LOPEZ, LILIANA, and JEAN PASQUALI, Instituto de Ciencias de la Tierra, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela

ABSTRACT: Dispersed and Accumulated Organic Matter in Fractures: Primary Migration Evidences

Concentrated organic matter accumulated in fractures (organic rich fraction) and dispersed organic matter (total rock) of the source rocks of the Querecual and San Antonio formations of the Eastern Venezuelan basin were studied.

The distribution of organic matter was studied in polished sections. Sample were analyzed for total organic carbon (Ct), total bitumen and the n-alkane fraction within the bitumen. Dispersed and concentrated organic matter were analyzed separately, and the pertinent differences were established.

Concentrated organic matter, probably accumulated to due migration of dispersed organic matter into fractures, or low pressure zones is deficient in n-alkanes of low molecular weight. This fact is interpreted as the result of the migration process that allows the preferential movement of light components of low polarity. It seems that the products of kerogen maturation start their transformation to materials more like crude oils from their primary migration, stage that is to say, within the source rock.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.