Abstract:

Sand production and high water content in oil wells are two major challenges that restrict high and stable production in loose sandstone reservoirs. In this paper, nano SiO₂, coupling agent triethoxysilane, phenolic resin and n-octanol were used to synthesize the main agent SCA-2. Hexamethylenetetramine and vinyl carbonate were selected to prepare the curing agent YGA-1, which was then compounded with SCA-2 to develop a sand fixation and water plugging system. Firstly, single-factor experiments were conducted to determine the optimal concentrations of SCA-2 and YGA-1, subsequently, the system’s sand fixation and water blocking performance were evaluated. Finally, a pilot test was carried out in the mining site. Experimental results showed that the optimal formula composition of the system was 10% SCA-2+5% YGA-1. The gelation time of the system was 180 minutes and the viscosity after gelation could reach 108.4 mPa·s. When the dosage of the drug system was 0.6 PV, the sand production rate remained below 0.08%. Dual-tube parallel experiments showed that the sand fixation and water plugging system had a water flow channel plugging rate of 87.5%, while the oil flow channel plugging rate was only 11.3%, indicating minimal damage to the oil-bearing reservoir. The field test showed that after the measures taken in Well M of X oilfield, the sand free oil recovery period exceeded 360 days, the water content decreased by 5.0% and the cumulative oil production increased by 7 092 m³. This study provides new ideas for efficient development of loose sandstone reservoirs.

Key words: solidify sand and block water, loose sandstone, formula optimization, performance evaluation, field test