Research on casing deformation mechanism and prevention measures based on micro-seismic signal distribution

Abstract

Casing deformation is a severe problem in shale gas well development. The field data show that multiple deformations usually occur in the same casing well, and the distance is close, and the degree of deformation is different. In this paper, firstly, based on the distribution of micro-seismic event points in the Ning M well, the fracture group is inverted, and to establish the finite element numerical model to simulate the multi-stage fracturing, Then, the stress at each point of the casing is analyzed with the fracturing time, the circumferential stress at each point after fracturing and the axial stress of casing, and the displacement variation of casing in the directions of maximum, minimum and vertical principal stress are discussed. Finally, the effect of the intensive fracturing technology on controlling casing deformation is discussed. The results show that: a) Casing stress increases in different amplitude at a local point, circumferential direction, an axial direction, and regional stress difference is formed; b) Some local areas around the wellbore are subjected to twice or more re-fractures, and the corresponding rock properties (such as elastic modulus and Poisson's ratio) will change differently; c) Casing deformations with different directions and displacements appear in some reconstructed areas, showing “S” shape deformation, consistent with the actual deformation situation on site; d) The intensive fracturing technology can alleviate the non-uniformity of fracturing and reduce the non-uniform load of the casing, and effectively reduce the casing deformation rate after field application.