Convective heat transfer of CO₂ foam fracturing fluid under downhole conditions

Foam fracturing is an important technology in the development of low permeability oil/gas reservoirs. The heat transfer characteristics of foam fracturing fluid are directly relevant to the calculation of pressure drop in the well, the optimum choice of fracturing parameters and the accurate evaluation of fracturing results. CO₂ foam fracturing fluid behaves as a non-Newtonian fluid. The convective heat transfer characteristics of CO₂ foam fracturing fluid were experimentally investigated on the newly constructed large-scale test loop under downhole conditions with CO₂ in supercritical state, the pressure up to 40 MPa. From the test data, corresponding correlations for convective heat transfer were obtained and the influences of pressure, temperature and flow rate were also studied. The convective heat transfer coefficient increased with the increase of temperature and flow rate, while the effect of pressure was much more complicated. In most cases, with the increase of pressure the coefficient tended to decrease.