Mechanisms and Influence of Casing Shear Deformation near the Casing Shoe, Based on MFC Surveys during Multistage Fracturing in Shale Gas Wells in Canada

Abstract

Casing shear deformation has become a serious problem in the development of shale gas fields, which is believed to be related to fault slipping caused by multistage fracturing, and the evaluation of the reduction of a casing’s inner diameter is key. Although many fault slipping models have been published, most of them have not taken the fluid-solid-heat coupling effect into account, and none of the models could be used to calculate the reduction of a casing’s inner diameter. In this paper, a new 3D finite element model was developed to simulate the progress of fault slipping, taking the fluid-solid-heat coupling effect during fracturing into account. For the purpose of increasing calculation accuracy, the elastoplastic constitutive relations of materials were considered, and the solid-shell elements technique was used. The reduction of the casing’s inner diameter along the axis was calculated and the calculation results were compared with the measurement results of multi-finger caliper (MFC) surveys. A sensitivity analysis was conducted, and the influences of slip distance, casing internal pressure, thickness of production and intermediate casing, and the mechanical parameters of cement sheath on the reduction of a casing’s inner diameter in the deformed segment were analyzed. The numerical analysis results showed that decreasing the slip distance, maintaining high pressure, decreasing the Poisson ratio of cement sheath, and increasing casing thickness were beneficial to protect the integrity of the casing. The numerical simulation results were verified by comparison to the shape of MFC measurement results, and had an accuracy up to 90.17%. Results from this study are expected to provide a better understanding of casing shear deformation, and a prediction method of a casing’s inner diameter after fault slipping in multistage fracturing wells.

Development of a Homogenous Cement Slurry Using Synthetic Modified Phyllosilicate while Cementing HPHT Wells

“…Xi et al [13] studied the effects of the mechanical parameters of the cement sheath on the decrease of the internal diameter of the casing. They concluded that as the cement sheath elasticity modulus increases, the decrease of the internal diameter of the casing will reduce.…”

FEM Simulation of Fault Reactivation Induced with Hydraulic Fracturing in the Shangluo Region of Sichuan Province

“…Slow and steady slip occurring on major faults in the vicinity of some shale gas wells during fracturing process is observed [8,9]. Observations show that fault slip leads to casing deformation and the changes in shear stress during fault activity are associated with seismic events [10][11][12]. Currently, the Shangluo region in Sichuan has become a mature shale gas development area, where five earthquakes with magnitudes greater than 4.0 (M W > 4.0) occurred during hydraulic fracturing operations [13,14].…”

An application of FEA and machine learning for the prediction and optimisation of casing buckling and deformation responses in shale gas wells in an in-situ operation

“…The literature has documented some of the major reasons attributed to the casing buckling and deformation phenomena based on field experience from notable shale gas provinces. For example, in China - Xi et al (2019) pointed out that fault slippage in multistage fracturing caused casing shear failure. Also, according to and Wang et al (2018) fracturing activates pre-existing fractures that lead to casing shear buckling.…”