Going forward, limiting greenhouse gas emissions and reducing water usage in oil sands upstream operations is essential to meeting regulatory requirements and a pre-condition for the social license to operate. As Oil Sands Industry exhausts its best quality rich pay and gradually move into producing bitumen from marginal quality assets with thin pay zones, SAGD performance will deteriorate with higher steam to oil ratios. In this paper, Enhanced Convective Solvent Extraction (ECSOLVEX) process is described to apply to such reservoirs.
ECSOLVEX predominantly uses a pure solvent which is injected into the reservoir at or above its dew point temperature. Injection and production wells are placed some distance apart in the same lateral plane. Sidetracks from injector well to close proximity of the producer well allow a solvent chamber to extend to the inter-well region. The process is primarily gravity driven with a mild convective gradient from injector to the producer well. A solvent chamber is established along the side track lateral, which grows parallel to the injector and producer wells. Water production is limited since it is a solvent driven processthat would result in a reduced footprint for the surface oil water separation facility.
Simulation results show that each side track creates its own drainage chamber which performs independently of other drainage chambers till they merge, thus the production performance of this process is a function of the number of sidetracks drilled. As an example, with propane as the solvent, production rates can be doubled that of SAGD if sidetracks are drilled every 100m. The energy consumption and associated emissions of such a process would be 70% less than SAGD. The performance can be further improved by localized heating in the proximity of the producer well.
ECSOLVEX process concept provides the opportunity for economic recovery from pay zones which are not thick enough for traditional SAGD process to operate. It demonstrates significantly lower energy consumption as compared to SAGD, leading to a lower carbon footprint and has the potential to reduce the size of the oil water separation facility.