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Mene de Mauroa, Venezuela

Marquez G.,University of Huelva | Escobar M.,CARBOZULIA | Escobar M.,University of Zulia | Lorenzo E.,University of Huelva | And 3 more authors.
Fuel | Year: 2016

Here we analyzed oil samples from 35 wells in the Ceuta Southeast Area (Lake Maracaibo Basin, northwestern Venezuela) in order to evaluate lateral intra-reservoir continuity in the Misoa B4 unit. Biomarkers, isotopic signature, and also V and Ni were examined using gas chromatography-mass spectrometry (GC-MS), isotope ratio mass spectrometry (IRMS), and inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Multivariate statistical analysis was also applied to obtain useful information from geochemical data. On the basis of the characterization of these samples, we conclude that they all fall into various oil families derived from two pulses of hydrocarbon generation, migration and accumulation from the calcareous La Luna source rock, deposited in an anoxic marine environment under reducing conditions. Thus, these oils are a mixture of an earlier biodegraded, less mature oil charge and a later fresh non-biodegraded oil recharge. In addition, we applied asphaltene pyrolysis to one (LG-62) of the three "anomalous" oils. The LG-62 sample was confirmed as an almost "pure" paleobiodegraded end-member, whereas the VLF-3020 oil was tentatively classified as the unaltered end-member oil-type. Finally, the GC fingerprints and Fourier Transform Infra Red (FTIR) spectroscopic indices of the oils were used to detect minor variations in composition that are indicative of reservoir compartmentalization. © 2015 Elsevier Ltd. All rights reserved. Source

Geochemical evaluation of oil from a well recently drilled in the southeast area of Maracaibo Lake (FRA-1X, Franquera oil field) and its comparison with 5 crude oils from nearby fields, led to the conclusion that these geochemically correlated marine mature oils could be the result of the mixture into the reservoir of petroleum formed by two pulses of generation of the La Luna Formation source rocks, which fed the study area in different geological periods (Eocene and Miocene-Recent). Source

Escobar M.,CARBOZULIA | Escobar M.,University of Zulia | Marquez G.,University of Huelva | Suarez-Ruiz I.,CSIC - National Coal Institute | And 3 more authors.
International Journal of Coal Geology | Year: 2016

The aims of this work were to carry out a combined petrographic, palynofacies, and organic geochemical study of twelve drill-core samples collected from the lowest coal seams in the Paleocene Marcelina Formation (Paso Diablo mine, Guasare Basin, northwestern Venezuela), to characterize crude oil samples from three wells in the nearby Amana Field and to evaluate oil-source correlations of these crude oils with the Paso Diablo coal extracts. The coals under study were classified as high volatile bituminous A or at the B-A boundary, and showed vitrinite contents between 50.0 and 89.4 vol.%, liptinites ranging from 1.4 to 24.2 vol.%, and inertinites in the 6.2–30.8 vol.% range. Results from organic geochemical investigations indicate that the Guasare coals were generated in a limno-telmatic to telmatic zone under fluctuating oxygen conditions. A Type III kerogen with relatively high hydrogen content and a thermal maturity corresponding to the early oil window are proposed for these coals as supported by Rock-Eval and petrographic data, as well as biomarker interpretations. Oil generation potential from Marcelina Formation coals is probably due to the perhydrous nature of the vitrinite, high bitumen contents, and considerable liptinite concentrations, mainly oil-prone resinites and exsudatinites. Palynofacies observations denote a dominance of psilate pollen grains related to angiosperm plants and, as expected, Type III kerogens or humic coals in the studied seams, the parent material of which contained a significant contribution of algae. The non-detection of 18α(H)-oleanane does not preclude the fact that angiosperms are the dominant plants in the Guasare paleomire. On the other hand, the characterization of the Amana oils suggests that they all fall into a unique oil family; the presence of 25-norhopanes in them could indicate paleobiodegradation and mixing from various hydrocarbon charges in the reservoir. Thus, the crude oils from the Amana Field seem to be a mixture of one or more oil charges from the early mature marine carbonate source rocks of the La Luna Formation, deposited under anoxic reducing conditions, and a later pulse of hydrocarbon generation which originated from an unknown – so far – nonmarine source rock. In this regard, hydrocarbon liquid derived from the lowest Marcelina coal seams may be tentatively identified as the latter oil charge. Also, this work delineates some components of a currently subcommercial and hypothetical Tertiary petroleum system – identified and named as Marcelina/Misoa C5(.) – in the Lake Maracaibo region. Finally, the coalbed gas contents of sampled coals were determined. © 2016 Elsevier B.V. Source

