(772d) Assignment and Calibration of Relative Permeability By Hydrostratigraphic Units: A Novel Approach for Multiphase Flow Analyses; Case Study Example: CO2-EOR Operations at the Farnsworth Unit, Texas

Among the most critical factors for geological CO₂ storage site screening, selection and operation is effective simulation of multiphase flow and transport. Relative permeability is probably the greatest source of potential uncertainty in multiphase flow simulation, second only to intrinsic permeability heterogeneity. The specific relative permeability relationship assigned greatly impacts forecasts of CO₂ trapping mechanisms, phase behavior, and long-term plume movement. A primary goal of this study is to evaluate the impacts and implications on CO₂-EOR model forecasts of different methods of assigning relative permeability relationships.

We applied a novel approach to assigning relative permeability relationships in numerical models. In previous research, most models assign relative permeability functions on the basis of geologic formation or rock type. In this study, we assign and calibrate relative permeability by hydrostratigraphic units, extending the seminal work of Maxey (1964) to multiphase flow. Ongoing work by the SWP has identified distinct regions that are believed to exhibit similar flow characteristics using the Improved Hydraulic Flow Units (IHFU) method. Core from each of these flow regions are being scanned by micro-computer-tomography (micro-CT) and relative permeability testing will be completed when the scans are finished. Specific, calibrated relative permeability relationships will be assigned to each hydrostratigraphic unit. Results of forward simulations with the newly-calibrated models will be compared to those of existing models that utilize a single relative permeability relationship for the whole model domain.

The study site is the Farnsworth Unit (FWU) in the northeast Texas Panhandle, an active CO₂-EOR operation. The target formation is the Morrow ‘B’ Sandstone, a clastic formation composed of medium to course sands. The study was undertaken as part of the Southwest Regional Partnership on Carbon Sequestration (SWP) under the phase III project.