Experimental Study of Foam Flow in Fractured Oil-Wet Limestone for Enhanced Oil Recovery

Our objective was to study foam flow in fractured, oil-wet carbonate rocks and determine if foam may be a viable enhanced-oil-recovery (EOR) agent in such reservoirs. We present experimental results in fractured carbonate rock and show effects of wettability on oil recovery when using foam. Oil recovery by water, surfactant, or gas injection exhibited low recovery, less than 10% of original oil in place (OOIP). Oil recovery during injection of pregenerated foam was improved significantly, with up to 78% of OOIP produced. Foam reduced the gas mobility in the fractured rock, increased differential pressure, and diverted flow into the oil-saturated matrix. However, a significant amount of foam injection was required for the additional oil recovery. Generation of foam in-situ was weak in the smooth-walled fractures, and no fluid diversion from the fractures with additional oil recovery was observed. On the basis of the experimental results, mechanisms for foam collapse in the fracture are discussed and possible steps to improve recovery are outlined.