Chaouche, Ahmed¹, Peter Gamwell¹, James Brooks²
(1) Anadarko Petroleum Corporation, The Woodlands, TX
(2) TDI-Brooks Int'I Inc, College Station, TX

ABSTRACT: Surface Geochemical Evaluation Of Green Canyon BLK.608, Gulf Of Mexico: A Comparison Of Seabed Seeps And Reservoir Hydrocarbon Fluids

Over 8,000 piston cores have been acquired in the deepwater Gulf over the last twenty years for surface geochemical exploration (SGE) studies. Despite these large core databases, very few case studies correlating the seep hydrocarbons obtained from shallow cores with the deeper reservoir fluids have been published. The promise of deepwater SGE is that macroseepage at the seafloor can provide critical information on oil generation, charge, and type/quality ahead of the drill bit.
The survey includes 12 piston cores acquired in 1999 before drilling in GC-608 (WD 4,300-ft). The purpose of the study was to collect seafloor seeps over deep-cutting faults to prove the existence of an active petroleum system. 3D seismic data were used to locate cores over faults associated with the surface anomalies. Each core was analyzed for gaseous and liquid hydrocarbons. Selected samples were analyzed for aliphatic and aromatic biomarkers.
The Marco Polo exploration well penetrated commercial hydrocarbon deposit and pointed to the close relationship with the positive seep anomalies. Biomarker analyses conducted on 3 "oil" core samples and 7 oils from Marco Polo reservoirs confirmed that they originate from the same source rock. We will present the good correlation between the surface and subsurface oil samples and demonstrate the value of integrating piston core geochemistry with pre-drill exploration geology and geophysics.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.