Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
Characterizing Stimulation Domains, for Improved Well Completions in Gas Shales
Aetman Engineering of Houston
PCM Technical of Tulsa
Southwestern Energy Company of Houston.
Objectives of the project:
- Develop a method and a prototype screening software tool to characterize how flow properties change within the domain of a well stimulation, both during and after the stimulation.
- Develop two permeability-based diagnostics of the domain stimulation, and relate these to fracture treatment parameters.
- Use the results as a guide to improvements in well stimulations, leading to accelerated gas production and recovery.
- Demonstrate the prototype tool by application to field data. The prototype tool will be designed so that it can be used systematically by an operator to diagnose well stimulations, and point to improvements.
Description of the project, including methods:
The objectives will be achieved by combining the performer’s in-house programs for predicting shear failure (geomechanics basis) and for rate-transient analysis (RTA). The seamless software will require serious development to include post-transient flow, pressure-dependent permeability, and guidelines for proppant design in fracture networks. The screening software will be designed to quantify both injection permeability (by predicting shear failure and matching a microseismic pattern), and production permeability (by using RTA to match gas rate), and to compare them with virgin permeability. The next step is to program into the software tool two different permeability-based diagnostics (production permeability and loss of injection permeability), and to relate these to fracture treatment parameters (such as poor fracture fluid cleanup, damage by chemicals in the frac fluid, and inadequate proppant design), for the purpose of improving well stimulations. The next objective is to mitigate the injection perm loss by creative design of proppant injection to prop open the natural/induced fractures before they close (i.e., to re-invent proppant design applicable to a fracture network). This will be achieved by a simplified, practical theoretical study of the transport of different proppants through a network of fractures. How to get proppant into a network of fractures, with good coverage, is a critical aspect. The results will be summarized in the software tool so that an operator can be guided to choose a proppant design to improve the domain stimulation. The prototype software tool will be demonstrated by application to field data (microseismic, gas rates, and stimulation parameters) in 6 horizontal wells.
The overall deliverable is a user-friendly software tool, which can be used by operators to fully characterize flow properties of stimulation domains, and provide guidance to improve well stimulations. A second deliverable is a summary of the damaging effects of fracture treatments on natural/induced fractures. A third deliverable is a simplified but practical theoretical analysis and report of proppant transport in a fracture network, including access to fractures, penetration into fractures, and resulting fracture conductivity. The final deliverable is a demonstration of the tool using data from 6 wells in the Fayetteville shale, a proven shale play where there are over 1,000 horizontal multi-stage fracture-stimulated wells for comparison.
This is an R&D project, and the potential is attractive. The key is diagnosing and improving well stimulations, with a direct impact on gas production and recovery. The new perm-based diagnoses should be insightful in regard to improving well stimulations. The correlations with fracture treatment parameters should lead to significant improvements. For example, if by changing proppant design to retain more of the injection permeability, gas rates could be boosted by up to a factor of two, which would be an enormous benefit to gas shales (this scenario appears possible). The potential impact, on production and reserves, of the field demonstration will be insightful at the least, and could be revolutionary at best. The learnings should have a high degree of application to other shales.
Other participants involved in the work:
Aetman Engineering of Houston, PCM Technical of Tulsa, Southwestern Energy Company of Houston.
Organizations providing cost-share:
Higgs-Palmer Technologies, PCM Technical, and Southwestern Energy Company
Principal Investigator: Ian Palmer