CN-122021160-A - Geological model-based design method for three-dimensional well pattern and seam pattern of coal bed gas fracturing

CN122021160ACN 122021160 ACN122021160 ACN 122021160ACN-122021160-A

Abstract

The invention relates to the technical field of geologic model analysis, in particular to a design method of a coal bed methane fracturing three-dimensional well pattern network based on a geologic model; the method comprises the steps of carrying out low potential gradient optimizing calculation by utilizing a field to obtain a shaft space topological coordinate avoiding a high potential area so as to reduce the risk of well wall instability, simultaneously utilizing an equipotential surface threshold value cutoff fracture extension simulation in the field to accurately determine hydraulic fracture geometric form parameters matched with stratum energy constraint, finally integrating the parameters to generate an optimized three-dimensional well pattern design scheme, and realizing efficient and safe fracturing design based on rock mass accumulated deformation energy distribution characteristics.

Inventors

HUANG HAOPING
HOU LI
ZHANG GUOQI
Hou pan
GAO YANG
FU CHAO
Gan Xinke
SHI YONGXIANG
YAO XIAOQIANG
WEN LIJUAN
FENG XIN

Assignees

新疆亚新煤层气勘探开发有限责任公司

Dates

Publication Date: 20260512
Application Date: 20260129

Claims (10)

