PETRONAS encounters an imperative strategy in rising gas demand which requires the development of gas fields with high CO2 content. However, this strategy poses a significant challenge, given that the ensuing CO2 emissions are anticipated to surpass the designated reduction limits crucial for attaining net zero carbon emissions by 2050. To uphold sustainable development, the emphasis now turns to the pivotal necessity of decarbonisation through the sequestration of CO2, whether within depleted gas reservoirs or saline aquifers.
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 characterised by an initial CO2 content of ~60 per cent. Through a comprehensive analysis encompassing key field parameters, the study aims to optimise cumulative gas production while effectively managing CO2 storage. A robust compositional dynamic model is constructed, incorporating specialised CO2 storage features. 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 optimisation.
The principal objective of this investigation is to assess the viability of simultaneous gas production and CO2 injection within the same geological formation during the field's developmental stages. The study's findings obtain a baseline scenario yielding an ultimate recovery factor of approximately 73 per cent from an initial gas in-place of ~3.40 TSCF, in the absence of CO2 injection. Notably, the focus on sequestration modelling introduces critical constraints related to CO2 mole fraction in the production well stream and the separation efficiency of surface facilities. Against this backdrop, the feasibility of recycling produced CO2 emerges as a technologically and economically viable option for gas field development. By optimising the integration of net hydrocarbon production and CO2 storage capacity, a scenario is identified that achieves 100 per cent CO2 separation efficiency and an 80 per cent mole fraction cutoff. This optimised approach results in a net effective storage capacity of 1.3 TSCF and a gas reserve potential of 2.1 TSCF, representing a reduction of approximately 14 per cent compared to the baseline scenario. Additionally, net hydrocarbon production is estimated at 0.9 TSCF, underscoring the impact of in-situ CO2 injection on overall production.
This study introduces an innovative development that aligns high CO2 gas field production with ambitious net zero carbon emission targets. By seamlessly integrating CO2 sequestration, the approach not only mitigates emissions but also prevents the need for transporting CO2 to flaring streams. Furthermore, the study proposes for a well-coordinated Field and Storage Development Plan (FSDP), which enhances the asset values through snergistic developments by unlocking of additional gas reserves and supported by CO2 management practices.
