Unlocking the Complexities of Karstic Reservoirs Using Comprehensive Framework for Advanced 3D Static Modelling in JTN Carbonate Field in Central Luconia Province Academic Article uri icon

abstract

  • ABSTRACTCarbonate reservoirs, notably those within the Luconia Area (Sarawak) and Malaysia, constitute significant oil and gas resources and are crucial to CO2 Storage Assessment (CCS), strategically addressing karst‐related risks. These carbonate reservoirs demonstrate varying degrees of karstification, influenced by multiple diagenetic phases. Karstification involves the gradual dissolution of soluble rocks, predominantly carbonates, leading to distinct landforms such as dolines and sinkholes. Geomorphological studies during the 1980s have indicated that the impact of both local and regional tectonic movements, as well as fluctuations in sea levels, contributed to the karst development in the Central Luconia area. In this work, correlations between depositional concepts and karst formation are proposed, linked to syndepositional tectonics, influencing coral atoll growth and reef debris trajectory. Recent advancements utilising seismic attribute techniques, including spectral decomposition and variance for 3D geobody detection, have uncovered dendritic karst features within the JTN and Fx platforms. The geological configuration in the Central Luconia Province, offshore Sarawak, involves approximately 250 carbonate structures from the Middle to Upper Miocene age. This study integrates seismic data, petrophysical logs, regional geology, and core samples to construct a comprehensive stratigraphic model. The stratigraphic model aids in identifying potential karst networks within stratigraphic intervals, crucial for comprehensive reservoir architecture and fluid flow assessment in karstic intervals. The study explores fractal concepts to characterise 3D karst networks and utilises a deterministic workflow for 3D karstic static model construction. This research addresses geological uncertainties by exploring an innovative 3D karstic reservoir modelling methodology. The 3D karst network modelling employs a script‐based discrete fractured network (DFN) for identifying karst geobodies and utilises a fault seal analysis (FSA) approach to assess karst fills. These two methods aim to integrate 3D karst networks into a 3D conventional carbonate matrix model, establishing a dual‐properties modelling approach within a unified grid geological model. Additionally, it provides a foundation for analysing the interaction between carbonate matrix properties and karst networks, helping to address fluid flow uncertainties through three karsts fill assessment scenarios—opened, no‐flow and partial. Integrating the 3D karstic reservoir model with 3D dynamic modelling parameters, such as productivity heterogeneity as observed in production history, highlights the presence of karst networks for better reservoir characterisation solutions. This approach can help identify potential karst drainage systems or regions, offering a more refined assessment of the karst's impact on fluid flow compared to single property modelling in proven karstic fields. The findings offer valuable insights into the integrated matrix and karst networks approach, focusing on 3D karstic reservoir modelling assessments of depositional facies characterisation, seismic manifestations of karst networks and karst's fill analysis. The research recognises the challenges and opportunities of karstic reservoirs, highlighting the need for tailored strategies to address uncertainties in CO2 storage or hydrocarbon assessment. The multidisciplinary approach, which integrates advanced multi‐seismic attribute analysis and 3D reservoir modelling enhancement techniques, such as 3D grid refinement in specific regions to assess karst dimension uncertainty (minor karst), promises to improve the management of karstic carbonate reservoirs in the Luconia Area.

publication date

  • 2025

start page

  • gj.70010