Research on New Polymer Microsphere Gel for In-Depth Profile Control and Its Application in Low Permeability Reservoir

Abstract

Polymer microsphere gel (PMG) has been widely used in deep profile control oilfield because of its outstanding profile control and displacement performance, as well as the excellent simplicity of the site mixing fluid and injection process. Scanning electron microscopy (SEM), laser particle size analyzer and sand-filled tube model are used to evaluate the apparent characteristics, particle size distribution and plugging performance of PMG. It turns out that PMG apparent viscosity is 2 mPa.s–6 mPa.s. Under the condition of shear rate is 0–700-s, viscosity first declines quickly and then increases gradually, viscosity recovery rate is above 61%, eventually the viscosity remains steady. The initial particle size of the microspheres is in the state of normal distribution for 1 μm–20 μm, and the hydration expansion ratio of the microspheres reaches up to 10 times under the condition of mineralization degree of 65.8 g/L and temperature of 55 ℃ for about 30 days. The longer the hydration time, the easier the microspheres to form clusters. Hydration expansion and adhesion cluster are the major mechanisms of in-depth profile control. Resistance factor of microspheres is 1.64–2.42, residual resistance factor is 5.13–7.61, and plugging rate is 80.5%–86.9%, which are tested in three sand-filled tubes with length of 0.5 m and brine-tested permeability of 52.91–57.85 mD. The on-site test shows the average injection pressure increases 0.13 MPa/1000 m in 6 wells. Barrel of oil per day of corresponding production wells goes up from 27.4 t/d to 30 t/d, water cut goes down from 75.3% to 71.3% in 29 profile control wells. Its technical adaptability turns out to be outstanding.