1. The design method of the three-dimensional well pattern for fracturing the coalbed methane based on the geological model is characterized by comprising the following steps of: S1, acquiring rock mechanical attribute data of a target coal seam area, and constructing a three-dimensional discrete geological model containing grid node mechanical parameters; S2, calculating stress states and accumulated deformation energy of each grid node based on grid node mechanical parameters in the three-dimensional discrete geological model, and generating a three-dimensional dynamic induced stress potential energy tensor field; S3, performing low potential energy gradient optimizing calculation by using the three-dimensional dynamic induced stress potential energy tensor field as a path planning space, and generating a shaft space topological coordinate avoiding a high potential energy area; S4, taking the space topological coordinate of the shaft as a starting point, performing crack extension simulation in the three-dimensional dynamic induced stress potential energy tensor field, and determining geometrical form parameters of the hydraulic crack by using the equipotential surface threshold value cutoff crack extension calculation in the field; s5, generating a three-dimensional well pattern design scheme according to the well bore space topological coordinate and the hydraulic fracture geometric form parameter.
2. The geological model-based coal bed methane fracturing three-dimensional well pattern design method is characterized in that the rock mechanical property data acquisition process specifically comprises the following steps: performing geophysical well logging operation and core drilling operation on a target coal seam area, acquiring longitudinal wave time difference, transverse wave time difference and logging density of the target coal seam area through geophysical well logging, and performing rock mechanical testing in a laboratory by utilizing a drilled core to determine static Young modulus, static Poisson's ratio and uniaxial compressive strength parameters of the rock; Calculating rock dynamic mechanical parameters according to the longitudinal wave time difference, the transverse wave time difference and the logging density, and establishing a regression conversion equation by utilizing the measured static Young modulus, static Poisson ratio and uniaxial compressive strength parameters and the calculated rock dynamic mechanical parameters; And correcting the calculated rock dynamic mechanical parameters into static rock mechanical parameters by using the regression conversion equation to obtain rock mechanical attribute data of the target coal seam area which is continuously distributed in the depth direction.
3. The geological model-based coalbed methane fracturing three-dimensional well pattern design method is characterized in that the construction process of the three-dimensional discrete geological model specifically comprises the following steps: determining the space geometric positions of a coal seam roof, a coal seam floor and faults by utilizing seismic structure interpretation data of a target coal seam area, and establishing a closed three-dimensional geological structure frame; Discretizing the three-dimensional geological structure frame in a three-dimensional space to generate a three-dimensional space grid system formed by hexahedral units, and determining the space coordinates of each grid node in the three-dimensional space grid system; And mapping the rock mechanical attribute data of the target coal seam region into a three-dimensional space grid system by adopting a Kriging interpolation algorithm, endowing each grid node with a corresponding grid node mechanical parameter through interpolation calculation, and constructing a three-dimensional discrete geological model containing the grid node mechanical parameters.
4. The geological model-based coalbed methane fracturing three-dimensional well pattern design method is characterized in that the generation process of the three-dimensional dynamic induced stress potential energy tensor field specifically comprises the following steps: Applying a vertical overburden formation pressure load, a horizontal maximum horizontal principal stress load and a horizontal minimum horizontal principal stress load to the three-dimensional discrete geological model as boundary conditions; Establishing an overall stiffness matrix by using a finite element numerical simulation algorithm and utilizing grid node mechanical parameters, solving a balance equation, and calculating to obtain displacement vectors of all grid nodes; calculating strain tensors by utilizing a geometric equation according to displacement vectors of all grid nodes, and calculating three-dimensional principal stress tensors of all grid nodes by combining a physical constitutive equation so as to determine stress states of all grid nodes; substituting the stress state and the strain tensor of each grid node into an elastic strain energy density formula to calculate the accumulated deformation energy of each grid node; And assigning the stress state and the accumulated deformation energy of each grid node to the corresponding grid node as tensor attributes, and generating a three-dimensional dynamic induced stress potential energy tensor field.
5. The geological model-based coalbed methane fracturing three-dimensional well pattern design method is characterized in that the generation process of the shaft space topological coordinate specifically comprises the following steps: Setting a wellhead initial node and a well bottom target node in the three-dimensional dynamic induced stress potential energy tensor field; Extracting accumulated deformation energy values of all grid nodes in the three-dimensional dynamic induced stress potential energy tensor field to construct a potential energy scalar field, and calculating the spatial change rate of the accumulated deformation energy values between adjacent grid nodes in the potential energy scalar field to determine a potential energy gradient vector; marking grid nodes with accumulated deformation energy values exceeding a preset stratum stability threshold as high potential energy areas and setting the high potential energy areas as path planning barrier points; Taking a wellhead starting node as a starting point and a well bottom target node as an end point, adopting a minimum gradient path searching algorithm to perform iterative optimization in a grid node set of a non-high potential energy area, and screening out a connected grid node sequence with the smallest sum of along-the-way potential energy gradient vector modulus; and sequentially extracting the space coordinates of each grid node in the connected grid node sequence to generate a shaft space topological coordinate avoiding a high potential energy area.
6. The geological model-based coal bed methane fracturing three-dimensional well pattern design method is characterized in that the determining process of the geometric form parameters of the hydraulic fracture specifically comprises the following steps: determining a plurality of discrete nodes from the wellbore space topological coordinates as initiation source points; determining the dominant extension direction of the crack vertical to the minimum horizontal main stress according to the stress tensor attribute of each grid node in the three-dimensional dynamic induced stress potential energy tensor field; Adopting a grid node tracking algorithm to perform iterative computation to adjacent grid nodes on the outer layer by taking the cracking source point as a center so as to simulate the expansion process of cracks in a three-dimensional space; setting an equipotential surface threshold value for representing a crack stop expansion energy boundary, and identifying a space equipotential surface with an accumulated deformation energy value equal to the equipotential surface threshold value in the three-dimensional dynamic induced stress potential energy tensor field; monitoring the position of a crack tip in real time in the iterative calculation process of crack extension simulation, and immediately cutting off crack extension calculation when the crack tip touches the space equipotential surface; And extracting a space coordinate set of all grid nodes penetrated by the crack propagation path, calculating the length value, the height value and the width value of the crack according to the space coordinate set, and determining the geometric form parameters of the hydraulic crack.
7. The geological model-based coal bed methane fracturing three-dimensional well pattern design method is characterized in that the generation process of the three-dimensional well pattern design scheme specifically comprises the following steps: adopting a cubic spline interpolation algorithm to carry out smooth fitting treatment on the space topological coordinates of the shaft to generate a continuous three-dimensional shaft track curve; Calculating well inclination angle values and azimuth angle values of the three-dimensional well bore track curve at different depth positions; planning fracturing staged positions and perforation cluster positions on the three-dimensional wellbore track curve according to the geometric form parameters of the hydraulic fracture; constructing a virtual hydraulic fracture grid model distributed along the three-dimensional wellbore trajectory curve according to the fracturing segmentation position, the perforation cluster position and the hydraulic fracture geometric form parameter; The three-dimensional wellbore trajectory curve and the virtual hydraulic fracture grid model are spatially combined to form a visualized three-dimensional engineering geological entity model; and outputting a three-dimensional well pattern design scheme comprising the well inclination angle value, the azimuth angle value, the fracturing segmentation position, the perforation cluster position and the virtual hydraulic fracture grid model data.
8. The method for designing the three-dimensional well pattern for fracturing the coalbed methane based on the geological model according to claim 2, wherein the regression conversion equation is a unitary linear regression equation established by utilizing the static mechanical parameters of the rock measured in a laboratory and the dynamic mechanical parameters of the rock obtained by calculation, and is used for correcting the dynamic mechanical parameters into the static mechanical parameters of the rock.
9. A method of designing a three-dimensional well pattern for fracturing coal bed gas based on a geologic model as defined in claim 3, wherein the three-dimensional space grid system is generated by discretizing the three-dimensional geologic structure frame by a hexahedral mesh subdivision algorithm, and the grid node mechanical parameters are obtained by mapping the rock mechanical property data to each grid node in the three-dimensional space grid system by a kriging interpolation algorithm.
10. The geological model-based design method of the three-dimensional well pattern for coal bed methane fracturing, according to claim 6, wherein the dominant extension direction of the fracture is determined by calculating the eigenvalue and eigenvector of the stress tensor at the point of origin, and the dominant extension direction of the fracture is perpendicular to the eigenvector direction corresponding to the minimum horizontal principal stress.

