Polymer-Enhanced Foam Flooding for Improving Heavy Oil Recovery in Thin Reservoirs

摘要

Oil reserves of the thin heavy oil reservoirs are estimated to be over 400 billion barrels. The recovery factor of water-flooding in these reservoirs is as low as 10-20% due to the high oil viscosity and correspondingly unfavorable mobility ratio. In addition, the commonly used thermal recovery methods are also unsuitable in such formations due to the significant heat loss to the adjacent formations. Thus, it is urgent to find an efficient and economic enhanced oil recovery (EOR) method to maximize the recovery factors in the thin heavy oil reservoirs. In this study, the feasibility of polymer-enhanced foam (PEF) flooding for the thin heavy oil reservoirs is investigated using the micromodel and core-flood experiments. The micromodel experiments show that foam quality has significant effects on the resistance factor and heavy oil recovery of the PEF flooding, where the displacement front of a low-quality foam case is more even than that of a high-quality foam case and surfactant-polymer (SP) flooding case. Core-flood tests further reveal that there is an optimal slug size under the experimental conditions, and the heavy oil recovery of PEF flooding is 23.9% higher than that of SP flooding when using the same slug size. Finally, a field-scale reservoir simulation is conducted, and the results show that after initial water-flooding in thin heavy oil reservoirs, the recovery factor achieved by the PEF flooding is 11.7% higher than that of the SP flooding and 21.4% higher than that of the continuous water-flooding process.