Hydrocarbon accumulation process of the deep to ultra deep reservoirs in Fuman oilfield,Tarim Basin
The platform area of Tarim Basin possesses a vast hydrocarbon resource potential in deep to ultra-deep reservoirs.Tarim Basin has experienced a complex of hydrocarbon accumulation in the Ordovician Yijianfang Formation and Yingshan Formation in Fuman oil-field.Meanwhile,there is a significant difference in the planar distribution of hydrocarbon phases.Based on micro-area U-Pb isotope dating of carbonate cement and crude oil inclusions as well as carbonate veins,this study has determined three stages of fracture-cave type vein filling in reservoirs of Fuman oilfield,three stages of crude oil charging and one stage of natural gas charging.Specifically,the Stage-1 of crude oil charging occurred during the Middle Caledonian Period(473.3-447.4 Ma),the Stage-2 spanned from the Middle Devonian to the Late Devonian Period(348.2-273.9 Ma),the Stage-3 occurred during the Early Indosinian to Yanshanian Period(217.6-205.2 Ma),and the natural gas charging occurred on a large scale during the Late Yanshanian to Himalayan(90-20 Ma).The three stages of fracture-cave type vein filling correspond to the three stages of crude oil charging and tectonic activity.There are differ-ences in the maturity and type of paleo oils charged in the southern and northern parts of Fuman oilfield,which are primarily influenced by variations in the thermal evolution of source rocks in the Cambrian Yuertusi Formation in different areas of the oilfield.The evolu-tionary processes of the Cambrian source rocks and the timing of tectonic activities in the platform area exhibit temporal and spatial cor-relations with the four phases of hydrocarbon charging.These research findings contribute to an enhanced understanding of the hydro-carbon accumulation mechanism and hydrocarbon enrichment regularity of deep to ultra-deep carbonate reservoirs.
fluid inclusionisotope datingdeep oil and gascarbonate rockTarim Basin
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