An Anisotropic Permeability Model for Shale Gas Recovery Considering Slippage Effect and Embedded Proppants
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Original Paper
An Anisotropic Permeability Model for Shale Gas Recovery Considering Slippage Effect and Embedded Proppants Jianhua Li,1 Bobo Li,1,2,3,5 Zhihe Wang,4 Chonghong Ren,1 Kang Yang,1 and Shuai Chen1 Received 10 November 2019; accepted 14 March 2020
Hydraulic fracturing has been widely adopted to improve shale gas recovery. A main issue in the implementation of hydraulic fracturing techniques is that proppants made from a variety of materials are normally introduced for the purpose of permeability enhancement. An embedded proppant can significantly alter the original gas flow behavior of shale, which should be taken into account when estimating shale permeability. In this paper, we propose a shale anisotropic permeability model that considers the effect of proppant embedding. Moreover, because the slippage factor is usually not fixed owing to the combined effect of proppant embeddings, any adsorption-induced swelling and stress, a slippage factor formulation is developed to consider the embedded proppant. Finally, an improved shale anisotropic permeability model that considers the combined effect of proppants and slippage is proposed. The validity of the model presented in this paper was assessed by comparing the results with previous experiments, and good agreement was found for the proposed model. The developed model can estimate accurately shale anisotropic permeability, when both the proppant and slippage effect are considered, and can be used to study related problems in the recovery of shale gas resources. KEY WORDS: Shale, Permeability, Slippage effect, Anisotropy, Proppant.
INTRODUCTION In recent years, unconventional oil and gas, mainly shale gas, have gradually changed the energy structure industry (Guo et al. 2016). Because of 1
College of Mining, Guizhou University, Guiyang 550025, PeopleÕs Republic of China. 2 Guizhou Key Laboratory of Comprehensive Utilization of Nonmetallic Mineral Resources, Guiyang 550025, PeopleÕs Republic of China. 3 National & Local Joint Laboratory of Engineering for Effective Utilization of Regional Mineral Resources from Karst Areas, Guizhou University, Guiyang 550025, PeopleÕs Republic of China. 4 School of Civil, Environmental and Mining Engineering, The University of Adelaide, Adelaide 5005, Australia. 5 To whom correspondence should be addressed; e-mail: [email protected]
advances in horizontal drilling and hydraulic fracturing technology, shale gas exploration and development have achieved great success (Ju et al. 2016; Moghadasi et al. 2019). Some countries have also gradually succeeded in commercializing exploiting shale gas (McGlade et al. 2013; Cai et al. 2019). Shale is anisotropic in terms of its mechanical and hydraulic properties under complex geological conditions (Zhang. 2016). During the implementation of hydraulic fracturing technology, shale fractures dynamically to extend and gradually form a complex fracture system. Proppants are often used to sustain available channels for gas flows to sustain a steady recovery of shale gases. Hence, shale perm
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