Some researchers report that relative permeabilities are dependent on temperature, and provided impact rules 5– 20, but others concluded that temperature has little effect on relative permeability or that no direct influences exist 21– 29. Every researcher has drawn their own conclusions in more than 50 years of investigation, and two conflicting statements have emerged. In the 1960s, measurements of relative permeability with increasing temperature began to appear in thermal oil recovery studies. Moreover, controversy still surrounds the issue of whether relative permeability is dependent or not on temperature no consensus has yet been reached. The authors of these studies did not consider dissolved gas in oil and salinity in water under the conditions of practical reservoirs, which may create certain deviations upon oilfield application. At present, numerous related experiments on heavy oil and water relative permeability are based on displacements of dead or refined oil by distilled water. Heavy-oil reservoirs are mainly thermal recovery reservoirs thus, heavy oil is very sensitive to temperature hence, researching change regulations of oil-water relative permeability of heavy oil for differing temperatures is becoming extremely significant 1– 4. Inputting variables for numerical reservoir simulation models and characterizing underground flow behavior of immiscible fluids are two very critical applications of relative permeabilities. Relative permeability to heavy oil and water is one of the most important parameters of production and prediction in oilfields. The water-wettability of rocks is heightened and overall relative permeability curves shift to the right with increasing temperature furthermore, two-phase flow area becomes wider and both oil and water relative permeability increases apparently, but the increase ratio of water is less than that of oil. As temperature increases, irreducible water saturation linearly increases, residual oil saturation performs a nonlinear decrease, and water saturation exhibits a nonlinear increase at equal-permeability points. Study results suggest that relative permeability is high to oil phase and is very low to water phase, and fluid flow capability is extremely imbalanced between oil and water.
Both water and heavy oil in cores were reconfigured under the consideration of actual reservoir conditions. Measurements of relative permeability were based on one-dimensional core-flow simulated systems using an unsteady-state technique at different temperatures, and then impact rules of temperature dependency were discussed. A heavy-oil sample derived from a block of Venezuelan oil was used to investigate effects of temperature on relative permeability to oil and water.
0 kommentar(er)
