CN-117251899-B - Fracturing parameter optimization method for improving transformation effect of tight sandstone reservoir

CN117251899BCN 117251899 BCN117251899 BCN 117251899BCN-117251899-B

Abstract

The invention discloses a fracturing parameter optimization method for improving the transformation effect of a tight sandstone reservoir, which comprises the steps of S1-S5, selecting a target well to be constructed, collecting geomechanical parameters of the tight sandstone reservoir in the target well and establishing a tight sandstone reservoir model in the target well, after the tight sandstone reservoir model is established, sequentially setting perforation parameters and construction parameters in the tight sandstone reservoir model, carrying out numerical simulation of hydraulic fracturing on the tight sandstone reservoir model in the target well by utilizing a three-dimensional discrete lattice method to obtain the fracturing parameter, finally comparing and analyzing each numerical simulation result, screening out an optimal scheme, evaluating and obtaining the numerical value of hydraulic fracturing of the tight sandstone reservoir on site by establishing the construction parameters of the tight sandstone reservoir model, and grasping the data of a stratum and the condition of the evaluation construction process according to the evaluated and obtained numerical value of hydraulic fracturing of the tight sandstone reservoir on site.

Inventors

TANG BOTAO
FAN YU
LI LI
CHEN WEIHUA
ZENG JI
LI JINSUI
WANG JINXI

Assignees

中国石油天然气股份有限公司

Dates

Publication Date: 20260512
Application Date: 20220610

Claims (10)

