Experiments and Analysis of Heavy-Oil Solution-Gas Drive

Abstract

Summary We provide a general framework for interpreting heavy-oil solution-gas-drive experiments. Evolution of the gas phase below the thermodynamic bubblepoint is investigated with dimensionless scaling groups, mechanistic modeling, and experiments. Carefully planned and monitored depletion experiments are conducted to evaluate pre- and post-critical gas-saturation behavior. In-situ phase saturations are measured with X-ray computerized tomography (CT) scanning. These data are used in conjunction with differential-pressure measurements along the core to obtain phase mobilities. It is demonstrated that most laboratory heavy-oil-depletion experiments show nonequilibrium effects that depend on the oil-phase viscosity and depletion rate. Factors leading to the coalescence of gas-bubble clusters and development of bulk gas flow are illustrated with examples, along with an empirical correlation for critical gas saturation (Sgc). Examination of field-pressure gradients and flow rates suggests that dispersed gas flow may occur close to the wellbore or near wormholes, if present.