Model-based cost analysis for pressure and geochemical-based monitoring methods in CO2-EOR fields: application to field A

Decision making using monitoring data from CO2 geological storage (GS) projects can be multifaceted and complex because of geological, environmental, political, and economic factors. This study primarily focuses on economic and technical aspects of monitoring projects for CO2. The focus of this research is to compare the economic effectiveness of pressure-based monitoring (PBM) and geochemical-based monitoring (GBM) on CO2 leakage detection in CO2-EOR sites where risk for leakage assumed to be plugged and abandoned (P&A) wells, however methodology can be easily applied to CO2 storage in saline aquifers as well. PBM can detect leakage from pressure anomalies, while GBM method detects leakage from alteration in fluid chemistry. In this paper, analytical and semi-analytical models for PBM and GBM techniques were applied to calculate the number of monitoring wells required for monitoring anomalies, which could be due to leakage of CO2. In this study, we assumed that leakage through P&A wells represents the main risk factor. The goals of this study are to determine the cost effectiveness of PBM and GBM as a means to maximize the spatial coverage of the monitoring network in the vicinity of P&A wells. We used different analytical models for PBM and GBM, and overlaid the spatial coverage of each well onto a typical Texas Gulf Coast field site (known as Field A), thus identifying the intersection of each monitoring well and potentially leaking P&A well. Then, based on the available cost data, the costs of each PBM and GBM well were estimated and the two monitoring techniques were compared economically, assuming a pre-determined budget is available to invest on monitoring. The results showed that the spatial coverage of each PBM well was much higher than each GBM wells, and that the total capital and operational cost per PBM well was lower than each GBM well. For theoretical site used in this work, only 29 PBM wells were needed for full coverage of the field site, while 169 GBM wells were required. Therefore, we concluded that PBM technique is a more cost effective option, considering the parameters and assumption in this case study.