Investigating the Effect of Geological and Engineering Parameters on the Fracture Height Growth in Naturally-Layered Shale Reservoirs Using 3D Lattice Method

Abstract

Abstract Numerical investigation of the influence of different parameters on hydraulic fracture propagation is fundamental to guide the fracturing parameters optimization of naturally-layered shale reservoir. The shale reservoir contains a large number of bedding planes with lower strength, which have a great effect on the vertical growth of hydraulic fractures. It is believed that the interaction between hydraulic fractures (HF) and bedding planes (BP) has a significant impact on the fracture geometry. In this paper, we used 3D lattice method to establish the hydraulic fracture modelling with multiple horizontal bedding planes, and this model can consider fluid-mechanical coupling effect and the fluid flow in permeable bedding plane. Based on the model, a sensitivity analysis of the key influencing parameters such as vertical stress, cohesion of bedding plane, permeability of bedding plane, injection rate, and fracturing fluid viscosity on the fracture height growth is implemented. The fracture penetration coefficient and the area coefficient of vertical propagation are introduced to evaluate the penetrating ability, and the degree of influence of each factor on the penetrating ability is analyzed and ranked using grey relational analysis (GRA). The simulation results show that the hydraulic fracture tends to penetrate bedding planes under the condition of high vertical stress, high cohesion of bedding plane, low permeability of bedding plane, high injection rate, and high fracturing fluid viscosity. Due to the existence of bedding planes, the morphology of hydraulic fracture is more complex, and the fracture shape presents several forms, typically including "I", "工", and "キ" shape. When the fracture penetration coefficient and the area coefficient of vertical propagation are higher, it is more likely that the hydraulic fracture penetrates the bedding plane directly. Otherwise, it will be arrested and turn to propagate along the bedding planes. Compared with other factors, the vertical stress has the most significant impact on the fracture height growth. The numerical model provides an effective approach for quantitatively analyzing the development of various types of HF/BP interaction behavior. The research results have been applied in hydraulic fracturing of Well X1, and expected stimulation effect is achieved by technical optimization.