Southeast Asian Carbonate Systems
SE Asian carbonate formations have been reviewed with the aim of understanding the influence of tectonics on their development and reservoir potential through the Cenozoic. Regional tectonics, via plate movements, extensional basin formation, and uplift, was the dominant control on the location of carbonate deposits. These processes controlled the movement of shallow marine areas into the tropics, together with their emergence and disappearance. Although ∼ 70% of the 250 shallow marine carbonate formations in SE Asia were initiated as attached features, 90% of economic hydrocarbon discoveries are in carbonate strata developed over antecedent topography, of which more than 75% were isolated platforms. Faulted highs influenced the siting of nearly two thirds of carbonates developed over antecedent topography. Around a third of carbonate units formed in intra- and interarc areas; however, economic reservoirs are mainly in backarc and rift-margin settings (∼ 40% each). Carbonate edifices show evidence of syntectonic sedimentation through: (1) fault-margin collapse and resedimentation, (2) fault segmentation of platforms, (3) tilted strata and differential generation of accommodation space, and (4) modification of internal sequence character and facies distribution. The demise of many platforms, particularly those forming economic reservoirs, was influenced by tectonic subsidence, often in combination with eustatic sea-level rise and environmental perturbations. Fractures, if open or widened by dissolution, enhance reservoir quality. However, fracturing may also result in compartmentalization of reservoirs through formation of fault gouge, or fault leakage via compromised seal integrity. This study will help in reservoir prediction in complex tectonic regions as the petroleum industry focuses on further exploration and development of economically important carbonate reservoirs.
Figures & Tables
The Cenozoic carbonate systems of Australasia are the product of a diverse assortment of depositional and post-depositional processes, reflecting the interplay of eustasy, tectonics (both plate and local scale), climate, and evolutionary trends that influenced their initiation and development. These systems, which comprise both land-attached and isolated platforms, were initiated in a wide variety of tectonic settings (including rift, pas-sive margin, and arc-related) and under warm and cool-water conditions where, locally, siliciclastic input af-fected their development. The lithofacies, biofacies, growth morphology, diagenesis, and hydrocarbon reser-voir potential of these systems are products of these varying influences. The studies reported in this volume range from syntheses of tectonic and depositional factors influencing carbonate deposition and controls on reservoir formation and petroleum system development, to local studies from the South China Sea, Indonesia, Kalimantan, Malaysia, the Marion Plateau, the Philippines, Western Australia, and New Caledonia that incor-porate outcrop and subsurface data, including 3-D seismic imaging of carbonate platforms and facies, to un-derstand the interplay of factors affecting the development of these systems under widely differing circum-stances. This volume will be of importance to geoscientists interested in the variability of Cenozoic carbonate systems and the factors that controlled their formation, and to those wanting to understand the range of po-tential hydrocarbon reservoirs discovered in these carbonates and the events that led to favorable reservoir and trap development.