Experimental Investigation about Influence of Natural Fracture on Hydraulic Fracture Propagation under Different Fracturing Parameters

The complex interaction between hydraulic and natural fracture was believed to have a significant impact on hydraulic fracture complexity. Extensive theoretical and experimental works had proved this interaction was affected by several parameters, such as stress difference, approaching angle, frictional coefficient and fracturing parameters etc. However, only engineering parameters, such as pump displacement and viscosity of fracturing fluid, could be controlled by field engineers. How these two parameters affect the interaction remain poorly understood. In this study, a piece of white paper with the dimensions of 200 mm×150 mm×0.1 mm was spread to simulate a planar natural-fracture in the specimen. Two groups of fracturing tests were conducted under tri-axial stresses in large-sized fracturing system. In the first group, different pump displacements with the same viscosity of fracturing fluid were applied. In the second group, fracturing fluid with different viscosities was applied while pump displacement were strictly the same. Experimental results showed that hydraulic fracture can cross the natural fracture under large pump displacement and high viscosity. A critical pump displacement and a critical viscosity were observed respectively. Above this critical displacement or above this critical viscosity, hydraulic fracture can cross the natural fracture; below this critical displacement or below this critical viscosity, hydraulic fracture only propagates along the plane of the nature fracture to its ends rather than cross it. These two critical values can help field engineer design the fracturing parameters.