Laboratory Investigation Fracture Penetration in Multi-Interlayers with the Cyclic Hydraulic Fracturing

Abstract

In the tight reservoirs of Ordos Basin, shale interlayers are abundant. The mechanical properties of interlayers are different greatly from the adjacent sandstones, affecting the vertical propagation of hydraulic fractures, and resulting in a poor reservoir simulation with conventional hydraulic fracturing. The cyclic fracturing is an effective method to improve the efficiency of stimulation in such reservoirs. To verify the penetrating feasibility of hydraulic fractures with the cyclic fracturing and the conventional hydraulic fracturing, stimulation tests with true triaxial stresses are used to simulate the cyclic hydraulic fracturing in outcrop blocks of 300 × 300 × 600 mm. Hydraulic fractures form in the shale interlayer and penetrates both neighboring layers of sandstones. From visual observations and 3D scanning of the fractures, hydraulic fracture penetrations shows that: (1) Hydraulic fractures in the shale interlayer are complex, and a series of horizontal fractures along the bedding exist, which makes it difficult for fractures penetrate into the adjacent sandstones with conventional hydraulic fracturing; (2) Different from conventional hydraulic fracturing, hydraulic fractures can penetrate the neighboring sandstones from shale interlayer with the cyclic fracturing.