Real-Time Evaluation of Carbon Dioxide Production and Sequestration in a Gas Field

Abstract

Summary The production of a substantial fraction of carbon dioxide (CO2) in any hydrocarbon-gas stream poses a significant challenge in terms of separation and sequestration. Both environmental concerns and economic incentives encourage the operators to search for safe, cost-effective ways of disposing of CO2. This paper presents a case study in which a pragmatic solution of CO2 separation at surface and its disposal in a saline aquifer occur in close proximity to its source. A suite of both modern and classical analytical tools is used to understand the production behavior of individual wells. This understanding is imperative because production volume is dictated by the ability to dispose of the associated CO2 volumes to honor the fault-activation pressure limit. The analytical tool kit—transient-productivity index (PI), combined static and dynamic material-balance (MB) methods, and rate-transient analysis (RTA), among others—allowed for the rapid assessment of both the producing gas reservoir and the saline aquifer receiving the CO2 stream. The use of real-time data allowed a comprehensive assessment of in-place volumes for the source gas and the capacity of the aquifer. The injection of supercritical CO2 suggests that the terminal aquifer pressure has been reached by encountering less-than-expected storage volume and by the lowering of fracture-pressure gradient. On-time learning has allowed the asset team to search for alternative CO2-disposal solutions to ensure continuous gas production from this field.