CN-121980795-A - Oilfield well casing residual strength evaluation method and system based on numerical simulation

CN121980795ACN 121980795 ACN121980795 ACN 121980795ACN-121980795-A

Abstract

The invention provides a method and a system for evaluating the residual strength of an oilfield well casing based on numerical simulation, and relates to the technical field of oilfield development casing safety evaluation. The method comprises the steps of establishing a block scale fluid-solid coupling numerical model reflecting the coupling relation between injection and production dynamics and stratum mechanics response based on sleeve loss evaluation basic data of a target oilfield block to obtain ground stress field data of redistribution around a shaft, establishing a three-dimensional coupling mechanical model comprising stratum, cement rings and a sleeve by taking the ground stress field data of redistribution as boundary conditions and combining sleeve structure and material parameters, obtaining stress distribution and maximum equivalent stress of the sleeve under the action of injection and production load through numerical simulation, and carrying out residual strength evaluation and damage risk grading on the sleeve according to strength utilization rate and residual strength coefficient based on the maximum equivalent stress and yield strength of sleeve materials. Thereby improving the accuracy and dynamic prediction capability of the evaluation of the residual intensity of the oil field casing pipe and providing scientific decision basis for casing damage management.

Inventors

YE GUIGEN
HE YUCHEN
ZHU XIUXING

Assignees

中国石油大学(华东)

Dates

Publication Date: 20260505
Application Date: 20260123

Claims (10)

