Experimental investigation of water flooding characteristics and residual oil distribution in filled attic caves reservoir

Abstract

Attic karst cave is one of the most common fractured-vuggy structure in Tahe oilfield. In this study, a typical attic-shaped cave was extracted from the geological section of Tahe Oilfield. Under the guidance of similarity criteria, physical experiment models of attic karst cave reservoir filled with oil-wet and water-wet filling medium were designed and fabricated using coated resin sand and cemented quartz sand. Water flooding experiments at different injection rates were carried out using the attic karst cave model filled with filling medium of various wettability. The water flooding characteristics and distribution law of residual oil in the different models were determined by analyzing oil displacement performances and the dynamic production curves. Results showed that when the filling medium is water-wet, water injection rate has a trivial impact on the residual oil distribution pattern. While for the oil-wet media filled situations, the lower the injection rate, the lower the swept area. However, at high injection rates, the spread scope is large but the displacement efficiency remains relatively low. In addition, it was noted that the difference in the wettability of the filling medium caused a difference in the location of the residual oil.