Lacustrine Source Evaluation Updated: Applying South Atlantic Successes to SE Asia
Dickson, William¹; Schiefelbein, Craig F.²; Christ, Janice M.³
¹DIGs, Houston, TX.
²Geochemical Solutions International (GSI), Houston, TX.
³Geological Consulting, The Woodlands, TX.
Explorationists have long understood the value of lacustrine source rocks in Paleogene basins around SE Asia. Schiefelbein et al., 1997 discussed their analysis of 350 oils as classified into lacustrine, deltaic, terrigenous, marine, and marine carbonate-derived. Besides typical early Paleogene lacustrine source intervals, many basins contain shallower Neogene coals and marine intervals which are often mature. Improved geophysical imaging is clarifying the volume of underlying Mesozoic basins bearing their own source intervals. Each interval contributes to the detected hydrocarbon signal that can mask lacustrine indicators amidst overprinting from both younger and older intervals with their own marine and/or coaly signatures.
Advancing geochemical and basin analysis techniques are improving our ability to identify the signatures in well and surface samples and determine the maturation histories of lacustrine- (and other) sourced hydrocarbons. The authors developed applications of these techniques in basins along the South Atlantic margins of Brazil and West Africa. Typical problems include unravelling complex maturation or migration histories in fields with multiple source intervals or similar source intervals yielding oils with different physical characteristics (gravity, sulphur content, etc). A key application was the determination from post-salt samples and piston core data of pre-salt source potential in a region without pre-salt wells.
We first provide overview examples of the techniques which include whole-oil analysis including diamondoid fractions; multi-variate statistics; and incorporation of multi-disciplinary data. From regional sediment thickness mapping of SE Asia, we revisit basins that illustrate parallels to our South Atlantic experience. We conclude with an assessment of sample adequacy and steps required to address our questions.
AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012