Escobar M.,CARBOZULIA | Escobar M.,University of Zulia | Marquez G.,University of Huelva | Azuaje V.,Pacific Stratus Energy Colombia Ltd. | And 2 more authors.
Fuel | Year: 2012

This work is an analysis of crude oil samples from thirty wells in the Alturitas Field (Lake Maracaibo Basin, western Venezuela). Different biomarkers, ten trace elements, and porphyrins were analysed using GC-MS, ICP-OES and UV-visible techniques, respectively. The characterization of these crude oils leads us to conclude that they all fall into a single non-biodegraded oil family derived from a single pulse of hydrocarbon generation, migration and accumulation from the thermally mature calcareous La Luna source rock deposited in an anoxic marine palaeoenvironment under reducing conditions. The main objective of this work is to present a secondary oil migration model for the Marcelina reservoir of the Alturitas Field. The multivariate statistical study of trace-element concentrations, porphyrin contents, and polar compound proportions shows that these parameters can be split into two groups. The first group (Cd, Cu, Mo, Fe, P, Zn, Ca, and Mg) indicates a chalcophic association (Cd, Cu, Mo, and Zn) or colloidal complexes with naphthenic acids (Ca, Mg, and Fe). The other two trace elements (V and Ni), together with porphyrins and polar compounds, reveal that oil compositions has been affected by geochromatography, indicating a highly probable secondary migration pathway along a preferential axis orientated southeast to northwest. © 2012 Elsevier Ltd. All rights reserved. Source

Montilla L.A.,Pdvsa | Martinez M.,Central University of Venezuela | Marquez G.,University of Huelva | Escobar M.,CARBOZULIA | And 5 more authors.
Geochemical Journal | Year: 2013

A geochemical and chemostratigraphical study was undertaken on Campanian-Maastrichtian sedimentary rocks (the Colón -Mito Juan sequence and the upper La Luna Formation) in the southwestern Maracaibo Basin, Venezuela. The objectives of this work were to determine the paieoenvironmental and physico-chemical characteristics of the Colón -Mito Juan sequence and its possible subdivision into chemofacies and to study the main chemical differences between the Colón , Mito Juan, and La Luna Formations within the study region. One hundred and ninety-one rock samples were collected, and bulk inorganic geochemistry (TiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, P 2O5, C, S, Rb, Cs. Ba, Sr, Th, U, Y, Hf, Mo, V, Cr, Co, Cu, Ni, Sc, La, Ce, Nd, Sm, Eu, Yb, Lu, As, Sb, Zn, and Be) was analyzed by instrumental neutron activation analysis or inductively coupled plasma-atomic emission spectroscopy; total sulfur and carbon analyses were performed by a LECO SC-432 apparatus and coulometry, respectively. Multivariate statistical techniques were applied to evaluate correlations within this group ol variables. Using cluster-constrained analysis, eight subdivisions, or chemical facies, were defined: Two chemofacies differentiating the intervals controlled by biogenic deposition and by the predominant clastic contribution; three chemofacies correlating with the lithologic units (La Luna, Colón , and Mito Juan); and another three chemofacies related to changes in the paleoredox conditions along the stratigraphic column. All of the units studied were deposited under a relatively constant climate regime, and the composition of the sediment source showed no significant changes. The prevailing physico-chemical regime was disoxic-oxic, with a trend of increasing oxygen concentrations towards the top of the column. Copyright © 2013 by The Geochemical Society of Japan. Source

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