A numerical simulation study of fracture reorientation with a degradable fiber-diverting agent Daobing Wang a, b, c , Fujian Zhou a, b, * , Wei Ding c , Hongkui Ge a, b , Xinfeng Jia d , Yang Shi c , Xiaoqiong Wang a, b , Xingming Yan e a Unconventional Natural Gas Research Institute, China University of Petroleum, Beijing 102249, China b State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China c Beijing Branch, Research Institute of Petroleum Exploration and Development, China National Petroleum Cooperation, Beijing 100083, China d The Department of Chemical and Petroleum Engineering, University of Calgary, Alberta T2N 1N4, Canada e Langfang Branch, Research Institute of Petroleum Exploration and Development, China National Petroleum Cooperation, Hebei 065007, China article info Article history: Received 8 January 2015 Received in revised form 2 May 2015 Accepted 4 May 2015 Available online Keywords: Fracture reorientation Hydraulic fracturing Mathematical model Fiber Stress field abstract Degradable fiber can temporarily plug a natural fracture or artificial fracture. It has been successfully applied in the stimulated reservoir volume (SRV) fracturing or re-fracturing of unconventional reservoirs. Based on the classical analytical stress field equation, a new mathematical model is established in this paper to model the crack reorientation path after injecting fiber diversion fluid according to the tensile failure criterion. Factors influencing the diverting radius are intensively analyzed through numerical simulation. The results indicate that the horizontal stress difference, fracturing fluid viscosity, and in- jection time (fracturing fluid volume) have larger effects on the diverting radius than do the formation permeability (1e50 mD) and bottomhole pressure (90e160 MPa). The simulation results are successfully verified, matching well with the experimental data from the true tri-axial fracture reorientation tests in the laboratory. The model is successfully applied to the heterogeneous carbonate reservoirs in northwest China. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Hydraulic fracturing techniques are effective means of the economic development of unconventional oil and gas resources. Due to the ultralow matrix permeability, the stimulation reservoir volume (SRV) needs to be expanded by increasing the degree of complexity of the hydraulic fracturing treatment. SRV fracturing can carry out three-dimensional reconstruction of oil and gas layers, form an artificial fracture network to maximize the swept volume of artificial fractures within the reservoir and thereby in- crease the effective permeability to improve oil and gas production. When objective factors of formation, such as large local stress difference, are not conducive to generating a complex fracture network, a temporary blocking agent can be introduced to form an artificial additional shielding and seal cracks and pre-existing flow channels to divert the artificial fractures (Economides and Nolte, 2003; Wang and Zhang, 1998; Wang, 2013). Therefore, diverting fracturing can increase the scope and effectiveness of reservoir stimulation. It is important for stimulating low-permeability res- ervoirs, such as shale gas plays, tight gas reservoirs and deep car- bonate reservoirs. Diverting agent materials is crucial to successful diverting fracturing treatment. Smith et al. (1969) simply viewed the con- ventional diverting agent materials used for fluid diversion. They contain oil or water soluble diverting agents, foam, naphthalene, rock salt, paraformaldehyde and a wax-polymer. Ball-sealer diver- sion is used in casing perforated wells to divert fracturing fluids by temporarily blocking perforations with rubber-coated balls. Nozaki et al. (2013) developed an empirical correlation for ball-sealer performance according to a laboratory experiment. However, these diverting materials have inherent disadvan- tages, such as low seal pressure, incomplete degradation and damage to formation. Zhou et al. (2009) proposed a novel fiber- assisted diversion acid fracturing (acidizing) technique that in- tegrates fracture reorientation and fluid diversion to divert the artificial fractures and enhance the chance of connecting fracture- and-cavern area in deep carbonate reservoirs. The fibers can form * Corresponding author. Unconventional Natural Gas Research Institute, China University of Petroleum, Beijing 102249, China. E-mail addresses: 0546wdb@163.com (D. Wang), zhoufj@cup.edu.cn (F. Zhou). Contents lists available at ScienceDirect Journal of Natural Gas Science and Engineering journal homepage: www.elsevier.com/locate/jngse http://dx.doi.org/10.1016/j.jngse.2015.05.002 1875-5100/© 2015 Elsevier B.V. All rights reserved. Journal of Natural Gas Science and Engineering 25 (2015) 215e225