A Multi-scale Approach for CO2 Accounting and Risk Analysis in CO2 Enhanced Oil Recovery Sites

Abstract:

Using carbon dioxide in enhanced oil recovery (CO₂-EOR) is a promising technology for emissions management because CO₂-EOR can dramatically reduce carbon sequestration costs in the absence of greenhouse gas emissions policies that include incentives for carbon capture and storage. This study develops a multi-scale approach to perform CO₂ accounting and risk analysis for understanding CO₂ storage potential within an EOR environment at the Farnsworth Unit of the Anadarko Basin in northern Texas. A set of geostatistical-based Monte Carlo simulations of CO₂-oil-water flow and transport in the Marrow formation are conducted for global sensitivity and statistical analysis of the major risk metrics: CO₂ injection rate, CO₂ first breakthrough time, CO₂ production rate, cumulative net CO₂ storage, cumulative oil and CH₄ production, and water injection and production rates. A global sensitivity analysis indicates that reservoir permeability, porosity, and thickness are the major intrinsic reservoir parameters that control net CO₂ injection/storage and oil/CH₄ recovery rates. The well spacing (the distance between the injection and production wells) and the sequence of alternating CO₂ and water injection are the major operational parameters for designing an effective five-spot CO₂-EOR pattern. The response surface analysis shows that net CO₂ injection rate increases with the increasing reservoir thickness, permeability, and porosity. The oil/CH₄ production rates are positively correlated to reservoir permeability, porosity and thickness, but negatively correlated to the initial water saturation. The mean and confidence intervals are estimated for quantifying the uncertainty ranges of the risk metrics. The results from this study provide useful insights for understanding the CO₂ storage potential and the corresponding risks of commercial-scale CO₂-EOR fields.