The Rheology Of Carbon Dioxide Foam Fracturing And Fracturing Design Model Study

When fracturing the above-mentioned formation, the common hydraulic fracturing always fails or the stimulation effect is not satisfactory, therefore, these formations must be treated by foam fracturing. Due to the small formation damage, swift flowback, low leakoff coefficient, high viscosity, small friction loss and good proppant-carrying capacity, foam fracturing is widely used in above-mentioned formation.But, the theory research of the foam fracturing falls behind the field application, thus it restricts the application of the foam fracturing. The lack of the theory research mainly expressed the following several aspects: there is no agreement on the reheology of the foam fracturing fluids under the circumstance of room temperature and pressure, not to mention the case of high pressure and high temperature; there is no fracture propagation mode for the foam fracturing. Therefore it is necessary to study-the reheology of the foam fracturing fluids under high temperature and pressure and the fracture propagation mode for the foam fracturing.Based on the formers' research, following four aspects are studied in this paper and corresponding conclusions are made.1. Studied the reheology of the foam fracturing fluids under the circumstance of high temperature and pressure by virtue of, the large-scale, high-parameter foam fracturing fluids flow loop in XI'AN Jiao Tong University. Studied the effect of the parameters such as shear rare, foam quality, temperature, pressure et al on the rheological parameters. Fitted the rheological parameters expressions for the CO₂ foam fracturing fluids based on guar fluid. And the following conclusions were concluded: (1) when the foam quality is smaller than 0.9, the foam fluid can be depicted by the power law model; when the foam quality is larger than 0.9, the foam fluid can be depicted by the Bingham model. (2)CO₂fracturing fluid is a shear thinning and temperature thinning fluid. (3) The effect of the foam quality and temperature is large and the effect of the pressure is little. (4) As the foam quality increases, n decreases, k increases; As the temperature increases, k decreases, n increases.2. Studied the flow of the CO₂ foam fluids in the wellbore and established the hydrostatic column model and the friction calculation model for the CO₂ foam fluids. Calculation showed that: as the foam quality increases, the friction loss along the tubing increases, but the larger the foam quality is, the smaller the increment is; the smaller the foam quality is, the larger the increment is.3. Established a pseudo-3D fracture propagation model for the foam fracturing fluid behaved as power law model. The model is mainly made up of pressure drop equation in the fracture, width equation, height equation, continuing equation, state equation. The effect of friction was considered when calculating the wellbore temperature field. Analyzed the effect of the foam quality, flux et al on the fracture dimensions. Calculation showed that temperature has great effect on the CO₂'s state...