Significance of Advanced Spontaneous Imbibition, and Wettability Alteration on Enhanced Oil Recovery (EOR) in Tight Oil Reservoirs

Abstract

Depletion of fuel energy resulted from unconventional gas resources cause scientists to put more efforts on searching for unconventional oil and gas resources such as shale gas and tight sand reservoirs. To increase efforts in this spontaneous imbibition has stood studied for the purpose of tight oil reservoir development. Different oil field explored have shown the soaking effect during oil production depends on imbibition. Significant amount of oil has been recovered by soaking cogency after hydraulic fracturing through fracturing fluid. For the reason of studying wettability and advanced spontaneous imbibition significance with the influencing aspects in tight oil reservoirs, imbibition and wettability laboratory tests from various tight core samples with porosity and permeability range from 6.4 to 14.1% and 0.023 to 2.54 mD respectively were conducted. In this Study first, weight change by spontaneous imbibition of a core sample in each sample set in the oil with other contained in brine were measured periodically. Thereafter, the oil-saturated core samples were placed in brine to determine the amount of expelled oil droplets and measure recovered oil volume with respect to time. From the result it can be seen that the spontaneous imbibition and subsequently expelling the oil by water will occur without depending whether it is water-wet or mixed-wet tight cores. The wettability alteration as a driving force has insignificant effect on imbibition recovery and contact angle for the water-wet core compared to that of the mixed-wet or oil-wet core. These results indicate that only hydrophilic part of the pore network which were oil-saturated initially can be reached by water.