The pressurization effect of jet fracturing using supercritical carbon dioxide

摘要

Hydro-jet fracturing is a unique hydraulic fracturing method, and has been recognized worldwide as an effective well-stimulation method for oil and gas production. However, because of controversy about the method's impact on water consumption and environmentally quality, hydraulic fracturing faces increasing restrictions. The demand for decreased water usage has promoted research on the use of nonaqueous fracturing fluids. In particular, the idea of using supercritical carbon dioxide (SC-CO2) fluid has attracted a lot of interest. Using SC-CO2 as a fracturing fluid is more effective and has significant advantages compared with water-based fluids. The unique properties of the SC-CO2 fluid facilitate fracture propagation, formation of complex fracture networks, and elimination of flow blockage in the rock matrix and pores. Therefore, the SC-CO2 jet fracturing technique may effectively enhance oil and gas recovery. Similar to hydro-jet fracturing, the pressurization effect in the perforation tunnel is a key precondition for successful jet fracturing with SC-CO2. This study investigated these effects using numerical simulations and experimental studies. Our results show that the pressurization effect during SC-CO2 jet fracturing improves with an increase in pressure difference, ambient pressure, nozzle diameter, and fluid temperature. However, pressurization becomes weaker with increasing casing hole diameter and annulus spacing. Comparing SC-CO2 and water jet fracturing pressurization effects suggests that using SC-CO2 jetting has advantages over water jet fracturing under in situ reservoir conditions. As the working depth increases, SC-CO2 jet fracturing achieves better pressurization than the water jet. The novel approach in our preliminary study begins to prove the feasibility of applying SC-CO2 jet fracturing to leverage unconventional resources. (C) 2015 Elsevier B.V. All rights reserved.