Fully Coupled Finite Element Model to Study Fault Reactivation during Multiple Hydraulic Fracturing in Heterogeneous Tight Formations

Abstract

Multiple hydraulic fracturing is a proven stimulation technique to improve hydrocarbon production especially in tight, unconventional hydrocarbon bearing reservoirs. A two dimensional (2D) plane strain model, based on linear elastic fracture mechanics (LEFM), has been developed to study multiple fracture propagation and their impact on reactivation of underground discontinuities such as faults. New model solves coupled non-local relationship between fracture width and net pressure in the fracture and non-linear dependence of fluid flow on fracture width and its linear dependence on pressure gradient using finite element method.In this paper, multiple hydraulic fracturing with different number of fractures, fracture spacing and reservoir rock properties are considered. It is found that the number of hydraulic fractures and their spacing significantly impacts fractures geometry and ultimately production performance. The impact found to be more pronounced in heterogeneous reservoir with multiple layers. Slip-tendency analysis performed to investigate the possibility of fault reactivation and discontinuities failure in surrounding areas. Simulation results clearly show dynamics of stable and unstable zones around the hydraulic fracturing area. Discontinuities failure in reactivation zones leads to increase the permeability of formation therefore improving hydraulic fracturing performance. This study is a unique approach for our further understanding of multiple hydraulic fracturing, and it is important for the development of sound numerical hydraulic fracturing optimization models.

Mixed finite element formulation for dynamics of porous media

“…strain energy, and dissipated energy. We note that the increment of the work done by constraint pressure is zero, E C = 0, since the terms inside the parentheses in (20) 6 are the discretized constraint equations. Moreover, since the constraint is satisfied at initial time, E C = 0 as well.…”

“…For this also, coupled modeling of geomechanics and fluid flow is required . Moreover, such coupled interaction between mechanical deformation and fluid flow plays an important role in the instability of faults during processes such as hydraulic fracturing and geological carbon sequestration, which could potentially lead to induced seismicity and associated fluid migration . Similarly, in biomechanics, mechanical response of hydrated soft tissues such as brain, skin, and articular cartilage, bones, and even individual cells involves coupled response of a skeleton and pore fluid.…”