An Investigation into Boosting Pressure in the Cavity while Hydra-Jet-Assisted Fracturing: An Improved Model with Insightful Sensitivity Analysis

Hydraulic fracturing has been widely used in the petroleum industry for exploiting tight and ultra-tight formations. Although conventional hydraulic fracturing techniques have advanced significantly over time, it is still challenging to achieve separate intervals within multilayered formations, target the right layers and accurately fracture in succession. Hydra-jet-assisted fracturing, which involves boosting pressure in the cavity behind the casing to enable successful fracture initiation, is a technique often practiced to overcome this. However, there exists limited research regarding the pressure field within the cavity; therefore, this study aims to establish a mathematical model for predicting boosting pressure in the cavity under various reservoir conditions. In this paper, the authors present a numerical model to investigate the effects of nozzle differential pressure ratio of nozzle diameter to cavity diameter, annulus pressure and cavity length on boosting pressure. It is observed that the boosting pressure increases linearly with nozzle differential pressure and diameter ratio, respectively, while retaining other parameters as constant. However, simulations also indicate that annulus pressure and cavity length have minimal effect on the boosting pressure. In addition, the relationship between the boosting pressure coefficient and dimensionless standoff distance is also developed for specific diameter ratios, along with an insightful sensitivity analyses. A mathematical model is established to predict the final boosting pressure at different diameter ratios. As a result, this advances understanding of the design of treatment parameters in hydra-jet-assisted fracturing. Furthermore, this investigation is another step forward toward the global application of hydra-jet fracturing technology in developing deeper and layered tight gas sands.