Experimental evaluation of self-generated heat-enhanced fracturing fluid for low-temperature and low-pressure shallow reservoirs

The Chang 6 sandstone reservoir in the Ordos Basin of China is a typically shallow low-permeability tight sandstone oil reservoir, characterized by shallow burial, low temperature, and low formation pressure. Traditional water-based guanidine gum fracturing fluid shows incomplete degradation under such low temperature (30 °C) and low formation pressure (2.6–3.0 MPa), leading to suboptimal reservoir performance. The paper employs NaNO2 and NH4Cl to generate heat and increase pressure in a novel self-generated heat fracturing fluid system, based on the chemical reaction mechanism. The experimental evaluation indicates that the system combines the merits of water-based and foam fracturing fluids, and the sand-carrying performance is nearly 1.5 times that of the conventional guanidine gum fracturing fluid. The flowback rate of this fracturing fluid is elevated by approximately 10.56% in contrast to guanidine gum fluid, and the formation damage rate is decreased from 21.68% to 12.10%. The fluid infiltrates the formation and heats up automatically, facilitating a quicker and more comprehensive breakdown, with the temperature rise exceeding 30 °C. The breakdown time is confined within 1–4 h, and the viscosity remains beneath 5 mPa s. The increase in formation energy induced by N2 in the near-wellbore area can also play a role in minimizing formation damage and enhancing reservoir productivity. By effectively controlling the impact of cold formation damage and the water lock phenomenon, this innovative method not only boosts the overall value of the formation but also optimizes production efficiency. Moreover, it offers a sustainable solution for maximizing recovery from complex oil and gas reservoir, thus contributing to the long-term feasibility of hydrocarbon resources. This comprehensive technical progress highlights its potential as a revolutionary strategy for reservoir development and management in various geological conditions.