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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association


14th Annual Convention Proceedings (Volume 1), 1985
Pages 453-495

Discovery of the Cunda Gas Field, Bee Block, North Sumatra: An Integrated Geologic/Seismic Stratigraphic Case History

M. D. Burnaman, R. B. Helm, C. R. Beeman


Reinterpretation of geophysical and geological data on the Cunda structure, located 5 kilometers northwest of the giant Arun field, resulted in drilling the Cunda-A2a gas discovery in 1984. Production is from a Peutu/Bampo limestone of Upper Oligocene to Lower Miocene age. Cunda-A1, drilled in 1974 on the crest of the same paleohigh did not encounter any Peutu limestone implying that the crest of the structure was too high to support reef growth or that it had been stripped of Peutu deposits. Subsequent reevaluation of seismic and gravity data indicated that the Cunda paleohigh had probably existed since Oligocene time and that limestone deposition west of Arun took place as early as Upper Oligocene. Structural mapping showed significant closure downdip from Cunda-A1.

Relative amplitude processing with careful attention to quality control on 1977 vintage seismic lines permitted the delineation of five seismic facies in the prospect area. The relatively high amplitude of the reflection on the flanks of the structure at the proposed reservoir level indicated that high velocity limestone could be present between the lower velocity Baong and Peutu/Bampo shales. Incorporation of the reflection amplitude and character with synthetic seismograms and 2D seismic models made with wireline log data from nearby wells suggested that up to 320 feet of limestone could be present on the east flank of the Cunda structure.

The Cunda-A2a discovery well drilled 336 vertical feet of limestone overlying a thin conglomeratic sandstone on Bampo shale confirming the interpretation. An open hole drillstem test flowed gas at a rate of 10.5 MMSCF/D on a frac12.gif (855 bytes) inch choke.

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