Measurement and analysis of oil-gas diffusion at reservoir conditions: application to huff-n-puff EOR in unconventional reservoirs

Mukherjee, Sanchay

Measurement and analysis of oil-gas diffusion at reservoir conditions: application to huff-n-puff EOR in unconventional reservoirs

dc.contributor.advisor	Rai, Chandra
dc.contributor.author	Mukherjee, Sanchay
dc.contributor.committeeMember	Devegowda, Deepak
dc.contributor.committeeMember	Sondergeld, Carl
dc.date.accessioned	2020-12-10T18:26:34Z
dc.date.available	2020-12-10T18:26:34Z
dc.date.issued	2020
dc.date.manuscript	2020
dc.description.abstract	Due to the extremely low permeability and high depletion rate, primary recovery from unconventional reservoirs is generally low. Huff-n-Puff has proved to be a successful EOR technique in tight formations, such as the Eagle Ford. However, the underlying transport mechanism remains poorly understood. Recent studies show oil-gas diffusion is a key factor in huff-n-puff EOR. Due to concentration gradients, injected gas molecules diffuse into in-situ oil causing it to swell and consequently to be expelled out of the nanopores into the micro- and macro- fractures. We have designed an experiment with a high-pressure, high-temperature cell having observation windows for the measurement of oil swelling and diffusivity. The measurements have been done on Wolfcamp A oil (API-32), Meramec oil (API-43) and Eagle Ford oil (API-53) with 3 different gas mixtures of methane – ethane, at a temperature of 175°F to evaluate the impact of injection pressure (above and below Minimum Miscibility Pressure-MMP), injectate gas composition, API gravity and viscosity of oil on oil-gas diffusivity. The results show that the diffusivity of injectate gas into the oil phase as a function of pressure and increases to maximum at MMP, beyond which it decreases. Enrichment of the injection gas increases the oil-gas diffusivity at the same pressure. Regardless of injection pressure, for the gas mixture C1/C2 (72/28 mole%) the diffusion coefficient varies between 10-11 m2/s to 10-10 m2/s for Wolfcamp A oil; 10-10 m2/s to 10-9 m2/s for Meramec oil and 10-9 m2/s to 10-8 m2/s for Eagle Ford oil. Tight reservoirs generally have a high matrix tortuosity, which impacts the diffusion efficiency in the porous media. Using tortuosity values available in the literature and diffusivities of oil gas systems measured in this study, we estimate that the injected gas can only travel 0.2-0.9 ft away from the fracture-faces during 6 months of gas injection. Low tortuosity and high diffusion rates favor economic recoveries. This study highlights the importance of stimulated reservoir area (SRA) characterization, nanoporous tortuosity and diffusivity measurements in optimizing huff-n-puff recovery in shales.	en_US
dc.identifier.uri	https://hdl.handle.net/11244/326601
dc.language	en_US	en_US
dc.subject	Engineering, Petroleum.	en_US
dc.subject	Unconventional Reservoirs	en_US
dc.subject	EOR	en_US
dc.subject	Diffusion	en_US
dc.thesis.degree	Master of Science	en_US
dc.title	Measurement and analysis of oil-gas diffusion at reservoir conditions: application to huff-n-puff EOR in unconventional reservoirs	en_US
ou.group	Mewbourne College of Earth and Energy::Mewbourne School of Petroleum and Geological Engineering	en_US