Geochemistry and origin of Ordovician oils in the Rewapu Block of the Halahatang Oilfield (NW China)

Petroleum Science

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[1] 0000 0004 0644 5174, grid.411519.9, State Key Laboratory of Petroleum Resources and Prospecting, College of Geosciences, China University of Petroleum, 102249, Beijing, China;Key Laboratory of Exploration Technologies for Oil and Gas Resources (Yangtze University), Ministry of Education, College of Resources and Environment, 430100, Wuhan, Hubei, China;Key Laboratory of Exploration Technologies for Oil and Gas Resources (Yangtze University), Ministry of Education, College of Resources and Environment, 430100, Wuhan, Hubei, China;0000 0004 0644 5174, grid.411519.9, State Key Laboratory of Petroleum Resources and Prospecting, College of Geosciences, China University of Petroleum, 102249, Beijing, China;Research Institute of Petroleum Exploration and Development, Tarim Oilfield Company, PetroChina, 841000, Xinjiang, Korla, China;

关键词: Biodegradation;    Water washing;    Oil charging process;    Ordovician;    Tarim Basin;   

DOI  :  10.1007/s12182-018-0284-4

来源: publisher

【 摘 要 】

The oils in the Rewapu Block of the Halahatang Oilfield in the Tarim Basin (northwestern China) were geochemically analyzed by gas chromatography–mass spectrometry to investigate their origin and possible secondary alteration. The physical properties and chemical compositions of these Ordovician oils vary greatly, ranging from light to extremely heavy oils. All these oils belong to one single population and were derived from same source kitchen/bed. The differences in their chemical compositions and physical properties mainly result from secondary alteration of oils that were charged during the early phase of trap formation. The thickness of Upper Ordovician and Silurian caprocks of oil reservoirs in the Rewapu Block is higher than that in the north part of the Halahatang region, and therefore, significant biodegradation process is prevented. Compared to heavy oils in the north part, the Rewapu oils are dominated by light oils with no 25-norhopanes and no GC–MS “hump” (UCM: unresolved complex mixture) on the chromatographic baselines. The heavy oils in Wells RP7 and RP101C were primarily influenced by water washing since apparent reduction of alkylated dibenzothiophenes was observed. The local geological background favored the water washing alteration. The reservoir geochemical study has practical application in hydrocarbon exploration and predicts the nature of oils in this oilfield.

【 授权许可】

CC BY