Integrated Approach to Gasfield Development, Carbon Sequestration Minimizes Emissions

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 221264, “Maximizing Value and Minimizing Emissions Integrated Approach to Gasfield Development and CO2 Sequestration: A Pathway to Net-Zero Emissions, ” by Ahmad Khanifar, SPE, Petronas, and Seyed Mousa Mousavimirkalaei, Computer Modelling Group. The paper has not been peer reviewed. _ This study explores the feasibility of implementing in-situ CO2 recycling for sequestration as a fit-for-purpose developmental strategy for a Malaysian gas field characterized by an initial CO2 content of approximately 60%. Through a comprehensive analysis encompassing key field parameters, the study aims to optimize cumulative gas production while effectively managing CO2 storage. A robust compositional dynamic model is constructed. The model facilitates the recycling of produced CO2 between gas producers and CO2 injectors, while the introduction of CO2 tracers for each well enables the differentiation of CO2 sources, enhancing shutdown strategies and parameter optimization. Field Overview and Field and Storage Development Plan (FSDP) Concept The focus of this feasibility study is an offshore gas field in a predevelopment stage. The geological interpretation suggests a predominantly shoreface depositional environment. Exploration and appraisal drilling within the field have predominantly encountered gas reserves with minor oil occurrences, notable for their high CO2 content. Despite the absence of production history, the field exhibits substantial hydrocarbon potential across multiple reservoirs, with indications of oil-rim prospects and overpressure zones in deeper formations. The pervasive challenge in field development stems from the substantial CO2 content, reaching up to 70%. This paper examines the feasibility of repurposing produced CO2 for sequestration within one of the main reservoirs of the field, herein referred to as the targeted reservoir, exhibiting an initial CO2 content of approximately 60%. The primary aim of this study is to assess the viability of concurrent gas production and CO2 injection within the same geological formation during field development. The investigation encompasses an in-depth analysis of the repercussions of CO2 sequestration within the field on crucial parameters, including hydrocarbon reserves, recovery efficiency, production dynamics, CO2 breakthrough timing, gas quality, and project economics. Fundamental to this endeavor is the optimization of cumulative gas production and effective CO2 storage volume, serving as pivotal metrics for project success. The FSDP concept represents a cohesive combination of the field development plan and the storage development plan adapted specifically for the targeted reservoir. In essence, the FSDP gas with high CO2 content at the surface, followed by the separation and removal of CO2 by surface-facility separation units. Subsequently, the separated CO2 is recycled and injected back into the reservoir through dedicated injectors positioned below the water/gas contact. The quantity of recycled CO2 and the quality of sales gas within the production stream are contingent upon the efficiency of the separation process and applied technologies, which are subject to optimization analyses. Practically, the efficacy of the separation unit dictates the quality of the sales gas, a critical consideration in the development plan of gas fields laden with impurities such as CO2. The complete paper discusses two distinct separation unit efficiencies: 100% and 80%, alongside the corresponding quality of the gas outlet.