The project goal is to develop a “new generation” hydraulic fracturing model that will, for the first time, provide an operator with the ability to model the simultaneous propagation of non-planar hydraulic fractures from multiple perforation clusters and create a realistic picture of the stimulated rock volume (SRV) around horizontal wells. The model will be used to simulate the performance of different fracturing fluids and fracture designs to maximize the effectiveness of the SRV to increase well productivity, improve ultimate recovery estimates, and reduce overall horizontal well costs.
University of Texas at Austin, Austin, TX, 78712
University of Texas–San Antonio, San Antonio, TX, 78249
According to a 2011 U.S. Energy Information Administration report, almost all incremental oil and natural gas production in the lower 48 states will come from unconventional resources—shales, low permeability sands, and heavy oil. Production of virtually all the oil and gas from unconventional reservoirs will rely on the application of multiple fractures in horizontal wells. The development of oil- and gas-bearing shale plays largely depends on the cost of drilling and fracturing horizontal wells. Rapid decline rates require that new wells be drilled to maintain existing production rates. A reduction in the cost and environmental footprint of drilling and fracturing will lead to a significant expansion of oil- and gas-bearing shale development. This project aims to develop better methods for substantially reducing these costs while maximizing oil and gas production from the shale reservoirs.
Virtually all current approaches to hydraulic fracture modeling rely on finite difference, finite element, or boundary element methods to solve a fracture formulation. These methods usually use linear-elastic fracture mechanics to determine crack lengths based on the internal pressure driving the fracture open. The discontinuous nature of the cracks causes problems with methods that rely on computing derivatives across domains containing discontinuities and severely limits the applicability of these methods to only the simplest geometries (usually single, planar fractures).
The project’s primary objective is to develop a “new generation” hydraulic fracturing model, based on a peridynamics formulation, that models multiple, non-planar, competing fractures in heterogeneous shales for better well design, improved hydraulic fracturing, enhanced production, reduced drilling and completion costs, and improved shale oil and shale gas production economics. Peridynamics is a recently developed continuum mechanics theory that allows for autonomous fracture propagation. It has been demonstrated and applied to other geo-mechanical and structural problems where material failure was pervasive (e.g., cement structures). Peridynamics allows three-dimensional modeling of arbitrarily complex fracture geometries and the growth of competing and interacting fractures in naturally fractured media. No current models capable of modeling the propagation and performance of simultaneous multiple fractures in horizontal wells exist.
Reducing the high cost associated with drilling and completing long laterals with a large number of hydraulic fractures requires a better understanding of the geometry of these fractures and SRV around the wellbore. Significant questions remain about optimum spacing among horizontal laterals, fracture stages, and perforation clusters. The inability to conduct such an analysis stems from the difficulty in determining, with any degree of certainty, the fracture geometry created through multiple clusters and multiple stages along each lateral and between laterals.
The impact of this work is expected to be widespread and applicable to all oil- and gas-bearing shale resources in North America. Both the proposed modeling and the fracturing recommendations are expected to have an immediate and long-term impact and benefit.
The ability to realistically model hydraulic fracture propagation will provide a starting point for a better understanding of how fracture design affects the stimulated rock volume and well performance. It is anticipated that the new hydraulic fracturing model will lead to recommendations and guidelines regarding cluster spacing, stage spacing, stage sequencing, and fracture design in long horizontal wells for a given set of reservoir conditions. These recommendations should result in significant performance improvements and cost savings, thereby allowing more wells to be drilled and completed for the same annual budget. Increased reservoir drainage due to improved fracturing will result in more economic and longer producing wells, potentially resulting in a 5 to 10 percent increase in the recovery of oil and gas from these unconventional plays and a reduction in well costs of up to 25 percent. The models will be particularly useful for oil-bearing shales that are more likely to have natural fractures and more complex fracture patterns.
The project ended on September 30, 2016. The final report is available below under "Additional Information".
Final Scientific Report [PDF] (December 2016)