Laboratory experiment study on weakly connected crack sealing system

Abstract

According to the difference of matrix displacement pressure and crack re-tension pressure in fractured reservoirs, it is difficult to develop reservoirs. The gel prepared by using water-soluble phenolic resin as cross-linking agent seals weakly connected cracks. In this paper, the gelation properties, injectability and plugging properties of the gel were studied. The results show that the gel formula was 0.5w% polymer + 0.5w% water-soluble phenolic resin + 0.2w% catalyst NH4CI, the gelation time was 48h, the elastic modulus after gelation reached 16 Pa, and the long-term stability was good without obvious dehydration. The gelation forming liquid had a viscosity of less than 200 mPa·s in the oil pipe, and the highest flow resistance was 3.77×10−4 MPa/m; in the reservoir, the pressure gradients of slit widths of 1.0 mm and 0.5 mm (0.1 mL/min) were 0.014 MPa/m and 0.107 MPa/m, respectively. The results of the physical model test show that the breakthrough pressure ladders of the gel in the cracks of different slit widths (1mm, 0.5mm and 0.3mm) were 4.152MPa/m, 4.872MPa/m and 7.160MPa/m, respectively. The 0.5mm slit width could be stabilized for 24h at 1MPa and 2MPa, and the gel had a certain sealing effect after the breakthrough.