Description

Geological model-based design method for three-dimensional well pattern and seam pattern of coal bed gas fracturing Technical Field The invention relates to the technical field of geologic model analysis, in particular to a design method of a three-dimensional well pattern for fracturing coal bed gas based on a geologic model. Background In the field of exploration and development of unconventional oil and gas resources, particularly coal bed gas resource exploitation, hydraulic fracturing technology is an important means for improving reservoir permeability and improving single well productivity. Coal rock mass is used as sedimentary rock with unique cause, and has stronger heterogeneity and anisotropy, the internal pore structure is complex, and the stress distribution and mechanical properties in stratum are generally obviously different in three-dimensional space due to the influence of geological structure movement. The existing coalbed methane development well pattern and seam pattern design technology depends on geological structure interpretation data and conventional rock mechanical parameters, and the design emphasis generally tends to pursue geometric penetration degree of a shaft in a geological target point and transformation range of hydraulic cracks in volume. However, existing design methods often consider the formation as relatively homogeneous or only considering static stress media when planning wellbore trajectories, and may not be deep enough for quantitative analysis of deformation potential energy and local stress concentration states accumulated by the formation rock mass during complex geological histories. The situation can lead to the designed shaft track to pass through the area with higher accumulated deformation energy of the rock mass without knowledge, thereby increasing the risk of encountering complex engineering accidents such as instability, collapse or jamming of the drill in the drilling process. In addition, in the aspect of hydraulic fracture extension simulation, the prior art mostly adopts a geometric model based on fracture mechanics or a simplified extension criterion, and lacks sufficient physical mechanism consideration on how to restrict the dynamic extension boundary of the fracture in the potential energy state in the stratum, so that the prediction result of the fracture geometry sometimes has difficulty in accurately reflecting the practical limiting effect of stratum energy on the fracture extension. Therefore, a method capable of tightly combining formation stress potential energy distribution and well pattern design is discussed, and the method has important engineering application value for optimizing the coal bed methane development effect in a complex geological environment. Disclosure of Invention The invention aims to provide a design method of a three-dimensional well pattern for fracturing coal bed gas based on a geological model, so as to solve the problems in the background technology. The specific technical problems include how to utilize a three-dimensional dynamic induced stress potential energy tensor field constructed based on rock mechanical properties to carry out low potential energy gradient path planning and equipotential surface fracture cutoff calculation so as to solve the technical problems that a well bore track passes through a high potential energy instability risk area and the matching degree between a hydraulic fracture morphology prediction result and a stratum energy state is insufficient due to insufficient consideration of rock mass accumulated deformation energy distribution characteristics in the existing coal seam gas fracture design. In order to achieve the above purpose, the invention aims to provide a design method of a three-dimensional well pattern for fracturing coal bed gas based on a geological model, which specifically comprises the following steps: s1, acquiring rock mechanical property data of a target coal seam area, wherein the rock mechanical property data specifically comprises the following steps: performing geophysical well logging operation and core drilling operation on a target coal seam area, acquiring longitudinal wave time difference, transverse wave time difference and logging density of the target coal seam area through geophysical well logging, and performing rock mechanical testing in a laboratory by utilizing a drilled core to determine static Young modulus, static Poisson's ratio and uniaxial compressive strength parameters of the rock; Calculating rock dynamic mechanical parameters according to the longitudinal wave time difference, the transverse wave time difference and the logging density, and establishing a regression conversion equation by utilizing the measured static Young modulus, the static Poisson ratio and the uniaxial compressive strength parameters and the calculated rock dynamic mechanical parameters, wherein the regression conversion equation is a unitary linear regression eq