تأثير استخراج نفت به كمك بخار (VAPEX) بر ضريب بازيافت نفت

Extracting unconventional heavy oil an‎d bitumen from shallow reservoirs presents a significant technical challenge for the petroleum industry. In formations such as the 91-meter reservoir analyzed in this study, conventional thermal extraction methods, specifically vapor -assisted gravity drainage (SAGD), often prove inefficient due to excessive heat loss to overlying rock layers an‎d the risk of mechanical failure of the insulating rock under high vapor injection pressure. As a sustainable, non-thermal alternative, vapor-assisted extraction (VAPEX) has emerged as a viable solution, utilizing molecular diffusion instead of thermal energy to move the bitumen. This research presents a comprehensive numerical study of the performance of the VAPEX process using propane as the gaseous solvent. Using the CMG STARS simulation suite, a high-resolution 3D Cartesian model consisting of 1950 active grid cells was constructed to simulate a 34-year production period (2026–2060). This study focuses on a reservoir containing bitumen with an initial viscosity between 10,000 an‎d 21,000 centipoise at a normal temperature of 25.0 °C. Six different operational an‎d structural scenarios are eva‎luated to determine the optimal strategy for maximizing recovery while maintaining vapor chamber stability. Simulation results show that natural depletion (Case 1) is entirely inefficient for such reservoirs, yielding negligible recovery factors. In contrast, propane injection significantly reduced bitumen viscosity, lowering it from over 20,000 centipoise to below 100 centipoise within the mixing zone, a reduction of over 99%. Sensitivity analysis revealed that injection pressure is the primary factor influencing recovery kinetics. While injection at a constant high pressure of 1500 kPa (Case 3) provided the fastest initial filling, it resulted in a narrower vapor chamber. The research identifies a rapid evaporation mechanism where a dro‎p in reservoir pressure below propane vapor pressure approximately 900 kPa leads to rapid gas expansion, which is essential for side chamber growth an‎d increased displacement efficiency. Advanced strategies, including a gradual pressure reduction strategy (Case 4) an‎d a periodic pre-saoking strategy (Case 5), were found to be superior. Case 5, which involved simultaneously stimulating both the injection an‎d production wells for an initial three years, effectively eliminated bottleneck near the well, resulting in the highest observed peak production rate of approximately 100 m³/day. Furthermore, the introduction of a cross-well design with horizontal displacement (Case 6) demonstrated a significant improvement in volumetric sweeping efficiency by creating diagonal drainage paths that reach the stagnant bitumen at the reservoir boundary. This study concludes that for shallow reservoirs of 91 meters in depth, a hybrid approach combining high-pressure initial stimulation with subsequent pressure reduction an‎d interlocking well engineering provides the most technically robust framework for commercial bitumen extraction. These findings offer a roadmap for improving non-thermal enhanced oil recovery (EOR) in shallow, high-viscosity environments where energy efficiency an‎d environmental impact are critical considerations.

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حميدرضا شاه وردي , محسن محمدي