Method for determining fracture pressure of hydraulic fracturing on basis of geological strength index

Abstract

The invention discloses a method for determining fracture pressure of hydraulic fracturing on the basis of a geological strength index, which includes the steps of preparing a standard sample by utilizing an intact coal rock, performing tests for homotaxial and triaxial compression strength, determining a GSI (geological strength index) value of a reservoir according to a geological strength index template, and determining the fracture pressure of the reservoir according to structural characteristics of the intact coal rack and the reservoir which are comprehensively considered. Limitedness that tensile strength tested by the intact coal rock is taken as the tensile strength of the entire reservoir is avoided, structural characteristics of the reservoir are considered, the GSI value is determined according to a rock structure quantized GSI template and a coal structure quantized GSI template, and then the fracture pressure of the reservoir is determined. A new method for determining fracture pressure according to of strength of the intact coal rock and structural characteristics of the reservoir is realized, and the foundation for quick and easy determination for fracture pressure of the reservoir is laid.

Description

technical field [0001] The invention belongs to the technical field of hydraulic fracturing transformation of oil and gas reservoirs and coal seams, and in particular relates to a method for determining hydraulic fracturing fracture pressure based on geological strength indexes. Background technique [0002] As a technical measure for reservoir permeability enhancement, hydraulic fracturing has the characteristics of large permeability enhancement range and remarkable effect, and has been widely used in the fields of oil and gas field development and gas drainage. [0003] Fracture pressure is an important parameter for reservoir hydraulic fracturing. First, the tensile strength of the reservoir should be tested. The traditional method is to collect complete coal and rock blocks, then prepare standard samples in the room, and then test their tensile strength one by one, and take the average value, and then determine the fracture pressure of the reservoir according to the dep...

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Problems solved by technology

[0003] Fracture pressure is an important parameter for reservoir hydraulic fracturing. First, the tensile strength of the reservoir should be tested. The traditional method is to collect complete coal and rock blocks, then prepare standard samples in the room, and then test their tensile strength one by one, and take the average value, and then determine the fracture pressure of the reservoir according to the depth of the reservoir, the magnitude of the in-situ stress and the formation pressure, and this value represents the magnitude of the fracture pressure at a certain depth of the entire reservoir, without considering the structural characteristics of the reservoir

In fact, it is unscientific to use the tensile strength of the whole sample collected to represent the tensile strength of the entire reservoir, and there is a large error with the actual one. The structural characteristics of the reservoir seriously affect the tensile strength, and then affect the burst pressure

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