1. The method for evaluating the residual strength of the oilfield well casing based on numerical simulation is characterized by comprising the following steps of: Based on the sleeve loss evaluation basic data of the target oilfield block, establishing a block scale fluid-solid coupling numerical model reflecting the coupling relation between injection and production dynamics and stratum mechanics response, and simulating dynamic evolution of stratum pore pressure and a ground stress field in the long-term injection and production process to obtain the ground stress field data of redistribution around a shaft; Taking the redistributed ground stress field data as boundary conditions, combining the sleeve structure and material parameters, establishing a three-dimensional coupling mechanical model comprising stratum, cement sheath and sleeve, and obtaining the stress distribution and the maximum equivalent stress of the sleeve under the action of injection and production load through numerical simulation calculation; and based on the maximum equivalent stress and the yield strength of the sleeve material, carrying out residual strength evaluation and damage risk grading on the sleeve by adopting the strength utilization rate and the residual strength coefficient and combining the set safety coefficient.
2. The method for evaluating the residual strength of the oilfield well casing based on numerical simulation according to claim 1, wherein the casing damage evaluation basic data comprises block basic geological data, well pattern and well position data, injection and production engineering parameters, casing basic data and casing damage historical data.
3. The method for evaluating the residual strength of the oilfield well casing based on numerical simulation according to claim 2, wherein the establishing of the block scale fluid-solid coupling numerical model reflecting the coupling relation between injection and production dynamics and formation mechanical response simulates dynamic evolution of formation pore pressure and a ground stress field in a long-term injection and production process to obtain the data of the ground stress field with redistribution around the wellbore specifically comprises the following steps: constructing a finite element model covering the geological structure, well pattern distribution and non-uniform permeability characteristics of the target block based on the casing damage evaluation basic data; Setting a model mechanical boundary condition according to the ground stress field parameter, and setting a fluid flow boundary condition based on the injection and production engineering parameter; performing transient fluid-solid coupling numerical simulation, and calculating the distribution of formation pore pressure and a ground stress field after long-term injection and production; and extracting data of a redistributed ground stress field containing the sizes and directions of three main stresses at the end of a simulation period of the position of each target shaft, wherein the main stresses comprise a maximum horizontal main stress, a minimum horizontal main stress and a vertical main stress.
4. The method for evaluating the residual strength of the oilfield well casing based on numerical simulation as claimed in claim 1, wherein the method for evaluating the residual strength of the oilfield well casing based on numerical simulation is characterized in that the stress distribution and the maximum equivalent stress of the casing under the action of injection and production load are obtained by taking the redistributed ground stress field data as boundary conditions and combining the casing structure and material parameters to build a three-dimensional coupling mechanical model comprising stratum, cement ring and casing through numerical simulation calculation, and specifically comprises the following steps: Establishing a stratum-cement sheath-sheath three-dimensional entity finite element model according to sheath basic data; converting the redistributed ground stress field data into pressure load and applying the pressure load to the corresponding direction of the outer boundary of the model stratum; Applying a corresponding fluid pressure to the inner wall of the casing according to the production state of the well; setting displacement constraint on the model and endowing each component with material properties according to the sleeve loss evaluation basic data; and executing statics numerical simulation, and solving to obtain a stress cloud picture, a deformation state and a maximum equivalent stress value of the sleeve.
5. The method for evaluating the residual strength of the oilfield well casing based on numerical simulation according to claim 1, wherein the method for evaluating the residual strength and grading the damage risk of the casing based on the maximum equivalent stress and the yield strength of the casing material by adopting the strength utilization rate and the residual strength coefficient in combination with the set safety coefficient specifically comprises the following steps: Calculating the strength utilization rate of the sleeve based on the ratio of the maximum equivalent stress to the yield strength, and calculating the residual strength coefficient of the sleeve based on the ratio of the yield strength to the maximum equivalent stress; Comparing the intensity utilization rate and the residual intensity coefficient with preset safety coefficients, and judging sleeve loss if the intensity utilization rate is greater than or equal to 100% and the residual intensity coefficient is less than or equal to 1; otherwise, the risk states of different grades are classified according to the proximity degree of the residual intensity coefficient and the safety coefficient.
6. An oilfield well casing residual strength evaluation system based on numerical simulation, comprising: The injection and production simulation module is configured to establish a block scale flow-solid coupling numerical model reflecting the coupling relation between injection and production dynamics and stratum mechanics response based on the casing damage evaluation basic data of the target oilfield block, simulate the dynamic evolution of stratum pore pressure and a ground stress field in the long-term injection and production process, and obtain the ground stress field data of redistribution around a shaft; The stress analysis module is configured to establish a three-dimensional coupling mechanical model comprising a stratum, a cement ring and a sleeve by taking the redistributed ground stress field data as boundary conditions and combining the sleeve structure and material parameters, and obtain the stress distribution and the maximum equivalent stress of the sleeve under the action of injection and production load through numerical simulation calculation; The strength evaluation module is configured to evaluate the residual strength and grade the damage risk of the sleeve by adopting the strength utilization rate and the residual strength coefficient and combining the set safety coefficient based on the maximum equivalent stress and the yield strength of the sleeve material.
7. The oilfield well casing residual strength evaluation system based on numerical simulation of claim 6, wherein the casing damage evaluation base data comprises block base geological data, well pattern and well location data, injection and production engineering parameters, casing base data, and casing damage history data.
8. The oilfield well casing residual strength evaluation system based on numerical simulation according to claim 7, wherein the establishing of the block scale fluid-solid coupling numerical model reflecting the coupling relation between injection and production dynamics and formation mechanical response simulates dynamic evolution of formation pore pressure and a ground stress field in a long-term injection and production process to obtain the ground stress field data of redistribution around a well shaft, specifically comprises: constructing a finite element model covering the geological structure, well pattern distribution and non-uniform permeability characteristics of the target block based on the casing damage evaluation basic data; Setting a model mechanical boundary condition according to the ground stress field parameter, and setting a fluid flow boundary condition based on the injection and production engineering parameter; performing transient fluid-solid coupling numerical simulation, and calculating the distribution of formation pore pressure and a ground stress field after long-term injection and production; and extracting data of a redistributed ground stress field containing the sizes and directions of three main stresses at the end of a simulation period of the position of each target shaft, wherein the main stresses comprise a maximum horizontal main stress, a minimum horizontal main stress and a vertical main stress.
9. A computer readable storage medium having stored thereon a computer program, wherein the program when executed by a processor implements the steps of a method for evaluating the residual strength of an oilfield well casing based on numerical simulation as defined in any one of claims 1-5.
10. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor, when executing the program, performs the steps of a method for evaluating the residual strength of an oilfield well casing based on numerical simulation as claimed in any one of claims 1 to 5.

