How will treatment parameters impact the optimization of hydraulic fracturing process in unconventional reservoirs?

Abstract

Hydraulic fracturing is a very complex process that has not yet been fully understood. Furthermore, the number of stages, length of fracture clusters in each stage, proppant and fracturing fluid compatibilities, optimum spacing length, proppant transport and placement, proppant and frac-fluid compatibility, and optimum spacing are some of the challenges inhibiting successful application of this technique across the world. In this study, we present the impact of fracture-cluster lengths, proppant types and sizes, proppant densities, frac fluid types, fluid viscosities, and injection rates on hydraulic fracturing process. Firstly, we developed a stress profile to determine initiation location and orientation of the hydraulic fractures, and subsequently created the geological layering in the zone of interest. We grouped our investigations into 5 case studies, followed by developing an efficient hydraulic fracturing design approach, and we determined the optimal treatment to achieve maximum recovery. Our results show that fracture clusters with optimal lengths will provide optimized hydraulic fracture treatment. In addition, high-strength proppants is efficient for shale formations with closure stress exceeding 5000 psi to achieve optimum fracture conductivity and fracture half-length. Furthermore, we observed the high-density proppant produced greater fracture lengths and lower dimensionless fracture conductivity (C FD), while the low-density proppant produced greater effective propped-fracture lengths and higher C FD. In some of the cases investigated, we observed that stress shadowing and interference can hinder fracture growth, eventually led to a collapse of some fractures. Our results provide valuable critical decision-making insight for optimizing hydraulic fracturing process in unconventional reservoirs across the world.

Simulation of Gas-Water Two-Phase Flow in Tight Gas Reservoirs Considering the Gas Slip Effect

“…Shale gas reservoirs have extremely low flow capacity, complex fluid fugacity, and interacting gas-water two-phase flow. It has brought many challenges to shale gas production and analytical calculations [2][3][4].…”

“…Gasphase is compressible. (3) The effect of the capillary force of gas and water phases is neglected. (4) The effect of gravity is neglected.…”

Study on the Optimal Volume Fracturing Design for Horizontal Wells in Tight Oil Reservoirs

“…Zhao et al [21] studied the effect of cluster and stage spacing on horizontal well production and proposed an optimization scheme to obtain the maximum capacity. Kolawole et al [22] investigated the impact of construction parameters and fracture parameters on the hydraulic fracturing process and suggested an efficient hydraulic fracturing design method to achieve the maximum recovery. Wang et al [23] applied the finite element numerical simulation method to optimize the half-length and stage of fracture of three types of reservoirs in the Ma 18 block of the Aihu Oilfield.…”