Surfactant Huff-n-Puff Application Potentials for Unconventional Reservoirs

Abstract

Abstract Improved Oil Reocvery (IOR) technologies may offer a new strategy to improve the initial production (IP) and slow the production decline from oil-rich shale formations. Early implementation of chemical IOR technologies largely have been overlooked during strategic planning of unconventional reservoirs. The purpose of this study is to improve understanding of the dynamic processes of oil displacement by surfactants and to investigate mechanism of how surfactants extract oil. A successful conventional surfactant "huff-n-puff' treatment is described with a focus on any relationship between increased oil production and the surfactant soaking period. Surfactant chemistry has been considered as one of a few ultimate IOR solutions. Despite being well proven as effective chemicals to recover oil from convenetional reservoris, surfactants commonly are used in hydraulic fracturing of unconventional reservoris are just to promote flow back of the injected aqueous fluid over a relatively short time frame. In order to better understand the functionality of surfactants for obtaining favorable oil interaction with both the stimulation fluid and rock matrix, a specifically-designed "oil-on-a-plate" (OOAP) setup and procedure is employed to examine the penetration of surfactant into the oil-film that is adhereing to a solid surface. In addition to the well-recognized spontaneous imbibition and surface wettability alternation processes, surfactant also can gradually penetrate and mobilize oil droplets, resulting in improved oil recovert. If properly selected and designed, the surfactant additives in stimulation/fracturing fluids could have multi-functions towards improving both IP and the longer-term oil production. Besides serving as a demulsifier and flowback enhancer to boost IP, the surfactants could continuously lift-up and mobilize adsorbed oil to increase recoverable oil in place.