Advanced Computational Modeling of Proppant Settling in Water Fractures for Shale Gas Production

Abstract

Abstract This paper shows advances in the numerical simulation of proppant transport in hydraulically stimulated fractures for oil and gas production. Water or commonly known "slickwater" hydraulic fracture treatments have become increasingly popular in shale gas. This is widely applied in the Haynesville shale in north Louisiana but, due to the large depths and high pressure, conventional wisdom requires that the intermediate strength proppants (generally 4,000 to 6,000 psi crush strength) should be used. This strength envelope is in the transition between ceramics and sand. Sand, which is lower in cost, also has the advantage of having better transport properties in water fractures. In the paper, a 3-D computational fluid dynamics model with Lagrangian solid particle transport isused to visualize the propagation of sand and other lighter proppants in a simulated fracture. Demonstrated is the proppant settling behavior influenced by proppant density, size and flow rates. The final proppant settling patterns can vary dramatically and may result in significant changes on the fracture’s conductivity. Model assumptions, simplifications and numerical details are discussed along with issues regardingvalidation and simulation strategy. The model geometry is highly idealized (i.e., neglectingfracture tortuosity and expansion during water fracturing, surface roughness and fluid leakoff). The importance of this work lies in the fact that the model can resolve the interactions between fracturing fluid (water) and proppants within complex 3-D geometries, thus providing a better understanding of the fracturing process to allow for possible enhancements to production procedures.