Exploration and Production Technologies
New Generation Hydraulic Fracturing Model for Horizontal Wells Last Reviewed 6/19/2014

DE-FE0010808

Goal
The goal of this project 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 estimated ultimate recovery determinations, and reduce overall horizontal well costs.

Performers
University of Texas at Austin, Austin, TX, 78712
University of Texas–San Antonio, San Antonio, TX, 78249

Background
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 an 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 exist that model the propagation and performance of simultaneous multiple fractures in horizontal wells.

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.

Impact
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.

Accomplishments (most recent listed first)

  • Developed an efficient algorithm and C++ code for the parallel coupling of peridynamics formulation of porous flow and fluid pressure-driven poroelastic response of the reservoir
  • Developed the coupling strategy for the recently developed peridynamics porous-flow formulation and existing peridynamics solid mechaics formation. The coupled peridynamics model has been validated for a purely elastic deformation with a two-dimensional consolidation problem and for two-dimensional bi-wind planar fracture propagation. Results were presented at the Hydraulic Fracturing and Sand Control JIP meeting on April 22, 2014.
  • The project team developed a novel, generalized, non-local, state-based peridynamic formulation for anisotropic transient fluid flow in an arbitrarily heterogeneous and fractured porous medium.
  • Dr. John Foster organized a workshop in San Antonio entitled “Workshop on Non-local Damage and Failure: Peridynamics and other Non-local Models".
  • Dr. Kariyar presented a paper entitled “A Peridynamic Formulation of Coupled Mechanics Fluid Flow Problem".

Current Status (June 2014)
The project team is finalizing their Continuation Application to request transition to the next phase of the project.

Project Start: October 1 2012
Project End: September 30, 2015

DOE Contribution: $1,038,087
Performer Contribution: $554,367

Contact Information:
NETL – William Fincham (william.fincham@netl.doe.gov or 304-285-4268)
University of Texas at Austin – Mukul M. Sharma (msharma@mail.utexas.edu or 512-471-3257)

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