Experimental investigation on improving steam sweep efficiency by novel particles in heavy oil reservoirs

Abstract

Steam channeling, an inevitable and severe problem in the steam injection process, seriously affects the oil production and ultimate recovery of heavy oil reservoirs. In this paper, a novel low-temperature thermo-expandable graphite (TEG) particle, prepared by the chemical oxidation method, was firstly used to solve the universal problem of steam channeling. The functional groups, microstructure, and morphology changes of TEG particles were characterized during intercalation and expansion process. A series of experiments were performed to study the expansion capacity, suspension system, plugging and injection performance of TEG particles. Based on this, oil displacement experiments were conducted to study the effect and mechanisms of the multi-stage plugging technique using the optimized particle system. The results showed that TEG particles had an initial expansion temperature of 140 °C. The expansion volume can reach more than ten times under the condition of high-temperature steam, which was much smaller than that under dry conditions. The expansion volume increased with the increase of particle size and steam temperature. TEG particles with soft property can deform and migrate through pores and throats, and expand into a worm-like morphology under high-temperature steam, directly blocking the pores and throats. The plugging and injection performance of the TEG particle system under different influencing factors were evaluated. And the multi-stage plugging technique can effectively plug the high permeable channels where steam channeling occurs step by step to divert the subsequent steam into the unswept area, thus significantly improving the oil recovery. This article provides a novel plugging agent that is expected to be an excellent substitute for conventional plugging agents and an effective method to solve the problem of steam channeling in heavy oil reservoirs.