Abstract
This paper discusses the energy-efficient operation of Fast-steam-assisted gravity drainage wellpad system in the presence of reservoir heterogeneity, different well constraints, and lateral flux communication between adjacent steam chambers. Fast-steam-assisted gravity drainage incorporates cyclic steam stimulation in an unrecovered area between steam-assisted gravity drainage wellpairs, and the well constraints of the wellpad system (including the injection pressure and steam injection rate at the injectors, bottom hole pressure, surface liquid rate, and steam rate at the producers) are simultaneously optimized to accomplish the minimum cumulative steam-to-oil ratio for a given bitumen recovery constraint. The higher injection pressures of the cyclic steam stimulation can result in greater efficiency by pushing the diluted fluid mixture to the steam-assisted gravity drainage producers through the cross-over zone between the steam chambers. At an early stage, a greater amount of steam should be injected through the cyclic steam stimulation work, and at the late stage, a lower injection pressure is needed to use the latent heat. The positive effects of the cyclic steam stimulation at the edges of the steam-assisted gravity drainage steam chambers are concentrated at localized flow paths where the lateral flux transport occurs due to spatial heterogeneity. A sensitivity analysis shows that the injection pressure and the steam rate produced for the steam-assisted gravity drainage wellpairs influence the energy efficiency of the entire thermal operation when compared to other configurations.
Highlights
The heat-unreached zone between the steam-saturated areas results in inefficiency during production, notwithstanding that the steam-assisted gravity drainage (SAGD) process is technically marketable to recover extra heavy oil
All trends of cumulative steam-to-oil ratio (cSOR) for 500 cases used in the particle swarm optimization (PSO) are derived from 1.46 to 2.21 only if considering minimizing cSOR while the maximum oil production is about 483,715 m3 (1⁄4 3,042,232 bbl; about three million barrels) regardless of considering the energy efficiency
The reservoir heterogeneity influenced the unequal growth of the steam chamber, localized lateral flow interference, and generated irregular unrecovered areas
Summary
The heat-unreached zone between the steam-saturated areas results in inefficiency during production, notwithstanding that the steam-assisted gravity drainage (SAGD) process is technically marketable to recover extra heavy oil. The cyclic process accelerates the lateral growth of the steam chamber and thereby increases the thermal efficiency during the production period This combined process can be divided by different CSS start-up times, and the operating cycles of the steam injection, soaking, and production, which are known as hybrid SAGD (Coskuner, 2009; Ghanbari et al, 2012; Li et al, 2011; Xu et al, 2014), Fast-SAGD (Jeong et al, 2013; Kamari et al, 2015; Polikar et al, 2000; Sarapardeh et al, 2013; Shin and Polikar, 2006, 2007), and wedge well technology (Manchuk and Deutsch, 2013). To obtain the energy-efficient operation of Fast-SAGD, the objective function is to minimize cumulative steam-to-oil ratio (cSOR) in the condition of a constraint of bitumen production volume through CSS. The parameters are the well constraints of the Fast-SAGD operation and the response is cSOR to examine the energy efficiency
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