LAUSR

Abstract When working over wells with low-pressure reservoirs, loss of workover fluids into the reservoirs has been a problem that must be resolved. To resolve this problem, on the basis of theoretical knowledge and application characteristics of foamed gels, we developed a strong, stable, nanocomposite foamed gel as a temporary plug. The gel has high stability and low density and exhibits low fluid loss compared with traditional workover fluids. The foamed gel comprises 0.5%wt to 0.7%wt partially hydrolyzed polyacrylamide, 1.4%wt foaming agent, 0.25%wt nanosilica, 0.03%wt to 0.05%wt metallic-ion crosslinking agent, and 0.02%wt deoxidant. The temporary plugging simulation experiment shows that, for the core with low permeability, pressure drawdown across cores under a 15 MPa positive pressure differential was less than 1.2 MPa in 60 min and the rate of filtration of fluid through the cores was almost zero. The result shows that the nanocomposite foam gel has a certain capacity for compression and a low filtration rate and can effectively plug reservoir rocks temporarily. Therefore, the prosed foamed gel offers good application prospects in preventing loss of workover fluids in low-pressure reservoirs. Graphical Abstract