Study of the effects of hydraulic fractures on gas and water flow in shale gas reservoirs

ABSTRACT

Horizontal drilling and multi-stage hydraulic fracturing are the two key technologies for the successful development of shale gas reservoirs. However, there exist large uncertainties in optimizing hydraulic fracturing which affects water retention into shale matrix and gas productivity. In this work, a basic reservoir model with six-stage hydraulic-fracturing treatment was constructed to understand water retention and gas production in shale gas reservoirs. Gas diffusion, gas desorption, Darcy flow as well as non-Darcy flow were considered in this model. Then, a sensitivity study was performed to investigate the effects of hydraulic fractures on water retention and gas conductivity. The results indicate that only 34% of the fracturing water could be recovered back to the surface, and most of them remain in shale formations to interfere with gas production. The increase of fracture half-length, fracture width, fracture permeability, and fracture conductivity will reduce water retention while water retention in shale matrix will increase with the increasing of fracture spacing and fracture number. This work can provide a better understanding of the effects of hydraulic fractures on gas and water flow so as to optimize the hydraulic-fracturing treatment in shale gas reservoirs.

KEYWORDS:

• Shale gas reservoir
• hydraulic fracture
• sensitivity analysis
• gas desorption
• water retention
• gas production

Acknowledgments

This work was supported by the National Natural Science Foundation of China (No. 11802312 and No. U1762216) and by Open Fund (PLN201810) of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University). We also thank the support from the Youth Foundation of Key Laboratory for Mechanics in Fluid Solid Coupling Systems, Chinese Academy of Sciences.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

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Additional information

Funding

This work was supported by the National Natural Science Foundation of China [No. 11802312 and No. U1762216]; Open Fund of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (Southwest Petroleum University) [PLN201810].

Notes on contributors

Yujin Wan

Yujin Wan is a senior engineer of full professor at PetroChina Research Institute of Petroleum Exploration & Development, Beijing, China. His research focused on reservoir characterization, gas reservoir engineering and numerical simulation in reservoirs.

Zhiye Chen

Zhiye Chen is a senior student at Petroleum Engineering School, Southwest Petroleum University, Chengdu, China, and her major is petroleum engineering.

Weijun Shen

Weijun Shen is an associate professor at Institute of Mechanics, Chinese Academy of Sciences (CAS), Beijing, China. He has over 9 years research experience on reservoir characterization, fluid flow and transport, numerical calculation and simulation in reservoirs, and published over 40 journal papers, book chapters and peer-reviewed conference papers on the related fields.

Zexi Kuang

Zexi Kuang is a senior student at School of Civil and Transportation Engineering, Beijing University of Civil Engineering and Architecture, Beijing, China, and his major is civil engineering.

Xiaohua Liu

Xiaohua Liu is a senior engineer at PetroChina Research Institute of Petroleum Exploration & Development, Beijing, China. Her research focused on gas reservoir engineering and numerical simulation in reservoirs.

Wei Guo

Wei Guois a senior engineer at PetroChina Research Institute of Petroleum Exploration & Development, Beijing, China. Her research focused on gas reservoir engineering and numerical simulation in reservoirs.

Yong Hu

Yong Hu is a senior engineer at PetroChina Research Institute of Petroleum Exploration & Development, Beijing, China. His research focused on fluid flow in gas reservoirs and physical simulation in reservoirs.