Post-SAGD Efficiency Improvement
Creators: Pratama, Randy Agra
Publisher: name: University of Alberta Library
Year: 2024

<p>Steam-assisted gravity drainage (SAGD) has proved to be a technically and commercially successful methodology for recovering heavy-oil in Canada. At present, there are 22 commercial SAGD projects with over 300 pads and 2,700 well pairs, contributing to over 1.5 million bbl/day of production. The steam growth in the steam chamber could recover up to 60% of the oil-in-place by a typical SAGD project. However, some SAGD projects are only able to present less than 20% of the recovery factor, even though they have been producing for almost decades. Currently, the steam-to-oil ratio (SOR) for most SAGD projects ranges between 2 and 4 bbl steam/bbl oil. Nevertheless, some projects are still experiencing SOR of over 4 bbl/bbl due to the aggressive steam injection. Despite the efficacious evidence and enormous contribution to oil production, many questions regarding the current SAGD project performance are still rising.  The process and execution are very complex and entail great operational excellence. The thermodynamic processes (heat transfer, wettability alteration), reservoir geology (thickness, vertical conformance, steam channeling), well designs (optimal placement of the pairs, well completions), and environmental concerns (GHG emission) are also limiting factors to be detrimental to SAGD performance. Some other techniques to recuperate heavy-oil and bitumen (e.g., co-injection)—in addition to the principal SAGD—have been insinuated and employed in the projects. The efforts only presented a 5–10% success rate. The steam generation process itself may lead to environmental issues and low economic viability. Many worldwide steam projects, including SAGD projects in Canada, have already reached their maturity with a severe decline in production despite continuous steam injection. Escalating greenhouse gas (GHG) emissions is another crucial downside of steam injection application, contributing to an emission growth rate of about 1.9% worldwide and 0.8% annually in Canada. This requires us to search for different techniques to deplete the remaining (conditioned) oil efficiently and in an eco-friendly manner. This research focuses on the testing of a new technique to minimize GHG emissions resulting from steam generation while enhancing the ultimate recovery for post-SAGD efficiency improvement.</p>

<p>In obtaining a comprehensive understanding of post-SAGD efficiency improvement process, a new generation steam additive (e.g., switchable-hydrophilicity tertiary amines or SHTA) and a range of condensable and non-condensable solvents as single and multiple components (e.g., methane, propane, heptane), and non-hydrocarbon solvents (e.g., CO2 gas) were included as potential solvents. We perceived that favorable interfacial tension reduction was achieved, and irreversible wettability could be auspiciously restored after combining SHTA with steam because of the solid-phase surface charge modification to be more negatively charged. Phase distribution or residual oil in the porous media developed after steam injection was able to be auspiciously convalesced, indicating that capillary forces could be reduced. Consequently, over 80% of the residual oil could be recuperated post-SHTA injection presenting favorable oil recovery performance. In addition to this promising evidence, SHTA could be potentially recovered by switching its reversible chemical reaction to be in hydrophobic form; hence, promoting this steam additive to be both reusable and more economically effective. Based on the outputs obtained from different experimental methodologies, the underlying recovery mechanisms induced by the potential steam additives were identified. The results revealed that synergy among the recovery mechanisms presented by steam additives could potentially improve the heavy-oil/bitumen recovery post-SAGD. Furthermore, it was also observed that both hydrocarbon (condensable and non-condensable) and non-hydrocarbon solvents could substantially improve incremental heavy-oil/bitumen recovery by up to 50%. More essentially, aggressive steam utilization could be terminated entirely, and energy efficiency could be significantly improved by nearly 100% by applying this technique. </p>

<p>A comprehensive analysis of the mechanics of the heavy-oil/bitumen recovery (e.g., interfacial properties, phase distribution in porous media, recovery performance) provides valuable substantiation and understanding, honoring the potential implications of utilizing steam additives as potential steam additives to the post-SAGD recovery process. Moreover, hydrocarbon and non-hydrocarbon solvents with different compositions were introduced as potential solvents to recuperate heavy-oil and bitumen recovery and reduce or even completely cut off the steam injection at late-stage SAGD, diminishing its GHG emission and improving energy efficiency. Valuable findings present beneficial recommendations for low-emission and high-efficiency late-stage heavy-oil recovery as post-SAGD applications, as well as other types of steam injection processes.</p>