1. The fracturing parameter optimization method for improving the reconstruction effect of the tight sandstone reservoir is characterized by comprising the following steps of: s1, selecting a target well to be constructed, collecting geomechanical parameters of a tight sandstone reservoir in the target well and establishing a tight sandstone reservoir model in the target well, wherein the geomechanical parameters comprise model geometric dimensions, ground stress difference values, rock elastic modulus and Poisson' S ratio; s2, setting perforation parameters of a compact sandstone reservoir model in a target well, wherein the perforation parameters comprise a plurality of holes, aperture size, phase angle size, perforation arrangement mode and interval among multiple clusters of perforations; S3, setting construction parameters of a tight sandstone reservoir model in the target well, wherein the construction parameters comprise pumping displacement, pumping duration, fracturing fluid viscosity and fracturing fluid density; S4, performing numerical simulation of hydraulic fracturing on the compact sandstone reservoir model in the target well by using a three-dimensional discrete lattice method, and obtaining numerical simulation results of the hydraulic fracturing of each perforation parameter and construction parameter according to geomechanical parameters of the reservoir model in the target well, wherein the numerical simulation of the hydraulic fracturing also has stratum fracture pressure values and geometric forms of cracks; s5, comparing and analyzing each simulation result, and screening out an optimal scheme.
2. A fracturing parameter optimization method for improving the effectiveness of tight sandstone reservoir modification according to claim 1, wherein in said step S4, said three-dimensional discrete lattice method is to use a bonded particle model to simplify rock particles into nodes and said nodes are spring-connected to represent rock contact surfaces with elastic characteristics, and a smooth joint surface model to simulate pre-stored discontinuous weaknesses in the initial cluster of perforations or rock body.
3. The fracturing parameter optimization method for improving the reconstruction effect of the tight sandstone reservoir according to claim 2, wherein the nodes are connected with the springs, and a pipe network for fluid to flow is formed among coin-shaped fluid units positioned in the center of the broken springs.
4. The fracturing parameter optimization method for improving the reconstruction effect of a tight sandstone reservoir according to claim 3, wherein the three-dimensional discrete lattice method has a mechanical model process, and the corresponding relationship between the tensile shear failure strength of the spring and the rock particles in the mechanical model process of hydraulic fracturing is as shown in the following formula (1): (1) In the formula, F Nmax and F Smax respectively represent the breaking tension and breaking shearing force of the spring, a t is a tensile strength correction coefficient, T and C respectively represent the tensile strength and shearing strength of the macroscopic rock mass, R represents the size of a grid cell, mu represents a friction coefficient, and a s is a shearing strength correction coefficient.
5. The fracturing parameter optimization method for improving the reconstruction effect of a tight sandstone reservoir according to claim 3, wherein the three-dimensional discrete lattice method is provided with a fluid flow model process, and in the fluid flow model process of hydraulic fracturing, the pipe width and the pipe length of a water pipe are set to be equal, and a flow formula (2) of a water body from a water body unit A to a water body unit B along the water pipe is as follows: Wherein k r ＝s 2 (3-2 s) (2) Q represents fluid flow, beta is a dimensionless coefficient, k r represents relative permeability, a represents crack width, mu represents fluid viscosity, P A and P B respectively represent water pressure at the nodes A and B, rho w represents fluid density, g represents gravitational acceleration, z A and z B respectively represent elevation at the nodes A and B, and s represents water saturation; The calculation method is used for solving the flow of the fluid flow q with time change in the water body flowing process q i , and in the flowing time step Deltat f , the flow pressure increment is DeltaP, and a calculation formula (3) of DeltaP is as follows: (3) In the formula: The expression shows the fluid elastic modulus, V is the volume of the node, and since the flow rate equal to the pipe length is a constant value, V represents the total flow rate of all the nodes connected with the water pipe.
6. A fracturing parameter optimization method for improving the reconstruction effect of a tight sandstone reservoir according to claim 3, wherein the three-dimensional discrete lattice method has a fluid-solid coupling process, the fluid-solid coupling process of hydraulic fracturing adopts a fluid-solid coupling method of mechanically incompressible fluid to perform stress generated by injecting water into the rock of the tight sandstone reservoir to fracture the rock or form coupling of pre-stored joints in the rock mass and rock deformation, the fluid-solid coupling solves the crack permeability through the rock deformation and the initial crack width, and the fluid-solid coupling is influenced by the permeability, the water pressure acts on the surface of the crack to influence the rock deformation, and the deformation of the rock in turn causes the change of the crack width and the water pressure, thereby causing the change of the crack permeability.
7. The fracturing parameter optimization method for improving the transformation effect of the tight sandstone reservoir according to claim 6, wherein the fracturing pressure of the tight sandstone reservoir rock by using the fluid-solid coupling method is directly obtained from a numerical simulation result, and the fracture geometry is used for solving the perforation initiation efficiency and the transformation volume of each cluster of tight sandstone reservoir fractures; the perforation initiation efficiency is calculated as shown in the formula (4): (4) In the formula (i), The crack volume of the ith crack is the total number of the single-section cracks, For the fracture volume of the jth cluster of fractures, a perforation cluster is an effective perforation cluster when the fracture volume of the perforation cluster is greater than the ideal fracture volume, i.e., the total fracture volume divided by the number of fracture clusters is greater than 70%.
8. The fracturing parameter optimization method for improving the reconstruction effect of the tight sandstone reservoir according to claim 7, wherein the calculation formula (5) of the reconstruction volume of each cluster of tight sandstone reservoir cracks is as follows: Wherein, the (5) In the formula, S V is the standard deviation of the normalized reservoir reformation volume, Is the average value of the transformation volume of each cluster of fracture normalized reservoir, Is the reservoir retrofit volume of the ith cluster.
9. The fracturing parameter optimization method for improving the reconstruction effect of a tight sandstone reservoir according to claim 1, wherein in the step S1, the length, width and height of the model geometry of the tight sandstone reservoir model are 300m×80m×30m.
10. The fracturing parameter optimization method for improving the reconstruction effect of a tight sandstone reservoir according to claim 1, wherein in the step S1, the ground stress difference value is obtained by performing on-site ground stress measurement according to the tight sandstone reservoir in the target well, and the rock elastic modulus and poisson ratio of the tight sandstone reservoir are obtained by on-site coring and rock mechanical test.

