Uso de diamondoides en correlaciones crudo-crudo y crudo-roca madre petrolera

Abstract

Analyses of lower and higher diamondoids are discussed as novel methodologies to characterize thermally-altered, mixed and/or biodegraded hydrocarbon fluids generated from multiple sources in regional geochemical studies of petroliferous basins, as well as the extent to which those mixtures have occurred. More precisely, one of these methods is quantitative extended diamondoid analysis (QEDA), which is very useful in many cases to correlate the mature component of the oil to its source, an identification which is necessary for correct input of effective source rocks into basin models. QEDA consists of comparing relative concentrations of large diamondoid isomers and homologs in oils, extracts and condensates. Oil-oil and oil-source rock correlations using QEDA are much like biomarkers correlations. Moreover, another important organic geochemical tool is compound specific isotope analysis of adamantanes and diamantanes (CSIA-D), the determination of the carbon isotopic signature of a series of individual diamondoid species is a complementary method to tie high-maturity, complex and/or biodegraded fluids back to their sources. QEDA and CSIA-D are, in fact, applicable to any source-correlation problem. Example correlations using QEDA and CSIA-D from Ecuadorian Oriente and Progreso basins are discussed. Firstly, a principal aim of this research work is to investigate the geochemistry of hydrocarbon fluids and sedimentary rocks in the area of the Amistad field to determine the origin of the studied wet gases. Studied low-boiling condensates have similar gas chromatographic fingerprints while their compound-specific isotopic analyses of lower diamondoids (CSIA-D) indicate an oil-source correlation between them and Dos Bocas extracts. Sampled gases are mainly methane of biogenic origin except for that from the Delfín B-17X well, which might represent the thermogenic endmember gas signature of the Amistad gases. Secondly, another research paper encompasses an organic geochemical investigation on oils and sedimentary rocks from the southern coastal region of Ecuador that examines the hydrocarbon generation and accumulation in the strata of Progreso Basin Province. This petroliferous province represents an interesting area for an oil geochemistry study due to its non-elucidated petroleum systems. Classic biomarker, extended diamondoid, and isotope studies indicated that almost all oils from the Progreso Basin Province underwent biodegradation and were generated from multiple source rocks. Three families of oils were identified. Oil-source rock correlations suggest that the Socorro, Dos Bocas and San Eduardo formations can be considered as contributors to the studied oils. Finally, a third paper contains an integration of classical biomarker work with higher diamondoid examination to better characterize the petroleum systems in the north-central portion of the Sacha-Shushufindi Corridor in the Ecuadorian Oriente Basin. Classical biomarker results suggest mixing of pulses from distant siliciclastic and carbonate-rich Napo source rocks, with former oil charges being slightly biodegraded during the Paleogene and fresher Neogene pulses. These two types of Early-Late Cretaceous source rocks were deposited in similar paleo-environments with considerable and scarce contribution of land-plant material. Such differentiation of the two source facies types of the Napo Group is supported by results from uantitative extended diamondoid anal sis EDA.