North-Central Section - 50th Annual Meeting - 2016

Paper No. 22-9
Presentation Time: 10:55 AM


GERSHENZON, Naum I.1, RITZI Jr., Robert W.1, DOMINIC, David F.1, OKWEN, Roland T.2, MEHNERT, Edward2 and PATTERSON, Christopher2, (1)Earth and Environmental Sciences, Wright State University, 3640 Colonel Glenn Hwy, Dayton, OH 45435, (2)Illinois State Geological Survey - Prairie Research Institute, University of Illinois at Urbana-Champaign, 615 E. Peabody Dr, Champaign, IL 61820,

A number of important candidate CO2 reservoirs exhibit sedimentary architecture reflecting fluvial deposition. Recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to CO2 injection and storage. We used a geocellular modelling approach to represent this multi-scaled and hierarchical sedimentary architecture. With this model, we investigated the dynamics of CO2 plumes, during and after injection, in such reservoirs.

Capillary trapping and dissolution are primary short term processes for CO2 immobilization in deep brine reservoirs. There are two main residual capillary trapping mechanisms: 1) CO2 bubbles are trapped within pore spaces because of “snap off”, a process in which counter-imbibition of brine behind the advancing plume traps residual CO2 bubbles within the intervening pore bodies; 2) trapping due to heterogeneity in the capillary entry pressure among reservoir rock types, i.e. CO2 is pinned below local contacts between an underlying reservoir rock type with larger pores and an overlying reservoir rock type with smaller pores and thus larger entry pressure. It will be shown that the later mechanism may dominate in fluvial type reservoirs which include small-scale (cm to meter) heterogeneity in permeability and capillary pressure.

CO2 trapping and dissolution are profoundly impacted by the type of capillary pressure curve used, i.e. Brooks-Corey or van Genuchten . This difference is especially pronounced in heterogeneous reservoirs. It will be demonstrated that CO2 plume shape and position (simulated with Brooks-Corey or van Genuchten curves) may be significantly different a long time after CO2 injection ceases.

The detailed petrophysical and geological parameters of any specific reservoir are typically uncertain, which motivates studies of parameter sensitivity. Sensitivity analysis on the variability of basic parameters, such as contrast in permeability, irreducible water saturation, trapping saturation, and capillary entry pressure, will be presented.