Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
A Geomechanical Analysis of Gas Shale Fracturing and Its Containment
Texas A&M University, College Station, TX
Shale gas reservoirs have heterogeneous geomechanical characteristics that pose challenges to economic gas production. Achieving economic production in nano-Darcy permeability gas-shale reservoirs requires creating a fracture network without penetrating the bounding layers to minimize costs and prevent environmental difficulties. But, hydraulic fracturing results are often poorly predictable, in part because of the resulting complex fracture geometry that arises from intact rock and rock mass textural characteristic and in-situ stress. This has an impact not only on fracture creation but also its containment within the zone of interest to minimize significant environmental consequences. During this project we plan to conduct an integrated experimental and numerical study to accomplish the following objectives: (i) to understand the role of rock texture, fabric, and deformation regime on the nature and extent of induced fractures, (ii) to develop better understanding of the impact of rock property and interfaces/discontinuities characteristics on containing fractures in gas shale reservoirs, and (iii) to numerically study fracture complexity and contained stimulated volume while considering rock heterogeneity and discontinuity based on experimental observations.
The problem is challenging, but the potential to substantially improved gas production from shales with minimum environmental footprint is the main outcome of the project. The information, insights, and modeling capability developed can be used to evaluate real fracture treatments and their potential for migration to unwanted formations. Containment is a factor affecting the acceptance of hydraulic fracturing as a stimulation method in many shale gas areas.
The project is expected to include measurements on reservoir mudstones primarily from the Eagleford, Haynesville, and Marcellus gas shale plays to study 1) texture, fabric and deformation regime characteristics with reference to their impact on the resulting fracture network complexity, 2) style of fracturing (shear vs. tension), and fracture complexity under triaxial loading of core from reservoir and bounding layers (intact and fractured) and representative rock blocks (with discontinuity), 3) numerical simulations based on experiments using models that consider discontinuities and rock strength and elastic heterogeneity based on rock fabric characteristics.
Principal Investigators: Drs. Ahmad Ghassemi, and Steve Holditch, Texas A&M University
Project Duration: 2 years