Loading...
Cost-effective chemical EOR in conventional carbonate reservoirs: simple ketones and surfactants
Alghunaim, Etaf
Alghunaim, Etaf
Citations
Altmetric:
Advisor
Editor
Date
Date Issued
2021
Date Submitted
Keywords
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
Abstract
This thesis presents an evaluation of the effectiveness of a simple chemical Enhanced Oil Recovery (EOR) method consisting of a low cost, low molecular weight ketone and a non-ionic surfactant for use in waterflooding as an alternative to conventional chemical EOR in heterogeneous carbonate reservoirs. We believe adding these simple chemical additives to the injection brine should improve oil displacement efficiently significantly—especially in heterogeneous carbonate reservoirs. The evaluation includes static experiments using high-salinity brine, low-salinity brine, low-salinity brine plus a ketone, and low-salinity brine and a non-ionic surfactant—all surrounding a carbonate core in an imbibition cell. The mass transfer environment mimics a fracture-matrix interface in fractured carbonate reservoirs, and the driving forces in such experiments are spontaneous imbibition, osmosis, and wettability alteration when ketone is used.
Four different EOR experiments utilizing spontaneous imbibition by capillary action, chemical osmosis, and miscible mixing leading to slight wettability alteration and viscosity reduction, all in absence of any forced displacement, were conducted on several 1-1/2-inch diameter by 1-1/2-inch San Andres carbonate cores in following order: 1) Low-salinity brine EOR only, 2) Low-salinity brine EOR with an added non-ionic surfactant, 3) Low-salinity brine EOR with a ketone, and 4) Low-salinity brine EOR with a non-ionic surfactant and a ketone. The permeability and porosity of the tested cores ranged between 2 to 20 md and 7 to 16%, respectively. As mentioned earlier, the oil recoveries resulted from spontaneous imbibition invoked by different displacement mechanisms. No forced displacement was included in the experiments for two reasons: 1) To mimic fracture-matrix passive oil recovery across fracture-matrix interface. 2) To have a similar and comparable approach for all four EOR experiments and associated processes. Solution density and pH were continuously recorded during the experiments to determine the oil recovery mechanism of each experiment. An increase in the solution pH could lead to wettability alteration as a component of EOR mechanism; however, there is reliable evidence that ketones alter wettability of cores to water-wet conditions. Experiments reported by Wang, Abeykoon, et al. (2019) clearly indicate that ketones alter carbonate wettability to strong water-wet—consistent with our experimental results. However, our low-salinity vs. high-salinity experiments indicate that low-salinity enters the core by osmosis.
The results show that low-salinity brine with added ketone yielded the highest overall oil recovery of 44%, compared to 11% by low-salinity brine plus surfactant and 11.14% by low-salinity brine alone. Finally, the combined use of brine-surfactant-ketone enhanced the oil production by 23%.
Associated Publications
Rights
Copyright of the original work is retained by the author.