Simulating production from shale reservoirs with upscaled hydraulic fractures

Abstract:

A key challenge in simulating oil/gas production from fractured unconventional shale reservoirs is the limited knowledge on fracture characteristics. This problem is further complicated by the observed multi-stranded fracture propagation from single perforation cluster. Resolving such swarms of parallel, closely-spaced hydraulic fractures increases the required computational cost and adds additional uncertainties to the simulation results.

Recent advances in simulating fracture propagation have enabled generating complex fracture shape and aperture field, as well as upscaling fracture swarms into a single equivalent hydraulic fracture for each perforation cluster. It reduces computational cost, but poses challenges when simulating the upscaled flow field because of (i) nonlinearity between flow and aperture, and (ii) underestimation of the stimulated reservoir volume (SRV) after upscaling.

The present study focuses on simulating multiphase production from unconventional reservoirs based on the upscaled hydraulic fractures. A sensitivity study to the fracture characteristics is performed to understand the effects of complex fracture geometry on production rate. A modified permeability is estimated to handle the nonlinear effects during upscaling. The enhanced SRV for the swarm is modeled with a dual-permeability approach.

Simulation results highlight the influence of fracture shape and aperture on production. Improved agreements between the upscaled and the fully resolved simulations are observed when modifications on both fracture permeability and SRV permeability are performed. Otherwise the upscaled model tends to deviate from the fully resolved model, especially at early stages when flow is strongly affected by fracture permeability and the SRV.