Numerical Study of Simultaneous Multiple Fracture Propagation in Changning Shale Gas Field

Abstract

Recently, the Changning shale gas field has been one of the most outstanding shale plays in China for unconventional gas exploitation. Based on the more practical experience of hydraulic fracturing, the economic gas production from this field can be optimized and gradually improved. However, further optimization of the fracture design requires a deeper understanding of the effects of engineering parameters on simultaneous multiple fracture propagation. It can increase the effective fracture number and the well performance. In this paper, based on the Changning field data, a complex fracture propagation model was established. A series of case studies were investigated to analyze the effects of engineering parameters on simultaneous multiple fracture propagation. The fracture spacing, perforating number, injection rate, fluid viscosity and number of fractures within one stage were considered. The simulation results show that smaller fracture spacing implies stronger stress shadow effects, which significantly reduces the perforating efficiency. The perforating number is a critical parameter that has a big impact on the cluster efficiency. In addition, one cluster with a smaller perforating number can more easily generate a uniform fracture geometry. A higher injection rate is better for promoting uniform fluid volume distribution, with each cluster growing more evenly. An increasing fluid viscosity increases the variation of fluid distribution between perforation clusters, resulting in the increasing gap between the interior fracture and outer fractures. An increasing number of fractures within the stage increases the stress shadow among fractures, resulting in a larger total fracture length and a smaller average fracture width. This work provides key guidelines for improving the effectiveness of hydraulic fracture treatments.

Stress-dependent unstable dynamic propagation of multiple hydraulic fractures: a review of stress shadow effects and continuum-discontinuum methods

“…Thus, the smaller the cluster spacing is, the stronger the stress shadow effects are, which significantly reduces the perforation efficiency (Escobar et al. , 2019; Xia and Zeng, 2018; Xie et al. , 2019).…”

“…When the cluster spacing is larger, the stress shadow effects decrease and the fracture propagates almost in a straight line. Thus, the smaller the cluster spacing is, the stronger the stress shadow effects are, which significantly reduces the perforation efficiency (Escobar et al, 2019;Xia and Zeng, 2018;Xie et al, 2019). The optimal cluster spacing of simultaneous fracturing for two fractures is 20-30 m, while the optimal cluster spacing of simultaneous fracturing for three fractures is 30-40 m (Tang et al, 2019a).…”

Phase Field Modeling of Multiple Fracture Growth in Natural Fractured Reservoirs

“…As the Q 0 increases, the fluid distribution in each fracture is more uniform. The fluid distribution is controlled by the governing equations Equation (26) and Equation (27). The perforation friction is proportional to the square of the injection rate.…”

“…[26] built a three-dimensional model to consider the effect of stress shadowing and multihorizontal well interwell stress interference on hydraulic fracture propagation in multiple fracture propagation. [27] used a complex fracture propagation model (XFRAC) to study the effect of group construction engineering parameters on the uniform propagation of fractures. [28] found that the stress shadowing effect caused by the interaction between multiple fractures increases the effective closure stress.…”

Investigation on Nonuniform Extension of Hydraulic Fracture in Shale Gas Formation

“…However, there are some different properties of shale formation between two areas which are shown in Table 1, so the extension of multifracture and fracture geometry in the reservoir is likely to exhibit diversely. Additionally, few studies focus on the fracture extension in Changning shale block except Xie et al who mostly discussed hydraulic fractures in only 3 clusters' perforation within one stage [30]. Therefore, based on the geology and engineering characteristics of Changning shale block, investigation of the effects of cluster number, cluster spacing, perforation distribution, and flow rate on fracture propagation in multicluster hydraulic fracturing by the numerical simulation method is indispensable.…”