Characterization of tar-like material and producible oil in Misoa C2 and C3 reservoir sands of the Area 2 South (Ceuta Field,Venezuela) |
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| Institution: | 1. School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, China;2. Mendocino County Museum, 400 East Commercial Street, Willits, CA 95490, USA;3. Noyo Hill House, 28953 Highway 20, Fort Bragg, CA 95437, USA .;4. Instituto de Ciências da Terra (ICT), Pólo da Faculdade de Ciências da Universidade do Porto, Departamento de Geociências, Ambiente e Ordenamento do Território, Faculdade de Ciências, Universidade do Porto, Porto, Portugal;5. Department of Earth and Space Sciences, 404-A Lappin Hall, Morehead State University, Morehead, KY 40351, USA;6. Federal Institute for Geosciences and Natural Resources, Department Geochemistry of Petroleum and Coal, Stilleweg 2, D-30655 Hannover, Germany;7. Indiana University, Indiana Geological Survey, 611 N. Walnut Grove Ave., Bloomington, IN 47405-2208, USA;8. University of Kentucky, Center for Applied Energy Research, 2540 Research Park Drive, Lexington, KY 40511, USA;9. State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology (Beijing), Beijing 100083, China;1. Geology Department, Faculty of Science, Port Said University, Port Said 42522, Egypt;2. Department of Mineral Resources and Rocks, Faculty of Earth Sciences, King Abdulaziz University, P.O. Box 80206, Jeddah 21589, Saudi Arabia;3. Geology Department, Faculty of Science, Mansoura University, El-Mansoura, Egypt;4. Geology Department, Faculty of Science, Helwan University, Cairo, Egypt |
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| Abstract: | Here we characterized asphaltic oil occurrences in the Misoa C2 and C3 reservoirs within Area 2 South of the Ceuta Field (Lake Maracaibo Basin, NW Venezuela). To perform the geochemical and petrological characterization of the C2 and C3 sub-units, which cover an interval in which tar-like material was detected, we analyzed core (18) and cutting (123) samples using the Rock-Eval 6 technique in reservoir mode. Samples were studied under fluorescence light and scanning electron microscopy (SEM), showing the presence of two charges of oils and the relationships within silica cements and clay minerals. To evaluate vertical inter-reservoir communication and lateral intra-reservoir continuity, we also studied 12 oil samples from wells in Area 2 South. Biomarkers and isotopic signatures were examined using gas chromatography-mass spectrometry (GC-MS) and isotope ratio mass spectrometry (IRMS). The results suggest that oil and core extracts belongs to a single family derived from two pulses of hydrocarbon generation from the La Luna source rock, which was deposited in a marine reducing environment. The oil samples are a mixture of a paleobiodegraded oil charge and a later fresh, more mature oil recharge. The geochemical analyses also evidence that the formation of heavy oil tar zones can be related to biodegradation and in-reservoir oil mixing, though other formation mechanisms for the tar are also feasible. Finally, the GC fingerprints of the oils are indicative of lateral reservoir continuities across the F-1 and F-2 faults and vertical communication between the Misoa C2 and C3 sub-units in Area 2 South, suggesting that tar occurrences do not act as permeability barriers within the two reservoirs studied. |
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| Keywords: | Tar-like material Paleobiodegradation Ceuta Field Misoa C2 and C3 reservoirs Generation pulses |
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