Cavitation‐Induced Shear Failure Mechanism of Fractured Plugging Zone and Structure Strengthening Method for Lost Circulation Control in High‐Temperature and High‐Pressure Fractured Gas Reservoirs

The stability of the plugging zone has a great impact on lost circulation control and gas invasion prevention in fractured reservoirs. In this work, the concept of “cavitation‐induced shear failure” is put forward based on the analysis of the flow field characteristics, and the failure mechanism is discussed. The strength physical model of a fractured plugging zone is formed based on the analysis of the characteristic parameters of LCMs and the failure mechanism. And then the simulation experiments of cavitation‐induced shear failure, gas invasion prevention, pressure bearing, and tight plugging are carried out. The research shows that (1) the fractured plugging zone is a dense granular matter system, and the contact forces and quid bridge force are dominant in its internal; (2) the cavitation‐induced shear failure is one of the main failure modes of the plugging zone in a fractured gas reservoir, and the failure process includes three steps: gas diffusion‐dilution damage, confluence and carry damage, and displacement dislocation shear failure; (3) the strengthening model of the plugging zone, “rigid bridging+elastoplastic filling+lacing wire of fiber+film‐forming seal,” is a better model, and experiments prove that it can form a tight pressure‐bearing plugging zone, preventing drill‐in fluid loss. The research results provide a theoretical and technical basis for the lost circulation control of fractured gas formations.