Simulation of CO2 Injection in a Reservoir with an Underlying Paleo Residual Oil Zone
MetadataShow full item record
Paleo residual oil zones (PROZs) are zones below the oil-water contact (OWC) thatcontain residual oil. These types of zones exist in many fields around the world, but isoften given little attention, due to traditionally being considered unproducible. Amodern enhanced oil recovery (EOR) technique that has showed promising results inPROZs is CO2 injection. Still, companies typically are reluctant to commence CO2 EORprojects because of the large upfront costs and uncertainty related to how the projectwill develop. Unforeseen heterogeneities may for example reduce the degree of mixingof CO2 and oil, even under miscible conditions. It may also lead to unexpectedresidual oil saturation after injection of CO2, in parts of the reservoir. Thus, it isimportant to evaluate effect of CO2 injection start and CO2 injection rate. Thoseparameters influence necessary infrastructure capacity and design. Evaluation ofTodd-Longstaff mixing parameter and residual oil saturation to miscible CO2 injectionis also of interest. These are two uncertain parameters that may be dependent onheterogeneities within the reservoir.In this thesis, sensitivity analysis of CO2 injection start, CO2 injection rate,Todd-Longstaff mixing parameter, and residual oil saturation after injection of CO2 ispresented. General trends were noticed; 1. more oil was produced sooner withincreased CO2 injection rate. 2. It seemed beneficial to start CO2 injection immediatelyafter oil production rate, during waterflooding, had stabilized at a low value. 3.Todd-Longstaff mixing parameter and residual oil saturation after CO2 injectionimpacts effectiveness of CO2 EOR significantly. Substantial amounts of oil wasproduced from the PROZ and main pay zone (MPZ) in many of the cases ran, whenCO2 was injected, compared to when water was injected throughout. However, most ofthe extra oil produced came from the MPZ. That will often be the case in field projectsas well, and typically it is essential that the MPZ can benefit from CO2 injection, if CO2EOR projects are to be commenced in the PROZ. Furthermore, qualitative commentswere provided about economics regarding results of the sensitivity analysis.