Description

Fracturing parameter optimization method for improving transformation effect of tight sandstone reservoir Technical Field The invention relates to the technical field of oil and gas development, in particular to a fracturing parameter optimization method for improving the transformation effect of a tight sandstone reservoir, which is used for optimizing the fracturing construction of efficient initiation and uniform expansion of multiple clusters of cracks of a horizontal well. Background The dense sandstone gas is natural gas distributed in the dense sandstone and is sometimes classified as unconventional natural gas, the reservoir rock where the dense sandstone gas is positioned has low porosity, low permeability, low gas saturation and high water saturation, the natural gas flows slowly in the sandstone layer, the exploitation of the dense sandstone gas in the sandstone layer needs to adopt a fracturing technology, the exploitation cost is high, For the natural cracks of the dense sandstone reservoir of the Qilin block sand-Rabdosia temple group in the middle area of the Sichuan basin, the reservoir heterogeneity of the dense sandstone reservoir is strong, and the volume of the dense sandstone reservoir is improved by adopting a horizontal well sectional multi-cluster perforation and high-strength sand-adding fracturing technology in the early stage of exploitation. After on-site fracturing construction, wide area electromagnetic method monitoring shows that the crack extension between partial horizontal well clusters is unbalanced, and perforation cracking efficiency is low, so that optimal design of perforation parameters and construction parameters is urgently needed for the compact sandstone reservoir of the block, the cracking pressure of perforation cracking is effectively reduced, the crack cracking is controlled, the perforation cracking efficiency is improved, the uniform extension of multi-cluster cracks is promoted, and the transformation volume of the reservoir is improved to the maximum extent. Disclosure of Invention The invention aims to solve the technical problems that after multi-cluster perforation and high-strength sand fracturing construction, a tight sandstone layer causes uneven crack expansion among well clusters, low perforation efficiency and high fracturing pressure after the cracks are fractured. The invention is realized by the following technical scheme: A fracturing parameter optimization method for improving the reconstruction effect of a tight sandstone reservoir comprises the following steps: s1, selecting a target well to be constructed, collecting geomechanical parameters of a tight sandstone reservoir in the target well and establishing a tight sandstone reservoir model in the target well, wherein the geomechanical parameters comprise model geometric dimensions, ground stress difference values, rock elastic modulus and Poisson' S ratio; s2, setting perforation parameters of a compact sandstone reservoir model in a target well, wherein the perforation parameters comprise a plurality of holes, aperture size, phase angle size, perforation arrangement mode and interval among multiple clusters of perforations; S3, setting construction parameters of a tight sandstone reservoir model in the target well, wherein the construction parameters comprise pumping displacement, pumping duration, fracturing fluid viscosity and fracturing fluid density; S4, carrying out numerical simulation of hydraulic fracturing on a reservoir model in the target well by using a three-dimensional discrete lattice method, and obtaining numerical simulation results of the hydraulic fracturing of each perforation parameter and construction parameter according to geomechanical parameters of the reservoir model in the target well, wherein the numerical simulation of the hydraulic fracturing also has stratum fracture pressure values and geometric forms of cracks; s5, comparing and analyzing each simulation result, and screening out an optimal scheme. Wherein in the step S4, the three-dimensional discrete lattice method is to use a bonded particle model to simplify rock particles into nodes and the nodes represent rock contact surfaces with elastic characteristics through spring connection, and a smooth joint surface model is used for simulating initial clusters of perforation or discontinuous weak surfaces prestored in a rock body. The nodes are connected with the springs with normal rigidity and shearing rigidity, the tension shearing of the springs corresponds to the tension shearing damage of rock particles, a pipe network can be formed among coin-shaped fluid units positioned in the center of the broken springs for fluid to flow, a plurality of quasi-random distribution nodes connected with the springs form a node spring network, and the nodes can be placed in any direction to accurately and efficiently represent fracture. The three-dimensional discrete lattice method is provided with a mechanical mode