Doctor of Philosophy (PhD)
The Gas-Assisted Gravity Drainage (GAGD) process was developed as an alternative to conventional gas injection enhanced oil recovery (EOR) processes, which suffer from their inherent weakness of combating gravity segregation. The GAGD process, however, is aimed at taking advantage of this phenomenon and consists of using horizontal producers near the bottom of the payzone while injecting gas using vertical injection wells. It is hypothesized that the injected gas will rise to the top, thereby forming a gas cap while displacing reservoir brine/oil downward towards the producers. In this study, a single-well alternative to the multi-well GAGD process was investigated to determine the operating constraints that would result in maximum oil recovery, and the main areas of improvement/adaptation for implementation in the Buckhorn Field, an onshore Louisiana reservoir. In the newly proposed process, the gas injection and fluid production occur along the same wellbore; however, they would be located in different sections with the production completions in either a horizontal section of the well or in a lower-lying section of a vertical well. The study was comprised of reservoir condition coreflooding experiments to elucidate the pertinent data to the field application of this single-well GAGD process. This data was then used in field-scale numerical simulations to optimize the proposed process with regards to maximum oil recovery by investigating various well locations/configurations, and production strategies. In order to frame the proposed processes’ technical feasibility they were compared to other commonly implemented EOR processes, such as Continuous Gas Injection and Water-Alternating-Gas. Finally, an economic assessment of all of the investigated gas EOR processes was carried out to quantify the risk associated with their application. For this purpose, a cashflow analysis was conducted using Excel after which Crystal Ball was utilized to generate the confidence intervals for selected economic performance indicators. The numerical simulation study revealed that the multi-well GAGD process resulted in the highest oil recovery (50–58 %ROIP or 2.0–2.6 million STBO) while the economic study showed that all GAGD process variations would be profitable. However, the vertical single-well GAGD process ranked the highest based on the Internal Rate of Return and the Profitability Index.
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Paidin, Wagirin Ruiz, "Evaluation of Gas-Assisted Gravity Drainage EOR Process Applicability in a Louisiana Oil Field through Experiments and Reservoir Simulation" (2013). LSU Doctoral Dissertations. 2035.