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ABSTRACT: Turbidite and deep water systems of NW Borneo: outcrop and subsurface reservoir models

Crevello, Paul1, Mario Wannier2, and Felix Tongkul3
(1) Petroleum Geoscience International Consultants, LLC, Bandar S.B, Brunei 
(2) Shell US, Houston, TX
(3) University Malaysia, Sabah, N/A

Turbidites are relatively new exploration targets in deepwater depositional systems of Southeast Asia. Exploration has been exceptionally active off the major deltas of Borneo, such as the Baram, Mahakam and NW Sabah Shelf, where turbidite reservoir sands have demonstrated sustainable high flow rates. However, the complexity of predicting and imaging hydrocarbon-charged sands in syndepositional deformed basins has led to a low number of discoveries.

Direct reservoir analogs are exposed in the coastal ranges of NW Borneo, which are the same depositional systems that produce hydrocarbons only a few 10's of kilometers offshore. Turbidites occur within the Crocker, Temburong, and Setap Formations, which in outcrop range from Middle-Late Oligocene - Eocene(?) to Middle - Late Miocene.

The Crocker Formation represents a classic, unconfined basin-floor submarine fan complex. The sand-rich channel complex exceeds 300 m in thickness and covers more than 1000 sq km. Individual channel axis sands rarely average 3-5 m, while channel and sheet sands amalgamate up to 30-60 meters thick. Mud-rich levees were rarely preserved, and when present typically less than 3-5 meters and rarely exceed 10 m. Facies reconstruction, sand geometry, and lateral and strike extent of the fan supports an extensive complex of offlapping unrestricted channel-lobe fans.

The Neogene turbidite systems are sand-poor ponded basins that recorded linkage between sedimentation and tectonics. Turbidite channel sands and lobes thin and onlap or are truncated along active seafloor structures, faults and shale diapirs. Depositional cycles consist of mega-slumps, olistoliths and debris flows alternating with channel and sheet/lobe sands. The channel and lobe sands rarely exceed 3 m while amalgamated sands are less than 10-30 m. The linkage with lowstand shelfedge deltas and optimum reservoir sand quality is recorded in the Neogene system. These outcrop analogs will be compared with productive subsurface turbidite systems.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia