Effects of Gravity, Foaminess, and Pressure Drawdown on Primary-Depletion Recovery Factor in Heavy-Oil Systems

Abstract

Summary The unusually high primary recovery factors (RFs) observed in numerous heavy-oil reservoirs are often attributed to foamy oil flow (i.e., the non-Darcy flow involving formation and flow of gas-in-oil dispersion). It occurs when the wells are produced aggressively at high drawdown pressures that led to conditions in which the viscous forces become sufficiently strong to overcome the capillary forces in pushing dispersed bubbles through pore throats. The role of gravitational forces in generating such dispersed flow has not been studied adequately. This work was intended to evaluate the contribution of gravitational forces in primary depletion of heavy-oil formations under foamy flow conditions. Primary-depletion tests were conducted in a 200-cm-long sandpack that was held in either horizontal or vertical orientation. The results of horizontal depletion tests were compared with the depletion tests conducted with the sandpack in the vertical direction. Vertical depletions showed better recoveries at slower depletion rates compared with horizontal depletions. The RFs of both horizontal and vertical depletions were correlated against the average drawdown pressure available to move the oil. It was found that the RF shows a strong dependence on the average drawdown pressure. It was also found that the curve of RF vs. average drawdown pressure moves slightly toward higher recoveries in the presence of an added foaming agent (i.e., with increased oil foaminess).

Experimental study and new three-dimensional kinetic modeling of foamy solution-gas drive processes

“…Note that the production of foamy oil continues although free gas starts to flow at this pressure. This finding is consistent with the observations reported by Alshmakhy and Maini 16 .…”

“…They discovered that overburden pressure influences the features of flowing gas bubbles, critical gas saturation and oil recovery. Alshmakhy and Maini 16 reported an experimental study of the effect of gravity on oil recovery. They determined that gravity has a beneficial effect on recovery in some conditions because it increases the mobilizing force that is exerted on gas bubbles and encourages foamy oil flow.…”

Simulating Geological Features of Torrential Deposits

“…As initial parameters for constructing the structural surface along the stratigraphic formation top АC13 strata surface was constructed on seismic grid by reflecting horizon "M", and stratigraphic tagging by drilled holes [7]. Structural surfaces along the top and bottom of the collector below embedded strata were created by the method of geological constructing a horizon by adding the isochores from the above surface along the stratigraphic strata roof and outcome data of the well findings (well log interpretation results) [6].…”

Experimental Study and Mechanism Analysis of the Effect of Oil Viscosity and Asphaltene on Foamy Oil

“…Researches show that the formation of foamy oil is closely associated with pressure depletion rate, solution gas-oil ratio, temperature, oil viscosity, and oil components (especially asphaltene) [13][14][15][16][17][18][19]. Pressure depletion rate determines the performance of solution gas drive for heavy oil reservoirs.…”

“…However, some researchers found viscosity not to be the intrinsic reason for foamy oil through comparing mineral oil and crude oil results [16]. Asphaltene is well known to cause an increase in viscosity for heavy oil, and, as a surface-active substance, it can be adsorbed onto the oil-gas interface and improve the stability of the micro-bubble.…”