A model for evaluating fracture leakage based on variations in bottom-hole temperature and pressure during the fracturing process

Abstract

During the large-scale fracturing and exploitation of unconventional reservoirs, artificial fractures progressively widen in reservoirs with natural fracture development, which is highly prone to fracture leakage between segment clusters, thereby impacting the complexity of fracture networks. Nevertheless, the existing research on the evaluation model of fracture leakage in the fracturing process is limited and lacks precise predictive capabilities. The model has been developed to assess the variations in bottom hole pressure and bottom hole temperature during fracture extension by considering the combined effects of pressure loss, temperature exchange, along-track drag, static column pressure, and integrated heat transfer among the fracturing fluid, tubing wall, annulus, casing wall, and formation. The model is capable of evaluating the occurrence of fracture leakage by analyzing the extent of temperature and pressure variations at the base of the wellbore. The study findings compare the temperature and pressure data from 14 out of 144 actual fracture leakage sections of three wells monitored in an oilfield, and it is believed that the situation of fracture leakage can be identified when the predicted temperature changes fall within the range of −2.95 °C–7.53 °C, and the predicted pressure changes range from −0.87 MPa to 6.55 MPa. The model yields an average error of 4.09% for pressure and 5.73% for temperature. Moreover, the model demonstrates high overall prediction accuracy, which holds significant implications for promptly identifying inter-segmental fracture leakage and facilitating the efficient development of oil and gas fields.