A study on casing deformation failure during multi-stage hydraulic fracturing for the stimulated reservoir volume of horizontal shale wells

Abstract

Volume fracturing technique has effectively helped develop unconventional oil and gas reservoirs in recent years. At the same time, new problems of casing deformation failure occurred. Based on the drilling and well completion data, microseismic surveillance data, theories of fracture mechanics, rock damage mechanics and rock failure criterion, this paper established a finite element model of the formation of effective stimulated reservoir volume, including clustering perforation casing for X-1 h shale gas horizontal well, to address the problems. The research results indicate: 1) the stress deficit of zero stress areas and tension stress areas occurred within the range of stimulated reservoir volume during the process of volume fracturing. And, the state of this stress deficit, which would make clustering perforation casings of horizontal wells “hanging” in the formation to some extent, resulted in certain degree of deflection deformation radically and S-shape deformation axially. 2) the problem of casing deformation failure remains fundamentally unsolvable through simply improving casing grade and wall thickness to increase flexural strength. 3) the key to solve casing deformation failure is the reasonable spacing design of multi-stage fracturing. The methods and achievements in the paper provide theoretical supports for the popularization and application of shale stimulated reservoir volume and controlling the S-shape deformation failures of the horizontal multi-cluster perforation casing.