Prediction method for fracture pressure of well wall of coal seam directional well

Abstract

The invention relates to a prediction method for fracture pressure of the well wall of a coal seam directional well. The prediction method specifically comprises the steps that 1, the ground stress magnitude, the stratum pore pressure magnitude, the coal and rock tensile strength and the like are tested; 2, transforming is conducted among a borehole coordinate system, an in-situ stress coordinatesystem and a geodetic coordinate system, and the in-situ stress is transformed into the borehole coordinate system for force analysis; 3, according to a stress calculation model of the well wall of the coal and rock stratum directional well, the stress distribution conditions around the well wall of the coal and rock stratum directional well are calculated; 4, the fracture pressure when a coal androck body on the well wall of the coal and rock stratum directional well is subjected to a tensile failure is calculated; 5, the fracture pressure when a coal and rock cleat intersecting with the well wall of the coal and rock stratum directional well is subjected to a tensile failure or a shear failure is calculated; 6, the fracture pressure when a coal and rock cleat not intersecting with the well wall of the coal and rock stratum directional well is subjected to a shear failure is calculated; and 7, the fracture pressure of the well wall of the coal and rock stratum directional well is theminimum value of all the fracture pressures under different fracture modes. According to the prediction method, the prediction result of the fracture pressure of the well wall is more realistic and reliable.

Description

technical field [0001] The invention relates to the drilling and completion technology of coal bed gas wells, in particular to a method for predicting the wall fracture pressure of coal seam directional wells. Background technique [0002] Coalbed methane is an important unconventional oil and gas resource, and its development and utilization have attracted more and more attention and attention from all over the world. my country's coalbed methane reserves are abundant, as high as 36.8×10 12 m 3 , is the country with the third largest coalbed methane reserves in the world after Russia and Canada. If coalbed methane resources can be developed efficiently, it will be of great significance to my country's energy supply. The main component of coalbed methane is methane. When its air concentration reaches 5% to 16%, it will explode when exposed to open flames. This is also the root cause of coal mine gas explosion accidents. In addition, if the coalbed methane is directly dis...

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Problems solved by technology

[0011] The purpose of the present invention is to provide coal seam directional well wall fracture pressure prediction method, this coal seam directional well wall fracture pressure prediction method is used to solve existing coal seam directional well wall fracture pressure prediction method in calculating and predicting coal seam directional well well There are varying degrees of inapplicability problems at all wall rupture pressures

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