Advanced science.  Applied technology.


Predicting Induced Permeability from Geomechanical Modeling of Hydraulic Fracturing, 15-R8760

Principal Investigators
Alan Morris
David Ferrill
Ronald McGinnis
Biswajit Dasgupta
Inclusive Dates 
04/01/17 to 03/27/18


Fluid flow through rock is the fundamental process in most energy extraction endeavors, including hydrocarbon exploration and production and enhanced geothermal energy production. In most unconventional oil and gas resource plays, extraction of hydrocarbons from self-sourced reservoirs (e.g., Eagle Ford, Wolfcamp, Marcellus, Bakken, Barnett, Monterey, and Niobrara Formations) is technically challenging because the natural system matrix permeability is very low. A combination of long, horizontal wells (laterals) and aggressive stimulation (hydraulic fracturing to create new fractures and connect to existing fractures) is necessary for economic fluid recovery. For a typical onshore U.S. unconventional well, 60 percent or more of the total well cost goes toward the post-drilling (stimulation) activities. Improvements in the planning and pre-stimulation prediction of hydraulic fracturing are of ever-increasing importance to the economic viability of most unconventional plays.


The objectives of this project were to improve predictive modeling of reservoir stimulation activities by 1) investigating alternative approaches for converting simulated continuum-based inelastic strains into fracture volumes (fracture porosity) and quantitative predictions of induced fracture permeability, and 2) fully integrating natural discontinuity information (e.g., derived from wellbore data or discrete fracture networks) so that contributions of both induced and natural fractures are captured in the analyses. Pre-completion estimates of increased porosity and permeability resulting from reservoir stimulation are highly sought after by the oil and gas industry.

This project built on our established geomechanical approach to hydraulic-fracture modeling, which has employed primarily continuum-mechanics-based, finite-element methods using inelastic (permanent) strains as proxies for the induced fractures. This approach does not explicitly simulate discontinuity formation and, therefore, does not provide a direct measure of permeability enhancement of the system. While these analyses have been successful in simulating complex fracture patterns that our clients consider to be more realistic than standard industry approaches — and, therefore, useful in well planning and design — the lack of induced fracture volume (porosity) and permeability information is hindering the next major advance in modeling induced hydraulic fracturing. A viable option for advancing this work is to incorporate a new user-defined constitutive model into our fundamental continuum-mechanics approach that will explicitly calculate an induced fracture aperture variable. When integrated over the simulation domain, this approach can provide a quantitative measure of the porosity and permeability enhancement. An alternative technique that we are exploring and comparing is an integrated finite element-discrete element modeling approach that explicitly allows new fracture formation and, therefore, computation of new fracture volume.


This project began with a foundation built on our established geomechanical approach to hydraulic-fracture modeling and successfully achieved the goals of 1) investigating alternative approaches for converting continuum-mechanics-based inelastic strains into equivalent fracture volumes and subsequently into quantitative predictions of induced fracture permeability, and 2) integrating natural discontinuity information into the continuum approach so that contributions of both induced and natural fractures are captured in the analyses. By testing the approach on a range of laboratory- and field-scale problems, we have demonstrated the correctness of the theoretical basis, as well as shown that the results are consistent with induced deformation of a natural rock system. The ability to capture the induced fracture volume and corresponding permeability enhancement in a computationally efficient manner represents a significant improvement to our geomechanical modeling capabilities. Further advancements in the simulation of processes like hydraulic fracturing will require a focus on more fully capturing the fluid flow component of this coupled physical process.