Abstract
Steam-assisted gravity drainage (SAGD) is a mature technology for bitumen recovery from oil sands. However, it is an energy-intensive process that requires large amounts of steam to heat and mobilize bitumen. The purpose of this work is to develop ways to enhance SAGD performance through the use of organic base additives. The research is approached from three focus areas that supplement and guide each other: characterization tests, sand-pack floods, and computational simulation. A number of key mechanisms for enhancing oil recovery were identified, high-temperature additive characterization tests were developed, and promising alkalis were tested in porous media. Simulation was employed to history-match sand-pack flood production data, in order to demonstrate the effect of an additive on the oil–water relative permeability. Based on these results, it was concluded that oxygenated organic bases had the most potential for improving bitumen recovery through reducing the oil–water interfacial tension (IFT) by increasing the pH of the system. These organic bases favorably modify the interfacial energies between the immiscible oil–water phases and enable them to flow easily through the porous media during production. Sand-pack flood tests have successfully demonstrated a 10%–15% improvement in bitumen recovery, over baseline, in the presence of IFT-reducing additives. Simulation results further showed that an IFT reduction had a positive impact on SAGD performance. This work demonstrates the potential of organic bases to improve not only SAGD, but other steam injection processes. Furthermore, a number of experimental methods were developed, tried, and tested during the course of this work.
Highlights
At typical oil sands reservoir temperatures (4–38 °C), bitumen is highly viscous and practically immobile (Dusseault 2001)
In steamassisted gravity drainage (SAGD), steam is injected at high temperature and pressure underground into the oil sands reservoir through sets of horizontal wells (Butler 1994)
It can be inferred that the bases should be quite effective at forming in situ surfactants at high temperatures, which can lower interfacial tension (IFT)
Summary
At typical oil sands reservoir temperatures (4–38 °C), bitumen is highly viscous and practically immobile (Dusseault 2001). Steam is typically used due to its price, availability, and high heat capacity. In steamassisted gravity drainage (SAGD), steam is injected at high temperature and pressure underground into the oil sands reservoir through sets of horizontal wells (Butler 1994). The injected steam propagates in the formation and forms a steam chamber along the horizontal length. At the edge of the steam chamber, steam condenses, liberating its heat, and causes a reduction in the bitumen viscosity, which allows the oil to gravity-drain along with condensed water into production wells. The production wells are sets of horizontal wells located below the steam injection wells.
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