Description

Oilfield well casing residual strength evaluation method and system based on numerical simulation Technical Field The invention relates to the technical field of oilfield development casing safety evaluation, in particular to a numerical simulation-based oilfield well casing residual strength evaluation method and system. Background The large oil fields in the current world have the characteristics of multiple oil reservoir types, complex structure, wide buried depth distribution and the like. In the development process of oil fields, the problems of difficult formation energy replenishment, no injection and no production of water-flooding low-permeability reservoirs are quite common, and the pressure flooding and fracturing technology is an effective method for solving the development problem, and is an effective method for inducing the generation and expansion of a reservoir fracture network under the condition of exceeding the fracture pressure or near fracture pressure of the formations, and the oil displacement is realized by pushing an oil well through the injection of water into the formations with large displacement. However, in the old well pressure driving and fracturing operation of low-permeability oil reservoirs, the problem of casing damage is increasingly remarkable, casing damage can lead to injection and production failure of oil field blocks, yield reduction and even borehole rejection, and the safety production and development benefits of the oil field are seriously affected. Meanwhile, the problem of casing damage of an oil well is a geological engineering problem with multiple influencing factors and complex mechanisms, and casing damage is often the result of combined action of multiple factors, and relates to engineering factors such as water injection pressure and corrosion defects, and geological factors such as ground stress change and fault slippage. Therefore, the research on the evaluation model and the evaluation method for the residual intensity of the sleeve in the injection and production process has important significance for the sleeve damage prevention, control and treatment of the oil field. At present, the sleeve residual strength evaluation technology has the obvious defects that firstly, an evaluation mode is static, an empirical formula is relied on, static strength is checked or locally detected, the evaluation method lacks systematicness, dynamic property and predictability, the safety state and residual service life of the sleeve in the injection and production process are difficult to evaluate accurately, secondly, in the aspect of finite element technology, although individual researches adopt a numerical simulation method to analyze the stress of the sleeve, the technology is limited to a single well or a simplified model, the influence of multi-factor coupling such as integral stress field evolution, multi-well synergistic effect, crack/fault sliding and corrosion defect of block injection and production is not considered, the evaluation result and engineering actual deviation are larger, and a closed loop technology system from mechanism analysis and dynamic simulation to safety evaluation cannot be formed. Disclosure of Invention In order to solve the problems, the invention provides the evaluation method and the system for the residual strength of the oilfield well casing based on numerical simulation, which finish the transition from static analysis to dynamic prediction and from casing damage result evaluation to risk early warning of the residual strength evaluation of the casing, can accurately evaluate the current safety state of the in-service casing, and can further predict the casing damage risk evolution of the oil well under different production scenes. In order to achieve the above purpose, the present invention adopts the following technical scheme: In a first aspect, the invention provides a method for evaluating the residual strength of an oilfield well casing based on numerical simulation, which comprises the following steps: Based on the sleeve loss evaluation basic data of the target oilfield block, establishing a block scale fluid-solid coupling numerical model reflecting the coupling relation between injection and production dynamics and stratum mechanics response, and simulating dynamic evolution of stratum pore pressure and a ground stress field in the long-term injection and production process to obtain the ground stress field data of redistribution around a shaft; Taking the redistributed ground stress field data as boundary conditions, combining the sleeve structure and material parameters, establishing a three-dimensional coupling mechanical model comprising stratum, cement sheath and sleeve, and obtaining the stress distribution and the maximum equivalent stress of the sleeve under the action of injection and production load through numerical simulation calculation; and based on the maximum equivalent stress and the yield strength