Effect of Fracability Index on Fracture Propagation: A Case Study of LF Oilfield in South China Sea

The South China Sea is rich in deep Paleogene oil and gas resources. However, due to the poor formation properties and strong heterogeneity of reservoirs, hydraulic fracturing is needed to realize commercial exploitation. In order to explore the effect of the fracability index on fracture propagation, the rock brittleness and mechanical characteristics of reservoirs in LF Oilfield in the South China Sea were comprehensively studied, and the fracability index calculation model suitable for the LF Oilfield in the South China Sea was established. The fracability indexes of the three sublayers of the Wenchang Formation in the target layer in LF Oilfield in the South China Sea were determined to be 0.75, 0.45, and 0.92 by the model, respectively. Outcrop rock samples with different fracability indexes of LF Oilfield in the South China Sea were selected, and the physical simulation test of hydraulic fracturing was carried out by using the physical simulation test device of true triaxial hydraulic fracturing. The test results show that the artificial fractures in the three sublayers of the Wenchang Formation in the target layer are easy to initiate at the position where bedding and natural fractures develop, but they do not initiate simultaneously at each perforation. As the fracability index is higher, complex fracture morphology will be more likely to form. The research results have important guiding significance for evaluating the fracability of low-porosity and low-permeability offshore oil and gas reservoirs, selecting the location of sweet spots, and optimizing the fracturing scheme.