Experimental investigation on propagation geometry of hydraulic fracture in compact limestone reservoirs

Large-scale hydraulic fracturing technology is significant in the development of compact limestone reservoirs with low porosity and low permeability. The diagenesis, mineral composition and mechanical properties of the compact limestone reservoirs are greatly different from those of the compact sandstone ones. Hydraulic fracture geometry is complicated under different stress states and construction conditions. Based on the hydraulic fracturing simulation experiments on compact limestone outcrops carried out by using a true triaxial test system, the effects of multiple factors on fracture propagating laws of horizontal well in compact limestone are studied. The results show that hydraulic fractures likely interact with natural ones when the horizontal stress difference ranges from 2 to 8 MPa. A higher fracturing fluid viscosity reduces the possibility of shearing slip and filtration expansion of the natural fractures, forming a relatively less complex fracture network. Under the strike-slip fault stress state (), the horizontal hydraulic fracture can be easily generated and propagates along the bedding plane, especially when the direction of borehole is parallel to the bedding plane. The fracturing with variable pump rates can reactivate more natural fractures, forming a more complicated fracture network. Acidizing treatment for openhole section can significantly reduce the fracture pressure, and the decrease range of fracture pressure gradually increases with the increase of acidizing treatment time. This study may provide a reference for field fracturing treatment.