A Fluid-Solid-Heat Coupling Simulation Method for the Progressive Collapse Process of the Borehole Wall in Heterogeneous Formation

Abstract

The invention discloses a fluid-solid-thermal coupling simulation method for the gradual collapse process of a well wall in a heterogeneous formation, including determining formation stress, pore pressure, and wellbore pressure; determining the number of samples of rock mechanics parameters, rock foundation physical property parameters, and rock mechanics parameters; determine the optimal distribution function of each parameter and the corresponding characteristic parameters; establish a fluid-solid-thermal coupling finite element mathematical model of the stress distribution around the well; calculate the stress distribution around the well; calculate the damage variable F; the damage variable F determines the damage area; repeat steps to iterate until the damage variable F≤0, draw the wall instability area map, and determine the NYZA value at each iteration step. The present invention uses the uncertainty of the input parameters to represent the heterogeneity of the rock mechanical parameters; adopts the continuous damage theory, changes the mechanical parameters of the damaged area, regards the area as being equivalently excavated, and simulates the progressive failure development of the shaft wall four stages: crack initiation, propagation, avalanche formation and stabilization.

Description

technical field [0001] The invention relates to a fluid-solid-thermal coupling simulation method for the progressive collapse process of a well wall in a heterogeneous formation, and belongs to the fields of petroleum drilling engineering, rock mechanics and engineering. Background technique [0002] Drilling the formation to form a wellbore will destroy the original stress balance, resulting in stress concentration on the wellbore wall, and the drilling fluid pressure is not enough to support the wellbore confining pressure, resulting in wellbore instability. Borehole instability is a gradual process. Initially, the circular wellbore gradually expands and destroys in the direction of the minimum principal stress, thereby releasing the stress concentration. If the damage degree is low and the drilling operation can be maintained normally, it is called borehole wall collapse; if the damage degree is high, it is called borehole wall collapse. Zoback pointed out that the direc...

AI Technical Summary

Problems solved by technology

In addition, the existing numerical simulations of progressive failure of wellbore walls (finite element method, discrete element method and boundary element method) only consider the deformation and failure characteristics of rock materials, ignoring the influence of fluid-solid-thermal multi-field coupling

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