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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: De-Risking Deepwater Sarawak with
Controlled-Source Electromagnetic Imaging
By
1NewField
Exploration
In late 2005 Newfield and Petronas
Carigali acquired controlled source
electromagnetic imaging (CSEMI) data
over a series of rank wildcat prospects in
the Deepwater 2C block
, offshore Sarawak,
Malaysia. The CSEMI , 3D seismic and
remote sensing data were used as a risk
reduction tool to high grade a prospect for
drilling in late 2006. An exploratory well
has since been drilled.
The CSEMI survey acquired 390 km of data along 10 lines over 11 prospects and two dry holes. The prospects are Pliocene turbidites and large structures at the mid Miocene unconformity (MMU). Water depths were generally greater than 1000 meters with reservoir targets 1500 to 2500 meters below the sea floor. Sediments are primarily shales and sands with resistivities in the 1.5 to 2.5 ohm range. Data with a fundamental transmission frequency of 0.25 Hz were collected at approximately 1 km intervals along the lines.
A series of EM anomalies, 20 to 60 % above the normalized field amplitude, were found over a number of the Pliocene turbidite prospects and large MMU structural prospects, although not all of the turbidite or MMU prospects showed EM anomalies. In addition no EM anomalies were found at the two dry holes. Comparison of unconstrained and constrained 2.5D EM inversion, with the 3D seismic data, indicated that the EM anomalies coincided with prospects identified on seismic. There was good agreement where the EM lines crossed.
A positive test of the EM anomalies will
considerably reduce future exploration
risk in the block
.
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