塔中隆起志留系沥青砂岩油气储层自生伊利石K-Ar同位素测年研究与成藏年代探讨

据自生伊利石K-Ar同位素测年技术对塔中隆起志留系沥青砂岩油藏成藏年代的测定,并与孔雀河地区进行对比.塔中隆起及孔雀河地区志留系沥青砂岩的自生伊利石年龄为383.45～203.96 Ma,表明主要为晚加里东—早海西期和晚海西期成藏,位于盆地边部的乔1井、孔雀1井及龙口1井、英南2井相对较早(383.45～271.20 Ma),主要为晚加里东—早海西期成藏,位于盆地中心的塔中37井、塔中67井、塔中12井及塔中32井相对较晚(203.96～235.17 Ma),主要为晚海西期成藏,部分井如塔中23井、塔中30井相对较早(293.54和296.31 Ma),为早海西期成藏.自生伊利石年龄与沥青砂岩厚度具有较好的对应关系,说明古构造格局可能是主要的成藏控制因素之一,位于沉降中心及其周围的古油藏如乔1井、孔雀1井成藏较早.测年结果不仅与油气系统等常规油气成藏史研究成果基本一致,而且还进一步反映了油藏形成时间上的差异.

K-Ar isotopic dating of authigenic illite and its application to the investigation of hydrocarbon accumulation history of the Silurian bituminous sandstone reservoirs in the Tazhong uplift, Tarim basin

K-Ar isotopic dating method of authigenic illites is used to estimate the age of the Silurian bituminous sandstone reservoirs in Tazhong uplift of Tarim basin and the results are compareied with that of Kongquehe area. The age of authigenic illites in the Silurian bituminous sandstones in Tazhong uplift and Kongquehe area ranges from 383.45 to 203.96 Ma, indicating that the Silurian ancient oil pools were formed during the late Caledonian-early Hercynian and late Hercynian. For Qiao-1, Kongque-1, Longkou-1 and Yingnen-2 wells, located in the outer part of the basin, the age of authigenic illites is in the range from 383.45 to 271.20 Ma, indicating a late Caledonian-early Hercynian reservoiring; while for TZ-37, TZ-67, TZ-12, and TZ-32, wells located in the central area of the basin, it is about 203.96 -235.17Ma, indicating a pooling in the late Hercynian. However, for some of the wells in the central area of the basin, such as TZ-23 and TZ-30, formed 293 Ma and 296 Ma respectively, indicating a pooling in the early Hercynian. The good correlation between the authigenic illite ages and the thickness of the bituminous sandstones suggests that the palaeotectonic framework be one of the main controlling factors and the ancient oil pools located in and around the depocenter, such as Qiao-1 and Kongque-1, be formed relatively early. The isotopic dating results are basically consistent with the results of conventional hydrocarbon accumulation history study and further highlight the differences in accumulation times between oil pools in different parts of the basin.