Title: Coupled flow, stress and damage modelling of interactions between hydraulic fractures and natural fractures in shale gas reservoirs

Authors: Hai-Yan Zhu; Xiao-Chun Jin; Jian-Chun Guo; Feng-Chen An; Yong-Hui Wang; Xiang-dong Lai

Addresses: State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, School of Petroleum and Natural Gas Engineering, Southwest Petroleum University, 610500 Chengdu, China ' Energy and Geoscience Institute, University of Utah, 423 Wakara Way, Suite 300, Salt Lake City, Utah 84108, USA ' State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, School of Petroleum and Natural Gas Engineering, Southwest Petroleum University, 610500 Chengdu, China ' State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, 102249 Beijing, China ' Research Institute of Petroleum Exploration and Development-Langfang, Petrochina, 065007 Langfang, China ' Drilling and Production Technology Research Institute of Chuanqing Drilling Engineering Co., Ltd., Petrochina, 618300 Guanghan, Sichuan, China

Abstract: Hydraulic fracturing in naturally fractured shale gas reservoirs is a typical coupled damage and seepage problem. Damage inside natural fractures, caused by either shear stress or tensile stress, can greatly increase the fracture permeability. Additional stress caused by fluid seepage bridges the connectivity among adjacent natural fractures, achieving the stimulated reservoir volume (SRV). The work couples the damage and fluid flow into the Mohr-Coulomb failure criterion for the description of the natural fractures reactivation. Hydraulic fracture is first discretised by the visco-elastic damage pore pressure cohesive elements (PPCE); then by combining the dynamic evolutions of damage, porosity and permeability, a flow, stress and damage (FSD) model of hydraulic fracture and natural fracture system is proposed. The hydraulic stimulation is successful if the permeability of the shale gas reservoir can be improved from the order of nano-Darcy to milli-Darcy. The case study on stimulated reservoir area (SRA) for Q-1 shale gas well in Sichuan Basin agrees with the field data and published data in literatures. [Received: April 6, 2015; Accepted: August 9, 2015]

Keywords: hydraulic fracturing; fracking; numerical simulation; natural fractures; shale brittleness; coupled flow; shear stress; tensile stress; fracture permeability; damage modelling; fluid seepage; shale gas reservoirs; hydraulic fractures; fluid flow; porosity; hydraulic stimulation; China; modelling.

DOI: 10.1504/IJOGCT.2016.080095

International Journal of Oil, Gas and Coal Technology, 2016 Vol.13 No.4, pp.359 - 390

Received: 11 Apr 2015
Accepted: 09 Aug 2015
Published online: 02 Nov 2016 *