Abstract
With only less than 10% recovery, the primary production of hydrocarbon from shale reservoirs has redefined the energy equation in the world. Similar to conventional reservoirs, Enhanced Oil Recovery (EOR) techniques could be devised to enhance the current recovery factors. However, shale reservoirs possess unique characteristics that significantly affect the fluid properties. Therefore, we are adopting a molecular simulation approach that is well-suited to account for these effects to evaluate the performance of three different gases, methane, carbon dioxide and nitrogen, to recover the hydrocarbons from rough pore surfaces. Our hydrocarbon systems consists of either a single component (decane) or more than one component (decane and pentane). We simulated cases where concurrent and countercurrent displacement is studied. For concurrent displacement (injected fluids displace hydrocarbons towards the production region), we found that nitrogen and methane yielded similar recovery; however nitrogen exhibited a faster breakthrough. On the other hand, carbon dioxide was more effective in extracting the hydrocarbons when sufficient pressure was maintained. For countercurrent displacement (gases are injected and hydrocarbons are produced from the same direction), methane was found to be more effective, followed by carbon dioxide and nitrogen. In all cases, confinement reduced the recovery factor of all gases. This work provides insights to devise strategies to improve the current recovery factors observed in shale reservoirs.
Highlights
While abundant, shale formations are unique and serve as unconventional hosts for hydrocarbons [1]
The current recovery factors are less than 10%, even with the most efficient completion schemes [6,7]
Enhanced oil recovery techniques have been widely-used in conventional reservoirs [8,9]
Summary
Shale formations are unique and serve as unconventional hosts for hydrocarbons [1]. Hoffman [24] studied the feasibility of various gases for injection in Bakken and reported better performance for the miscible cases. They encouraged the implementation of EOR since significant oil could be recovered regardless of the gas type. Liu et al [35] designed a case study to evaluate the potential of CO2 -EOR in the Bakken formation where promising results were observed. Kerr et al [37] developed an Eagle Ford case study to engineer single- and multi-well CO2-EOR techniques and reasonable agreement with the field results was reported.
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