and local mesh encryption is performed on fractures and microfractures to simulate the stress concentration factor distribution and establish a stress concentration factor distribution model.

[0068] It should be noted that under the action of force, the stratum structure undergoes compression and tension, forming structures under different fault mechanisms, such as normal faults, strike-slip faults, reverse faults, etc. Under strong compression, the stratum deforms, forming stress concentration and forming some local closed spaces. If there are fluids (oil, gas, water) in these spaces, then in the limited closed space, under the action of compression, the fluids cannot be discharged, and high-pressure areas are easily formed. However, in the rock without fluid, that is, the so-called dry layer, although the rock is squeezed, it does not meet certain compression conditions, the rock will not burst, and there will be no high pressure. Therefore, fluid detection is required, and fluid detection can be done in seismic inversion, AVO and other attributes. Stress concentration means that the maximum stress at a certain point is divided by the nominal stress, and the ratio is always greater than 1. Stress concentration is a phenomenon in which stress increases significantly in a local area of ​​solid, and it often appears in sharp corners, holes, notches, grooves, and rigid constraints and their neighborhoods. In rock mass, it is manifested on both sides of the fracture and the fracture tip, as well as in some independent caves. Obtaining the stress concentration coefficient body is essentially the data body and nominal stress body of the maximum principal stress in geostress calculation, and performing body calculation to obtain the stress concentration coefficient. This can be done in software such as Petrel, SKUA-GOCAD, Comsol, Abaqus, etc.

[0069] S5: Comprehensively determine the areas where abnormally high pressure exists in carbonate formations.

[0070] Combined with the stress concentration degree prediction in the carbonate formation stress concentration coefficient distribution model, seismic attributes and fluid detection results, fluid-solid coupling is performed to identify the stress concentration distribution area, and the co-development area of ​​fluid and stress concentration is used as the high-pressure identification area. For areas with large stress concentration and fluid distribution, the carbonate formation abnormally high pressure area is comprehensively determined.

[0071] It should be noted that the magnitude of stress concentration is determined by each research area, there is no unified standard, and each area has its own policy. That is to say, the pressure coefficient of the actual drilled high-pressure well and normal-pressure well in area A is compared with the stress concentration coefficient of the well in the stress concentration body to establish a relationship curve, and the boundary between normal and abnormal pressure is obtained by the card value. However, in area B, due to the different acquisition parameters of the seismic data body, the data obtained are also different. Only the boundary value of the stress concentration suitable for area B and the actual drilling pressure system of area B can be formed. The application of the boundary value of area B in area A will cause a large error. Therefore, the area with large stress concentration in the present invention is the area in which the relationship curve between the pressure coefficient of the actual drilled high-pressure well and normal-pressure well and the stress concentration coefficient of the well in the stress concentration body is higher than the boundary between normal and abnormal pressure.

[0072] Embodiment 2:

[0073] The present invention also provides a carbonate rock abnormally high pressure prediction system under the multi-physical field coupling effect, which is applicable to the above-mentioned carbonate rock abnormally high pressure prediction method under the multi-physical field coupling effect, and includes an acquisition module, a model construction module, a calculation module, a simulation module and a fluid-solid coupling module;

[0074] Among them, the acquisition module is used to obtain various basic data of the strata in the study area;

[0075] The model construction module is used to detect stratum fractures, characterize energy attributes, and calculate curvature in the study area from a seismic perspective, and to perform structural modeling from a geological perspective;

[0076] The calculation module is used to carry out rock physics calculations, calculate various rock physical parameters of the formation, analyze fracture activity, simulate fracture mechanics damage, and calculate ground stress under the measured formation temperature conditions;

[0077] The simulation module is used for random simulation and fluid detection of carbonate rock formation fractures and microfractures, local mesh encryption at fractures and microfractures, and simulation of stress concentration factor distribution;

[0078] The fluid-solid coupling module is used to combine the stress concentration degree prediction in the carbonate rock formation stress concentration coefficient distribution model with the seismic attributes and fluid detection results to perform fluid-solid coupling, identify stress concentration distribution areas, and comprehensively determine the areas where abnormally high pressure exists in carbonate rock formations for areas where stress is concentrated and fluid is distributed.

