Deep Burial Diagenesis of Luconia Platform (Sarawak, Borneo) as the Main Control of Reservoir Properties

Conxita Taberner¹, Mateu Esteban², Georg Warrlich³, Marta Rejas⁴, and Jan-Henk Van Konijnenburg^5
1 Institute of Earth Sciences "Jaume Almera", CSIC, Barcelona, Spain
² Carbonates International Iberia, S. L
³ Shell Carbonate Team,
⁴ CSIC, Barcelona,
⁵ Sarawak Shell Bhd,

The carbonate reservoirs from the Luconia Province (Sarawak, Borneo) had been traditionally interpreted as formed due to dolomitization in the hypersaline lagoons of atoll reefs during early diagenesis. Prediction of porosity distribution was then depending on an early “hypersaline” dolomitization model. Petrographical and geochemical investigations in samples from four cores in the region have enabled the reinterpretation of the dolomitization model. Dolomitization in the atoll reefs and ramps below was mostly controlled by the inflow of deep-seated fluids along fractures. Mixing of formation waters with deep-seated aquifers caused preferential dissolution and / or dolomitization of the mud-supported facies. Dolomitization occurred at burial stages, post-dated pressure-dissolution and immediately pre-dated oil-charge. Dolomite and late calcite cements, the last occurring below oil-water contact, can be easily explained as precipitated from reservoir waters. The interpretation of dolomitization as occurring during late burial has major implications for the interpretation of predicted porosity distribution patterns. The authors would like to thanks PETRONAS for their support.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005