Scaled Physical Model Experiments to Characterize the Gas-Assisted Gravity Drainage EOR Process

摘要

The year 2006 marks the first time the gas injection EOR production has surpassed that of steam injection processes in the US, signifying the growth of gas injection as a mature technology. In order to control the rising tendency of injected gas in horizontal floods, the water-alternating-gas (WAG) process has generally been the mode of operation in many fields. In spite of its wide application, the WAG process has not lived up to its expectations with reported recoveries in the range of 5-10% OOIP. In order to improve recoveries, we have been attempting to develop the gas-assisted gravity drainage process at LSU. This paper summarizes the effort of conducting scaled physical model experiments in a visual glassbead-packed model aimed at discerning the influence of some scaled dimensionless parameters, such as the capillary number, Bond number and gravity number, on the GAGD process performance. A 2-D physical model, of 16" X 24" X 1" dimensions, packed with uniform glass beads, was used to conduct visual experiments. These experiments were so designed as to mimic the dimensionless parameters observed in some field projects. The secondary mode GAGD floods yielded recoveries up to 80% OOIP. Additionally, the recoveries displayed a semi- logarithmic relationship with gravity number (ratio of gravity to viscous forces). Interestingly, this relationship was observed to hold good for the high-pressure GAGD corefloods and even the field production data from gravity-stable gas injection projects conducted in pinnacle reefs. A multi-variable regression analysis of the laboratory as well as field data indicated that the Bond number, being the ratio of gravity to capillary forces, had a greater influence on GAGD performance than other parameters. In addition to the observed high recoveries, our attempts to relate the model run times to field project durations, through dimensionless time considerations, have indicated reasonably good rates of production when GAGD process is implemented in field projects.