Evaluation of deflagration fracturing effect based on the HJC constitutive model

Conventional hydraulic fracturing technology has become a key factor limiting the productivity of offshore oil and gas fields due to its high cost. Therefore, deflagration fracturing technology has emerged as an effective alternative for enhancing production in offshore oil and gas fields, primarily due to its lower costs. The impact load generated by deflagration creates a high-pressure environment, which induces the formation of fractures in the rock. The HJC constitutive model effectively describes the large deformation behavior of rock-like materials under dynamic impact conditions. Therefore, a three-dimensional finite element model of deflagration fracturing was developed using this model to simulate the fracturing process in vertical wells within a low-permeability sandstone reservoir. Under impact loading, a fragmented zone is formed in the rock, and the effective transformation volume of the reservoir is determined by calculating the volume of this fragmented zone. This provides a new evaluation method for assessing fracturing effectiveness, which is then used to evaluate the impact of deflagration fracturing. The results indicate that under impact loading, the deflagration reach ranges from 0.21 to 4.2 m, with a nonlinear relationship between the drug volume and the deflagration reach. As the drug volume increases, both the deflagration reach and the fracturing reforming effect are significantly improved. Furthermore, the drug volume is closely correlated with energy release: larger drug volumes result in greater energy release, larger reforming volumes in the reservoir, and improved fracturing outcomes. Consequently, production capacity is enhanced.