Analysis of refracturing in horizontal wells: Insights from the poroelastic displacement discontinuity method

Abstract

Summary In this paper, a fully coupled 2‐dimensional poroelastic displacement discontinuity method is used to investigate the refracturing process in horizontal wells. One of the objectives of refracturing is to access new reserves by adding new hydraulic fractures in zones that were bypassed in the initial fracturing attempt. Pore pressure depletion in the vicinity of old fractures directly affects the state of stress and eventually the propagation of newly created hydraulic fractures. Thus, a poroelastic analysis is required to identify guidelines for the refracturing process, in particular to understand the extension of the pore pressure depletion, and eventually, the orientation of new as well as old fractures. We propose a fully coupled approach to model the whole process of child fracture propagation in a depleted area between 2 parent fractures in the same wellbore. This approach omits the need of using multistep workflow that is regularly used to model the process. The maximum tensile stress criterion (σ criterion) is used for hydraulic fracture propagation. The proposed method is verified using available analytical solutions for total stress and pore pressure loading modes on a line fracture in drained and undrained conditions. Then, test cases of multifractured horizontal wells are studied to calculate the time evolution of the stress and pore pressure fields around old fractures and to understand the effect of these fields on the propagation path of newly created fractures. Finally, the effect of the pore pressure depletion on the propagation path of the newly created fractures in the bypassed area of the same wellbore is studied. The results show that the depleted areas around old fractures are highly affected by the extent and severity of the stress redistribution and pore pressure depletion. It is observed that a successful creation of new fractures may only happen in certain time frames. The results of this study provide new insights on the behavior of newly created fractures in depleted zones. They also clarify the relationship between stress change and pore pressure depletion in horizontal wells.

Application of the Fast Multipole Fully Coupled Poroelastic Displacement Discontinuity Method to Hydraulic Fracturing Problems

“…Hence, to improve the computational efficiency, a fast multipole method is implemented in the PDDM algorithm. Rezaei et al (2017) applied the bbFMM to the double summation on the right hand-side of Equations ( 2.3) -(2.5). In this study, bbFMM is applied on both double summation and GMRES iterative solver.…”

“…For a comprehensive review on advances of BEM one may refer to Liu et al (2011). A special formulation of the boundary element method, known as displacement discontinuity method (Crouch, 1976), is extensively used to study hydraulic fracturing problems (Curran and Carvalho, 1987;Carvalho, 1991;Detournay et al, 1989;Ghassemi et al, 2013;Peirce and Bunger, 2014;Safari and Ghassemi, 2014;Wu and Olson, 2015;Rezaei et al, 2018). The host medium of hydraulic fractures is poroelastic and contains discontinuities.…”

Three-Dimensional Geomechanical Modeling and Analysis of Refracturing and “Frac-Hits” in Unconventional Reservoirs

“…In this study, the Newton-Raphson method is used to calculate the fracture propagation angle. Using the maximum principal stress (σ 1 ) as defined in Equation (18) with the assumption of stress component σ z = 0, Schöllmann et al [49] defined an equivalent stress intensity factor as:…”

Numerical Simulation on Deflecting Hydraulic Fracture with Refracturing Using Extended Finite Element Method

“…Depending on the purpose, refracturing treatment can be applied to realize the far-field or near-wellbore diversion of the fractures. So far, several scholars have investigated the influence of the plugging and diverting technology on the deflecting geometries of refracturing fractures [6,7]. Laboratory fracturing experiments have been widely used to investigate the propagation behavior of refracturing hydraulic fractures [8][9][10][11].…”