The Tectonic Overprint and Evolution of Large-Scale Carbonate Platforms in Central Luconia, Offshore Sarawak, Malaysia

Ting, King King¹; Pierson, Bernard J.²; Al-Jaaidi, Omar³
¹Sarawak Shell Berhad, Miri, Malaysia.
²South-East Asia Research Laboratory, SEACARL, University Teknologi PETRONAS, Tronoh, Malaysia.
³Qatar Petroleum, Doha, Qatar.

The Luconia province developed in a complex tectonic setting related to the opening of the South China Sea, about 45 Ma ago, with rifting following the initial collision of the Indian plate. A detailed study on two large-scale carbonate platforms, more than 100 km2 in size and 1 km thick, provides insights into the variation of growth styles of these platforms. This study involved 3D seismic stratigraphic analysis, which includes seismic reflection configuration, shape, and combinations of different amplitude extractions, coupled with local calibration with well logs to establish the sequence stratigraphy and understand the controlling factors of platform evolution.

The study of stratal patterns and association with fault patterns clearly indicate syndepositional movements took place during the growth of the platforms. The development of certain stratal patterns can be attributed to differential, fault- controlled tectonic subsidence and reflect abrupt lateral and vertical platform margin and slope facies changes that coincide with the position and orientation of faults. The configuration of faults strongly control the plan-view shape and dimensions of platforms and have created crescent shaped isolated platforms.

The following growth patterns have been observed across the platforms:

(1) Platforms that initially developed on closely- spaced horsts, coalesced into a composite platform. The apparent ‘sagging' of inner platform strata that decreases up-section indicates possible differential tectonic movements across the platform during growth.
(2) Platform fragmentation takes place at the same locations where the platform initially experienced localized subsidence and is attributed to the reactivation of major basement faults. Continuous fragmentation has led to the permanent separation of parts of the platform in a late phase.
(3) Platform contraction and drowning occurs during a rapid subsidence stage.

These observations and interpretations have added to the understanding of the facies distribution, platform morphology, and overall stratigraphic development of Miocene carbonate platforms in Central Luconia. This new information is crucial for understanding reservoir development and facies changes.

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012