Performance Optimisation of Low‐Damage Foam Fracturing Fluid System in Unconventional Reservoirs

Foam fracturing fluid is a prospective substitute for water‐based fracturing fluid, with the potential to effectively mitigate the adverse effects associated with unconventional reservoirs. However, the greenhouse effect caused by CO 2 accumulation and CO 2 utilisation represents a significant challenge, limiting the fracturing efficiency of unconventional reservoirs. The aim of this investigation is to optimise the formulation of foam fracturing fluids using CO 2 fluid and analyse the fracturing capability of foam fluids. Specifically, this paper first built a fracturing model based on extended finite element and the impact of different factors on the fracturing capacity of foam fracturing fluid with CO 2 fluid was analysed. In addition, the performance evaluation coupling platform is employed to elucidate the mechanism underlying the parameter changes of foam fracturing fluids. The results indicated that the foam stabilisers serve to stabilise of foam fracturing fluid, thereby reducing the CO 2 fluid filtration and improving the fracturing efficiency of reservoir fractures. Furthermore, the stability, apparent viscosity and filtration of CO 2 fracturing fluid are all enhanced by reservoir pressure, whereas an increase in reservoir temperature and salinity has the opposite effect. The reservoir pressure changes the apparent viscosity and filtration volume of the foam fracturing fluid by −16 and 0.42 mL, respectively, while the reservoir temperature reduces the above two parameters by 21 mPa·s and +0.23 mL. The vacuole stability and electron distribution in the diffuse double layer represent significant factors that influence the efficacy of foam fracturing fluids, and this paper could provide a basic data support for the development of foam fracturing fluids in unconventional reservoirs.