CO2-Based Enhanced Oil Recovery From Unconventional Reservoirs

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 168979, “CO2-Based Enhanced Oil Recovery From Unconventional Reservoirs: A Case Study From the Bakken Formation,” by G. Liu, J.A. Sorensen, J.R. Braunberger, R. Klenner, J. Ge, C.D. Gorecki, E.N. Steadman, and J.A. Harju, University of North Dakota, prepared for the 2014 SPE Unconventional Resources Conference—USA, The Woodlands, Texas, USA, 1–3 April. The paper has not been peer reviewed. In this study, detailed petrophysical and geological field models focusing on the middle and lower members of the Bakken Formation were developed on the basis of field characterization, well-log interpretation, and laboratory core analysis by scanning-electron-microscopy, ultraviolet-fluorescence, and standard-optical-microscopy techniques. A fine-scale model with a pair of horizontal wells was extracted from the initial model (Bailey area) to examine the potential effectiveness of oil-recovery techniques based on carbon dioxide (CO2) injection. The results show that CO2 injection may play a significant role in increasing oil production. Introduction Small improvements in productivity could increase technically recoverable oil in the Bakken by billions of barrels. While the use of CO2 in conventional reservoirs is a widely applied and well-understood practice, its use for enhanced oil recovery (EOR) in tight oil reservoirs is a relatively new concept. The use of CO2 as an injection fluid may reduce the hydrocarbon viscosities in the reservoir and allow additional trapped oil to be produced. Another benefit of CO2 injection is to mitigate climate change by storing CO2 in the reservoir. The Energy & Environmental Research Center has conducted a multidisciplinary research program with the ultimate goal of providing industry with insight regarding the potential to use CO2 for EOR in the Bakken and Three Forks Formations. The Bakken CO2 Enhanced Recovery and Storage Project began in 2012 and was completed in 2013. The objective of this project was to use reservoir characterization and laboratory analytical data (e.g., core analyses, well logs, and oil analyses) coupled with state-of-the-art modeling to examine the viability of using CO2 for simultaneous CO2 storage and EOR in the Bakken. The ultimate goal of the project was to have a Bakken operator apply the knowledge gained from the laboratory, characterization, and modeling activities to a pilot-scale field test of CO2 injection into a Bakken or Three Forks reservoir. The presentation in this paper comprises a discussion of the initial near-wellbore-modeling aspect of the project.