CO2 Storage Potential Evaluation of Restricted Saline Aquifers in Peninsular Malaysia Offshore
Authors: Das Debasis P , Tiwari Pankaj K , Rahman M Zahari B A , Mohamad M Naim B , Chidambaram Prasanna , Razali Nur Myra Rahayu , Yakup M Hamzi B , Majidaie Saeed , Wah Tan Seng , Mat M Noor Fajarimi B C , Amir M Syafeeq B E , Fadhlan Nik M , Tewari Raj Deo , Baharuddin Salina Bt 
Published: September 2023

Deep saline aquifers offer significant potential for CO2 storage, with successful small-scale projects worldwide and major initiatives such as Gorgon in their early stages. In Peninsular Malaysia (PM) the daily CO2 production rate is expected to reach to the tune of ∼480 to 570 MMscf once the high contaminant gas fields are put on development. Several depleted hydrocarbon fields in PM region have been studied in the past for potential storage of the CO2 to be produced. Previously studies have been conducted on various depleted hydrocarbon fields within the PM region to assess their suitability for storing the anticipated CO2 volume. Nevertheless, the limited storage capacity and availability of these depleted reservoirs necessitate the exploration of alternative solutions. The deep saline aquifers in Peninsular Malaysia emerge as a viable option, as they can address the existing storage capacity limitations and facilitate the efficient development of high contaminant gas fields in the region, thereby enabling expedited monetization efforts.

A comprehensive screening matrix was devised to identify strategic saline aquifers, considering various factors such as fault density, presence of top seals, reservoir depth, thickness, extension, pressure, temperature, porosity, number of wells drilled, and data availability. This holistic approach enabled the identification of structures that met the screening criteria. Further analysis was conducted on these selected structures to determine their theoretical CO2 storage capacity. Based on the evaluated capacities and their potential for cluster development, the structures were ranked accordingly. This systematic process allowed for the identification and prioritization of saline aquifers with the greatest potential for CO2 storage and cluster development. This study involves the feasibility study of one such identified clusters comprising three drilled dry structures that were analyzed for their containment and capacity through extensive 3D data interpretation for generation of structural maps, mapping of major and minor faults, and attribute extraction, trap & seal analysis, faults & wells integrity analysis, 1D caprock integrity analysis, and effective storage capacity estimation through dynamic simulation.

The study concluded that two out of the three studied structures are associated with high trap risks and may not be suitable for injection & long-term storage of CO2. Further their close proximity to the regional fault would limit their viability for being potential open aquifer systems. The third structure which has well defined trap, seal & reservoir was found to be associated with relatively low effective CO2 storage capacity as based on the current analysis the storage capacity estimation was restricted to only one of the stratigraphic intervals only.

The adapted workflow and lessons learnt during this study can be applied to future saline aquifer screening studies involving dry wells in the region. This study further unfolds the necessity of adequate data availability to derisk the critical CO2 storage elements.