Hydraulic fracture stimulation is generally designed and analyzed on the assumption that stimulation produces a single planar tension fracture. Microseismic monitoring and breakthroughs to offset wells have long provided evidence of the existence of reactivated natural fractures and induced fracture networks. Coring of offset wells in the HFTS-1 In Situ Experiment has demonstrated that reactivated natural fractures and induced fracture networks can contain proppant at significant distances from the stimulated perforations. The goal of this paper is to utilize field evidence from HFTS-1 to improve modeling and analysis of reactivated natural fractures and induced fracture networks, providing an alternative to oversimplified single fracture approaches such as PKN and KGD.
The HFTS-1 project provides an extensive dataset of natural fracture, geomechanical, geophysical, and hydraulic fracture data. Intervals in the Upper Wolfcamp and Middle Wolfcamp were stimulated. Response to stimulation was monitored using microseismic methods, and proppant was recovered through coring carried out post-stimulation. This paper presents a discrete fracture network geomechanical model developed using the HFTS-1 dataset. This model simulates the pressure pulse and proppant distribution through induced hydraulic fractures and natural fracture networks. The model is designed to help understand the significant differences in the spatial pattern of microseismic responses, and the pattern of proppant found in induced hydraulic fractures and reactivated natural fractures in a slant well drilled after stimulation.
The model is also intended to address essential issues of hydraulic fracture stimulation:
• Where do injected fluids and proppants go? Are they exclusively in induced tension fractures, or is there a significant role for pre-existing natural fractures, including those that are reactivated and inflated during stimulation ?
• What is the geomechanical and hydraulic significance of induced microseismicity? How do these events reflect induced tension fractures and reactivation of pre-existing natural fractures ?
The first Hydraulic Fracture Test Site (HFTS-1) is a field research experiment conducted in the Midland Basin of west Texas (Fig. 1) supported by industry, government and academic partners (Ciezobka et al., 2018). The primary goals of HFTS-1 were to collect high-quality data sets from the drilling and completion of an unconventional reservoir, and to address fundamental questions of the hydraulic fracturing process.