Tectonic and Depositional History of Salawati Basin, Papua - Indonesia : Implications to the Occurrences of Miocene Kais Carbonate Play Types

Awang Harun Satyana
Indonesia's Implementing Body for Upstream Oil and Gas Business, Jakarta, Indonesia

Salawati Basin, Papua in Eastern Indonesia has been producing oil and gas from Miocene carbonate reservoirs for almost sixty years. First discovery occurred in 1936 from Klamono structure of Late Miocene Kais carbonate reefal build-up (later called as Kasim play type). Important discoveries occurred during 1970s when the basin was intensively explored. Many fields of carbonate build-ups were discovered, including the Kasim and Walio fields which ever became the biggest oil producers in Southeast Asia for build-up play. Significant discoveries occurred again during 1990s when discoveries of Matoa, Southwest “O”, and “Matoa-20” took place. Their plays are different : faulted Kais platform carbonates (Matoa play type), subtle very low-relief Kais build-up (Southwest “O” play type) and subtle intra-Kais platform build-up (Matoa-20 play type). Recent exploration activities in the Salawati Basin still targeting all of these plays.
Salawati Basin underwent tectonic reversal during the Miocene-Pliocene as a response to the advent of the Sorong Fault megashear. During this period, the tilting of the basin rotated clockwisely from tilting southward, through southwestward, and eventually northward. The Kais platform development and carbonate sedimentation were strongly controlled by this basin's polarity change. Most of the Matoa-20 and Southwest “O” play types developed in the lagoonal facies when the basin tilted southward. Growth of the classical Kasim play type occurred when substrates of the reefal build-ups subsided slightly due to the change of basin's polarity southwestward. As the basin rapidly tilted northward, compensating faults were formed and resulted in faulted platform of Matoa play type.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece