Permeability is one of the most fundamental reservoir-rock properties required for modeling hydrocarbon production. However, the ultrafine pore structure of shale-gas reservoirs (pore-throat radii in the range of 1 -200 nm) cause the violation of the basic assumptions behind Darcy’s law. Depending on a combination of pressure-temperature conditions, pore structure and gas properties, non-Darcy flow mechanisms such as Knudsen diffusion, and/or gas-slippage effects will affect the matrix apparent permeability. Additionally, formation compaction and the release of the adsorption gas layer will affect the matrix apparent permeability during reservoir depletion.
The authors of this paper propose a unified matrix apparent-permeability model for shale-gas formations, which unifies non-Darcy flow / gas-slippage mechanisms, adsorption gas layer release, and geomechanical effects into a coherent global model, as shown below.
Mechanisms that alter shale-matrix apparent permeability during production
The fully coupled unconventional reservoir simulator developed in this study provides a comprehensive tool to investigate the combined real-gas nanoflow mechanisms and rock deformation effects on the matrix apparent-permeability, as well as the long-term productivity of hydraulically fractured shale-gas formations.
Conclusions from this research work are:
- Matrix apparent permeability in a shale formation is not only determined by the non-Darcy flow / gas-slippage behavior but also by the intrinsic permeability within the nanopore structure.
- Shale-matrix permeability derived from core samples at laboratory conditions needs to be correlated to reservoir conditions cautiously due to the extreme sensitivity of factors to the pore radius.
- While geomechanical effects (formation compaction) can temporarily dominate the matrix apparent-permeability evolution during the early-production stages, these will be offset by non-Darcy flow / gas-slippage behavior and gas-desorption effects and matrix apparent-permeability will start to increase due to pressure depletion.
- Impaired productivity in fractured shale formations during depletion is most-likely caused by reduction in fracture conductivity, rather than reduction in matrix permeability.
- The gradual release of the molecular adsorption layer has a significant impact on the matrix apparent-permeability evolution for small pore radii.
- Matrix apparent-permeability evolution during production can make a difference in well performance and long-term shale-gas production – even with the presence of a conductive natural-fracture network.
This summary, written by Special Projects Manager Nancy Musick, contains highlights of the following paper: Wang, H. Y. and Marongiu-Porocu, M. 2015. Impact of Shale-Gas Apparent Permeability on Production: Combined Effects of Non-Darcy Flow / Gas Slippage, Desorption, and Geomechanics. SPE Res Eval & Eng. SPE-173196-PA (in press; posted 7 October 2015).
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Presenter: Carlos Avila, Senior Facilities Engineer for Advanced Production Systems, Chevron
When: Thursday, 19 November from 1100 to 1300 hours Central Time
Where: Norris Conference Center, CityCentre, 816 Town and Country Blvd., Suite 210, Houston, Texas
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1100-1130 Registration and Networking
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1200-1300 Presentation and Q&A
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On 27 October at 1200, Ruth Perry and Stephen Truchon will give a live presentation on Building Public-Private Partnerships for Regional Long-Term Research and Monitoring.
Shell is working with academic, non-profit, business partners, and government stakeholders to develop and implement long term environmental monitoring programs. These programs, or public-private partnerships (PPPs), help Shell to operate safely and responsibly in the marine offshore environment.
Register for Howard Duhon’s web event on 22 October at 1200 to listen to a live presentation on how to be an effective Flow Assurance Engineer.
Join Shahab Mohaghegh on 6 October to hear his live web event on the topic of Smart Proxy Modeling for Numerical Reservoir Simulations-Big Data Analytics in E&P.
The SPE Research and Development Technical Section will host a special topical luncheon at ATCE 2015 on Tuesday, 29 September, to facilitate focused dialogue on new materials, techniques, and their applications to oil and gas. In a series of informative and thought-provoking presentations, a panel of industry experts will discuss current uses and future opportunities for these technologies as well as outline the various R&D challenges and needs that must be addressed to overcome their present limitations. A panel question-and-answer session will follow the presentations. Learn more about ATCE and register here.
The Projects, Facilities, and Construction Study Group is pleased to announce their 2015 fall lecture series. The series will highlight and define the role of the facilities engineer and their critical contribution to successful project execution.
Session I: The Value of Facility Engineers
James R. Deaver, 6 October, 1630 (CDT, GMT -6)
Session II: Setting Up Controls and Safety Systems from an Overall View
Lew Skaug, 13 October, 1630 (CDT, GMT -6)
Session III: Design with a View of Operations and Maintainability
Bill Capdevielle, 20 October, 1630 (CDT, GMT -6)
Session IV: The Facilities Engineer of Tomorrow: Faster, Stronger, Smarter—and More Successful Too!
Richard Westney, 27 October, 1630 (CDT, GMT -6)