Experimental and numerical simulation studies on sweep efficiency in electrical heating-CO2 assisted SAGD for heavy oil reservoirs with interbeds

Abstract

Dual horizontal well steam-assisted gravity drainage (SAGD) technology is an effective method for developing heavy oil reservoirs. However, heterogeneous factors often result in uneven steam chamber development that such as interlayers in the reservoir, which ultimately lower the sweep efficiency. This paper focused on electrical heating-CO₂ assisted SAGD in Xinjiang oilfields in China to enhance both sweep efficiency and overall recovery in heavy oil reservoirs. It was investigated that the mechanisms and technical potential of electrical heating and CO₂ in the preheating initiation and development production processes of SAGD. Three-dimensional physical experiments and numerical simulations were used to determine the best preheating methods and key parameters. The results showed that the intermittent heating and intermittent CO₂ injection yielded the best transfer effects and sweep outcomes. Electrical heating induces micro-fractures in interbeds to establish oil drainage channels, while CO₂ enriches at the edges of the steam chamber, dissolving to reduce viscosity and expanding the operational range by 6.8 %. The integrated technology achieves an ultimate recovery rate of 62 %, representing a 23.6 % improvement over conventional SAGD, alongside a 9.1 % reduction in cumulative steam injection and an enhanced cumulative oil-to-steam ratio of 0.35, with significantly more uniform residual oil saturation distribution. By optimizing the vertical uniformity of steam chamber expansion and extending the stable production period, this approach provides an innovative pathway for efficient development of heavy oil reservoirs with interbeds.