Publications

A giant preserved pre-Cenozoic faulted synform has been identified in the Kangean area below the base Cenozoic unconformity. The structure is interpreted to have nucleated Paleogene extensional features that were subsequently inverted during the late Neogene, forming the prominent Central High. A high density of wells drilled in the Kangean area with an overall low exploration success ratio, suggests that the detailed processes leading to hydrocarbon charging are not completely understood. The thermal measurements available from those wells provide the opportunity to calibrate a 3-D thermal model, and investigate if the presence of the pre-Cenozoic structure impact the thermal regime affecting the Cenozoic strata and have hampered exploration efforts to date. Built over an area of 300 km E-W and 200 km N-S, centred over the Central High, the 3-D model reveals the heat flow at the base Cenozoic unconformity to be broadly organized at present in three distinct latitudinal thermal domains. This distribution appears to be a function of the burial depth of the actual basement below the unconformity. In the North and South thermal domains, where the basement lies near the base Cenozoic unconformity, high heat flows are observed (70-80 mW/m2). In the central thermal domain, where the basement is buried below the pre-Cenozoic synform, lower heat flows are seen to occur (< 70 mW/m2), with the lowest computed values aligned along the axis of the synform itself (55-60 mW/m2). We interpret this negative thermal anomaly as a result of heat losses that affect the heat flow as it travels through the preserved sedimentary column of the syncline. The anomaly degrades specially the Northern Platform in terms of source rock maturity and triggers a revision of the charging model for the Pagerungan Field.