沧参1井热历史及成油气环境研究

STUDY ON THERMAL HISTORY AND OIL-GENERATED ENVIRONMENT FROM WELL CC1

本文通过Ｕ－Ｐｂ同位素地质年代学研究，指出沧参１井沉积地层中的物质来源是华北古陆；隐伏花岗岩侵位年龄为９９Ｍａ，来源于具下地壳特征的太古宙岩石的重熔。对奥陶系碳酸岩流体包裹体特征研究指出沧参１井流体包体类型可分为３大类、８个亚类，本区碳酸盐类岩石有机质丰富，应为一套生油储油较好的岩系。特别是通过不同深度１０个磷灰石样品裂变径迹表观年龄和径迹长度特征的研究，论述了本区古地温的变化，约在１４３Ｍａ前石炭二送纪地层中的磷灰石经历过完全的退火，这是二迭纪以下地层的第１次生油作用；９９Ｍａ花岗岩侵位，岩浆热对围岩中有机质的转化和油气的形成起了促进作用，这可作为第２次生油期；第三纪时因地壳下降，沉积了巨厚的第三系地层，这时磷灰石退火带范围（大致相当于生油带）约为１７００—３９００ｍ，古地温梯度为３．１℃／１００ｍ，这是本区第３次生油阶段。

U-Ph isotope geochronolgical study of core samples implies that the sedimentary strata arederived from North-China ancient land and the age of the hidden granite derived from the remelted Archean rocks with lower crust signature is 99Ma. Fluid inclusion investigation indicates thatthe Ordovician carbonate rocks are rich in organic matters and should be a better set of oil-generated rocks and reservoir. Based on fission track analysis of apatites from different depths and thepaleogeothermal variation, the authors suggest that there be at least three oil-generated stages.The range of annealing belt of apatite tracks and the paleogeothermal gradient in this well are1700-3900m (roughly corresponding to oil-generated belt) and 3. 1℃ /100m respectively afterTertiary sedimentation.