| Asphalt,an indispensable in the process of formation and evolution of oil and gas products,has implications for distribution and exploration in oil and gas.Simultaneously,The natural asphalt,as an organic fluid,is associated with the formation of some metal deposits in sedimentary basins,especially the MVT deposits.The Pb-Zn deposits in Dengying Formation in the northern margin of the Sichuan basin,which belongs to the Mississippi Valey-type?MVT?Pb-Zn deposits.and a large amount of asphalt is present in these deposits.Based on the regional geological background,this paper usingfield geological survey,indoor organic geochemical analysis,scanning electron microscopy and inclusions Raman analysis to reveal the relationship between the accumulation of oil and gas reservoirs and the mineralization of MVT lead and zinc deposits.The study found that there were two paleo-karst interfaces in the Dengying Formation,and the deposits of lead-zinc and the ancient oil?gas?were obviously controlled by the paleoclimatic karst.Through the distribution range of asphalt,restoring the ancient reservoir distribution,to light three sections for community development,there are two separate oil pool,light three sections of the upper part of the ancient reservoir in study area wide,Moreover,the lower of the ancient reservoir only in central and western development in the study area,the ancient reservoir in the east because of the influence of the ancient karstification smaller gradually thin out.Research area of MVT lead-zinc deposits are output in the range of the ancient oil and gas reservoir,also saw a large amount of asphalt filling.The lead-zinc and asphalt with "sometimes-complex mix-and-match I in you" space output characteristics,show the oil and gas reservoirs and lead-zinc deposit exists in the space characteristics of symbiosis and separation.This study also found that the organic matter of the asphalt and the shale was derived from the lower organisms such as algae,through the asphalt-the shale the characteristics of biomarker,Which was from algae to hypoxia and sedimentary environment have certain salinity reduction environment.Asphalt and shale are highly consistent both in terms of maternal properties,sedimentary environment and maturity,indicated that the origin of organic matter is related,that is,the source of asphalt organic matter is the mudstone of the Lower Cambrian Guojiaba Formation.According to the effect of "geoluminescent layer" on the geochemical parameters of biomarker compounds such as n-alkanes and paraffins,it is shown that the migration direction of oil and gas in the region is well consistent,Direction from east to west.The content of Pb and Zn in asphalt is much higher than that of crustal clark,and the average values are 313×10-6and2934×10-6,respectively,which is much higher than that of Pb(2.0×10-6)and Zn(13×10-6)content,which is fully capable of providing lead and zinc for lead and zinc mineralization.Indicating that the crude oil itself can become part of the ore-forming fluid or directly into the ore-forming fluid.It is found sphalerite,galena and other metal inclusions in the asphalt,while the asphalt was discovered in sphalerite and other minerals.Asphalt and sphalerite in the micro-show "you have me,I have you?sometimes-complex mix-and-match I in you?" specialty.It also suggested that the ore-forming fluids of lead-zinc ores were comed from ancient reservoirs.In addition,there are sphalerite,galena and other metal inclusions in the source rock of asphalt,lead-zinc mine and asphalt has good consistency in the migration direction,which show the characteristics of migration from east to west,further confirming the ore-forming fluids of lead-zinc ores come from ancient reservoirs.The research demonstrated that the lead-zinc deposits and the ancient reservoirs in the study area showed the characteristics of "sometimes-complex mix-and-match I in you" in both the macroscopic space and the microscopic mineral deposits.Lead-zinc deposit exists in the same transport,homology characteristics,that is,the ancient reservoir of reservoir fluid is lead-zinc ore ore-forming fluid. |
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