Petroleum (Mar 2022)
Three-dimensional numerical solution and stress cage analysis of high conductive fractures pressure sealing
Abstract
Aiming at the main problems in the design and analysis of well wall strengthening for fractured formations, a three-dimensional (3D) numerical simulation scheme is proposed. The three-dimensional finite element software is used to analyze the mechanical behavior of fractures and the pressure sealing process, and evaluate the stress cage effect. The main features of the model are as follows: (1) The equivalent fractures in the analytical model represent the function sum of the mechanical behavior of all fractures on the well wall, which is a functionally equivalent crack.(2) When evaluating the stress cage effect, the shape of the crack wedge filled with the plugging agent particles is formed by simulating the fractures opening process under the injection pressure, not a given regular shape.(3) In the model of calculating bull heading of block agent, the liquid pressure on the well wall is the injection pressure, which is a variation increased with time. The fluid pressure on the well wall in the stress cage calculation model is generated by the initial pore pressure. (4) The numerical evaluation of the stress cage effect is achieved by calculating the increase amplitude FX of the minimum hoop stress on the well wall. Using this model, several sets of injection pressure design values can be used for pressure plugging numerical simulation and stress cage effect evaluation calculation, and then the optimal and accurate quantitative value of “injection pressure, block agent particle size, safe mud window upper bound” are found through comparison. Finally, through an engineering example of horizontal well drilling pressure sealing in a shale gas reservoir developed by a fracture, we use the above theoretical tools to introduce the process and results of the numerical analysis of the extended mud window drilled in the shale gas fissure reservoir.
