| This study uses drilling geology,logging data and geochemical sample analysis to study the genetic type of natural gas and its origin,the distribution of source rocks,and the gas generation intensity of the coal-measure source rock in Xujiahe formation with the methods of organic geochemistry and resource evaluation.Furthermore,the resource potential of the source rocks is also evaluated in this paper.The following conclusions are obtained:?1?In Bazhong area,the natural gas in the Xujiahe Formation is mainly coal-type gas and sourced from the coal-measure source rocks in the Xujiahe Formation.But in Tongnanba area,the natural gas is mixed with the underlying marine oil-type gas,whereas the methane hydrogen isotope of gas is relatively light,which is obviously different from the marine oil-type gas,so it is mainly sourced from the Xujiahe Formation.?2?The source rocks in Xujiahe formation all have high organic matter abundance,and the average value of TOC is 2.43%.The type of kerogen is mainly type-?,few type-?2,and The maturity level is in late stage of high maturity and early stage of post mature,mainly generate dry gas.?3?The cumulative thickness of coal-measure source rocks in xujiahe formation is 50m330m.Dark mudstones mainly exist in the 3rdd and 5th member of Xujiahe Formation,which are mainly distributed in the west of the research area and the central of the Tongnanba area.The coal seams mainly exist in the5th member of Xujiahe Formation,which are mainly distributed in the wellblock YL17?eastern part of Bazhong?.?4?The gas generation intensity of coal-measure source rock?include dark mudstone and coal seam?is 5×108m3/km235×108m3/km2,and the quantity of gas generated and the total resources are 54638.56×108m3 and2731.9×108m3.Among them,the resources contributed by the coal seams is1217.9×108m3,accounting for 44.6%of the total resources.Gas producing well is mainly situated in the gas generation center and its circumferentia. |
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