(756c) Plugged Well Leakage Risk Assessment in a Carbon Sequestration Project

Abstract

Carbon sequestration has been proposed as a promising way to mitigate the accumulation of greenhouse gases. Depleted oil and gas reservoirs can be considered as desirable vessel for carbon sequestration. It is crucial to maintain the integrity of formations that contain high concentration of CO₂. Plugged wells can be one of the risky leakage pathways which defect the purpose of carbon sequestration. The leak risk of plugged wells should be monitored and evaluated through the whole lifetimes of carbon sequestration activities.

Even though numerous researches focused on the well integrity assessment for carbon sequestration projects, a systematic manner addressed the plugged wells’ CO₂ leakage in a practical way has not been presented. This study will fill this gap. Lean analysis was performed by using Cause and Effect Analysis (CEA) method and Failure Mode and Effects Analysis (FMEA) method. CEA was used to identify all the possible causes that could result to the CO₂ leakage of plugged wells, while FEMA was implemented to build the plugged well failure modes and evaluate the possibility of CO₂ leakage for plugged wells.  WH field, a CO₂ EOR oil field located in the Gulf of Mexico, was studied as an example to explain how CEA and FMEA could be functioned as effective methodologies to evaluate the CO₂ leak potentials of the plugged wells. The plugged wells with high risk of leakage were predicted. Lean analysis were proven to be an effective way to evaluate the risk of CO₂ leakage for plugged wells in carbon sequestration activities. The proposed method can also be used in evaluating the integrity of CO₂ injection wells and oil production wells in an oil field where CO₂ is or will be injected in the future.