[0079] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. Prediction method of abnormally high pressure in carbonate rocks under the coupling of multiple physical fields, It is characterized in that The following steps are involved: S1: Obtain basic data of the strata in the study area; S2: From the perspective of seismic, fracture detection, energy attribute characterization, and curvature calculation are performed; geological structure modeling is performed, and after exporting the model data, random fracture distribution calculation is performed using MATLAB+COMSOL, combined with real drilling imaging logging, core fracture distribution, and seismic fracture detection results. S3: Carry out rock physics calculations and rock mechanics simulations; S4: Based on the random simulation of fractures and microfractures in carbonate formations and fluid detection, local mesh encryption is performed at fractures and microfractures to simulate the distribution of stress concentration factors; S5: Comprehensively determine the areas where abnormally high pressure exists in carbonate formations.

2. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 1, It is characterized in that The basic data in step S1 include seismic data, structures, faults, completion data, well logging, oil testing, and fluid PVT of the study area.

3. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 2, It is characterized in that The seismic data source is a seismic data body, including .sgy format files and .txt format files of structure, stratigraphic and fracture data.

4. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 3, It is characterized in that Step S2 specifically includes the following steps: S21: Import the .sgy and horizon files of the seismic data volume in the study area into the seismic software for fracture coherence detection, energy attribute characterization and curvature calculation; S22: using the structure, layer, and fracture data to perform geological structure modeling, and deriving corresponding geological model data, and using MATLAB to perform random fracture calculations; S23: Correct the fracture prediction model based on the actual drilling imaging logging data and core data, and generate a fracture file; S24: Import the generated fracture file into COMSOL Multiphysics software to further refine the model for subsequent rock mechanics simulation under given multiphysics conditions; S25: The results of seismic software and geological model simulation are imported into Petrel, and compared and differentiated by combining actual drilling imaging logging and core fracture distribution to make the geological model close to the actual formation fracture state.

5. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 4, It is characterized in that The multi-physics conditions include temperature, pressure, stress, and fluid flow.

6. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 4, It is characterized in that The seismic software is Landmark DSG or Paradigm software for calculation.

7. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 4, It is characterized in that The geological structure modeling is carried out using any of the software including Petrel, SKUA-GOCAD, and JewelSuite Subsurface Modeling.

8. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 4, It is characterized in that Step S3 specifically includes obtaining the mechanical parameters of the rock based on the logging data, performing rock mechanics simulation based on the mechanical parameters under the measured formation temperature conditions, performing activity analysis of simulated fractures and fracture mechanics damage simulation, and calculating ground stress.

9. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 8, It is characterized in that Specifically, step S4 is to perform fluid detection on the fractures and microfractures based on the fracture activity analysis and fracture mechanics damage simulation in step S3, and to perform local mesh encryption on the fractures and microfractures to simulate the stress concentration factor distribution and establish a stress concentration factor distribution model.

10. The method for predicting abnormally high pressure of carbonate rocks under multi-physical field coupling according to claim 9, It is characterized in that Step S5 specifically includes combining the stress concentration degree prediction in the carbonate rock formation stress concentration coefficient distribution model with the seismic attributes and fluid detection results to perform fluid-solid coupling, identify the stress concentration distribution area, and use the common development area of ​​fluid and stress concentration as the high-pressure identification area.

11. A system for predicting abnormally high pressure of carbonate rocks under the effect of multi-physical field coupling, applicable to the method for predicting abnormally high pressure of carbonate rocks under the effect of multi-physical field coupling as claimed in any one of claims 1 to 10, It is characterized in that It includes acquisition module, model construction module, calculation module, simulation module and fluid-solid coupling module; Among them, the acquisition module is used to obtain various basic data of the strata in the study area; The model construction module is used to detect stratum fractures, characterize energy attributes, and calculate curvature in the study area from a seismic perspective, and to perform structural modeling from a geological perspective; The calculation module is used to carry out rock physics calculations, calculate various rock physical parameters of the formation, analyze fracture activity, simulate fracture mechanics damage, and calculate ground stress under the measured formation temperature conditions; The simulation module is used for random simulation and fluid detection of carbonate rock formation fractures and microfractures, local mesh encryption at fractures and microfractures, and simulation of stress concentration factor distribution; The fluid-solid coupling module is used to combine the stress concentration degree prediction in the carbonate rock formation stress concentration coefficient distribution model with the seismic attributes and fluid detection results to perform fluid-solid coupling, identify stress concentration distribution areas, and comprehensively determine the areas where abnormally high pressure exists in carbonate rock formations for areas where stress is concentrated and fluid is distributed.

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