Molecular Geochemistry as a Tool for Reservoir Alteration Processes Predication

Abstract

A recent integrated molecular and isotope geochemistry and petroleum engineering approach has yielded new parameters for reservoir charge history, water washing, biodegradation and gas to oil ratio (GOR).  A total of 14 light oil samples were investigated utilizing two gas chromatography (GC) techniques for their detailed light hydrocarbon (n-C4 to n-C10) composition and whole-oil GC fingerprinting. The samples were also assessed by liquid chromatography for their saturates, aromatic and polar fraction concentrations. The first two fractions were assessed for their biomarker and carbon isotope compositions.  The oils were classified based on their inferred source rock and charge history into three groups. Two groups are attributed to two different source rocks, and the third represents a mixture of two previous groups. The biomarker concentrations were low due to the high thermal maturity; however, they elucidate similar conclusion drawn from the light hydrocarbon GC results. The isotope data did not illustrate great variations among the samples possibly because of similarity in the source rock age and thermal maturity.  The study elucidates a new geochemical ratio for water washing and GOR predictions. The whole-oil fingerprinting method indicates at least five reservoir compartments.  The light hydrocarbon assessment implies water washing effects increase toward the north. These data positively correlate with C11 hydrocarbon compound ratios, API gravities and GOR. These new relationships allow for utilizing molecular geochemistry in predicting reservoir engineering parameters. Such application opens the door for better geochemical data optimization to understand reservoir alteration process.

AAPG Datapages/Search and Discovery Article #90337 ©2019 AAPG Middle East Region GTW, Regional Variations in Charge Systems and the Impact on Hydrocarbon Fluid Properties in Exploration, Dubai, UAE, February 11-13, 2019