The Central Luconia province in the South China Sea, offshore Sarawak, features extensive development of Middle to Late Miocene isolated carbonate platforms. This study presents a regional seismic architecture - seismic facies review of platform flank geometries and off-platform depositional styles, with the goals of understanding their patterns and exploring the controlling processes. The information on flank steepness and predominant shedding direction is contextualized with respect to extrinsic and intrinsic factors of carbonate platform growth, including tectonics, eustatic sea level fluctuations, hydrodynamics and regional paleogeography. Results reveal that flank geometries are consistent throughout the Middle to Late Miocene. In the north of the province eastern flanks are dominantly aggradational, steep, and sediment-starved escarpments, whereas western flanks show more progradation and are accretionary in nature. Discrepancies from this pattern are observed among closely spaced platforms. The eastern aggrading flanks are interpreted to have been highly influenced by monsoonal wind driven currents. Further south in the province tidal currents, antecedent topography and syn-depositional tectonics were more important controls on platform architectural development. This study of regional processes and geomorphic products provides a basis for enhanced conceptual facies models and reservoir quality predictions.

Interdisciplinary data integration is key to top-quartile Well Reservoir Field Management (WRFM). In our field case, results from annual well-intervention activities were analyzed and integrated with production data and the regional-to-reservoir scale geological understanding of this carbonate gas field to improve the delineation of the gas-water contact (GWC) development and allow timely water shut off (WSO) at the optimal depths in the reservoir, while at the same time utilizing reservoir heterogeneities (such as horizontal baffles) to delay water breakthrough (WBT).The carbonate gas field is located in Central Luconia, with over 30 years of production history. Some wells have seen significant WBT and the field experiences an uneven rise of the GWC with production. To improve the GWC prediction, reservoir characterization work was aimed to capture the key heterogeneities that matter for flow: baffles vs. high-permeability conduits to water movement. As such, geological characterization focused on low-porosity zone correlation and platform margin & slope deposit interpretation along the flanks of the field, respectively.In order to understand the baffling nature of rock facies to fluid flow, low porosity zones were mapped across the field initially on seismic and well logs. In core, two types of low-porosity layers were observed: flooding-and exposure-related low-porosity layers. Both types of low-porosity layers show similar log signatures, but behave very differently during production . Flooding-related low-porosity layers are extensive and composed of fine-grained, argillaceous material. They form baffles that are capable of delaying water rise for several years. Exposure-related low-porosity layers, on the other hand, are composed of cemented, brittle limestones and are often associated with karsts and fractures. Their baffling capacity is limited and can even act as high-permeability conduits speeding up the GWC rise, when connected to karst dissolution.Platform margin and depositional-slope deposits were observed on seismic in the flanks of the field. These are inclined beds of potentially permeable deposits that have been shed from the carbonate platform during sea-level highstands. Commonly the strongest progradation and best-developed slope deposits are located on the leeward side, i.e. platform-top shedding and transport in the main paleo-current direction.Due to their inclined nature, they dip directly into the water leg and thus can act as conduits for water during production.

Extended Abstract Carbonate fields in Central Luconia have been delivering gas for about 30 years and petroleum engineers have been collecting large amounts of static and dynamic data by exploring, appraising and producing these Miocene platforms hosting the gas. The knowledge acquired is presently used to optimize existing field recovery, develop new fields without production data and reduce geohazards for drilling operations. It also provides an outstanding data set that can be extrapolated to understand the role of reservoir heterogeneities and hydrocarbon properties on production behavior and recovery in similar fields with less data outside Luconia.