Numerical Modeling of Well Interference Across Formations at the Hydraulic Fracturing Test Site

Recent field experiments from the Hydraulic Fracturing Test Site (HFTS) show that both horizontal inter-well communications within the same formation and vertical inter-well communications across formations are observed through extensive proppant, fracturing fluid and hydrocarbon tracer tests. The HFTS contains a thin limestone layer that lies between the Upper and Middle Wolfcamp formations, which had been regarded as a weak barrier to contain a fracture's height growth. To understand the mechanisms for observed vertical communications, we use a high-resolution, fully-coupled finite element/finite volume code to model the 3D growth of hydraulically driven fractures under the combined influence of formation barriers and reservoir depletion. A 3D geomechanical model is built to quantitatively evaluate various geological settings to identify the primary factors that affect the breakthrough across a barrier between formations due to the reservoir depletion. This numerical modeling, along with collected microseismic events, tracer, and pressure interference tests, provides an improved understanding of the fracture development in the HFTS.