Practical Leakage Risk Assessment for CO2 Assisted Enhanced Oil Recovery and Geologic Storage in Ohio's Depleted Oil Fields

Abstract

A method for estimating the expected liability (risk) associated with wellbore leakage during and after geologic storage operations is presented using three of Ohio’s oil fields as case studies. The risk framework described in this study uses the bowtie method with features, events, and processes (FEPs) descriptors to identify and assess risk posed by legacy wells. The bow-tie framework allows simple visualization of top risk events (hazards). The probability of triggering the hazard is quantified based on estimation of the wellbore’s integrity while the consequences are modeled based on low- and high-cost outcome scenarios. This method builds upon previous work. It estimates current wellbore integrity using characteristic categories to develop a proxy for leakage likelihood. Proxy categories were: Spud Date, Treatment, Well Status, Plugging and Abandonment (P&A) Date, Well Type, Plug, Surface Cement, and Primary Cement. Separate risks were developed for each well and each scenario. The consequence of a leakage event was estimated based on costs to businesses and property owners for each leakage scenario. Using the likelihood of leakage calculated for each field and the cost of potential consequences, the risks for each field were estimated to be between $10 million to $63 million for the three fields of interest. Overall, the identification of threats, hazards, and consequences and the identification of barriers to lessen the likelihood of occurrence or minimize consequences aids in the development of a targeted CCUS strategies.