Joseph Morris (15-ERD-010)
Developments in horizontal drilling and hydraulic fracturing have resulted in a dramatic increase in gas and oil production in the United States. Increases in hydrocarbon extraction from unconventional resources have primarily come from shale gas and oil resources, where hydraulic fracturing is used to increase formation permeability and enable production. Despite technological successes, the vast majority of shale formations remain untapped because of an inability to effectively produce fracture networks in these types of shale. In these cases, as much as 90% of the resource is left in the ground, some formations cannot be produced, and water availability precludes hydraulic fracturing in water-stressed regions. Dynamic stimulation of reservoirs using energetic materials provides a possible alternative to hydraulic fracturing. Enhancement of fracture network connectivity via dynamic stimulation must consider the rate at which energy is released and the peak pressures generated, in addition to the geometry and temporal sequencing of explosive detonations. We plan to develop the necessary computational tools to allow the design of dynamic stimulation. We will perform simulations to determine the efficacy of dynamic stimulation as a function of rock type, in situ stress, pre-existing fracture network, energetic materials, and detonation geometry.
We expect to develop a modeling capability for the design of dynamic stimulation procedures to enhance hydrocarbon resource recovery and to extend such methods to previously unproductive reservoirs. We will couple continuum and discrete representations of fracture to develop a computational workflow capable of describing high-strain rate, near-field deformation and lower-strain rate, far-field fracture evolution. This may require treating the different temporal and spatial regimes with different simulations. If successful, these tools can be used by industry to enhance the permeability and resource recovery from formations that cannot be produced via hydraulic fracturing. We will also explore developing design methodologies to enhance recovery above those attainable via fracturing and extend oil and gas production from unconventional resources to areas where sufficient water for hydraulic fracturing is not available. In addition, national security concerns such as the detection of clandestine nuclear tests, design of earth-penetrating warheads, and defeat of hardened, deeply buried targets will benefit from this project because they require the simulation of soil and rock mechanics behavior.
Our simulation capability will allow design of new resource stimulation procedures to enhance hydrocarbon resource recovery and to extend the range of such methods to previously unproductive reservoirs. The capability will enhance our energy security and environmentally responsible exploitation of domestic hydrocarbon resources, in support of the Laboratory's strategic focus area in energy and climate security. The computational methodology will also be applicable to efficient recovery of heat in enhanced geothermal systems, and benefits LLNL's high-performance computing, simulation, and data science capability.
FY16 Accomplishments and Results
In FY16 we (1) commenced the extension of the XFEM (extended finite-element code) capability in GEOS (hydraulic fracturing simulation code) from a two- to a three-dimensional capability (see figure); (2) benchmarked this approach against alternatives; (3) continued developing three-dimensional continuous interface reconstruction in GEODYN (geological drilling simulation code) to enable higher-fidelity modeling of dynamic fracturing; (4) transferred the Lagrangian code GEODYN-L sub-grid-scale treatment for shock propagation within cracks into GEOS to support explosive-driven-fracture within the GEOS framework; (5) validated the approach by benchmarking GEODYN, GEODYN-L, ALE3D (three-dimensional arbitrary Lagrange–Eulerian code), and GEOS; and (6) performed studies of the role of high-pressure compressible fluid flow in enhancing extension of explosive-driven fractures using these new capabilities.
Publications and Presentations
- Annavarapu, C., et al., A phantom node approach for modeling complex fracture networks. (2016). LLNL-PRES-675720.
- Annavarapu, C., et al., “A local crack-tracking strategy to model three-dimensional fractures with embedded methods.” Comp. Meth. Appl. Mech. Eng. 311, 815 (2016). LLNL-JRNL-696164. http://dx.doi.org/10.1016/j.cma.2016.09.018
- Morris, J. P., et al., Parametric study of energetic simulation for geothermal applications. 50th U.S. Rock Mechanics/Geomechanics Symp., Houston, Texas, June 26–29, 2016. LLNL-CONF-684717.
- Morris, J. P., et al., Parametric study of energetic simulation for geothermal applications. (2016). LLNL-PRES-695009.