Print this pagePiston Cores vs
Seapage Samples, Are They Representative in
Escandón, Maria de Jesús1,
Mario Limón2, Rebeca Navarro3 (1) Comesa Consultant,
The offshore deep water areas are known
as new frontiers of hydrocarbon exploration and represent a challenge to
establish correlation with producing fields, in order to calibrate the regional
geologic models in basin analysis. The main limitation, when using sea bottom
piston cores and seapage samples is related to the high percentage of
contamination from Biogenic organic matter, which could generate interference
or even mislead the interpretation of the origin of deep hydrocarbons reservoirs.
For this reason, it was necessary the previous recognition of these
differences, to evaluate the geochemical data of the Biogenic samples and those
with Thermogenic origin and exploratory potential. The comparison of C15+
fractions, Terpanes and Steranes Biomarkers (GC-MS) indicate that, even those
actually active migration path ways could have a different molecular
composition than the hydrocarbons in the reservoir. These differences could be
due to fractionation during migration, secondary alteration due to
biodegradation, cleaning by water flow, oxidation and/or segregation processes
during the sampling operation. The interpretation of C26Steranes by GC-MSMS and
Diamondoids showed to be less sensitive to high maturity, biodegradation
processes or other alterations. The integration of these techniques, have the
big benefit of facilitate the identification of mixtures of hydrocarbons with
different maturity due to different source rocks, which could be related to
superimposed Petroleum Systems, which are hardly differentiated with
conventional techniques. This methodology is a low cost investment, considering
the lowering of the risk which is achieved in the evaluation of the hydrocarbon
potential compared to the cost of drilling a well in deep water areas.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California