Apatite fission track analysis of tectono-thermal history in the Xiushui area, southern Songliao Basin
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摘要: 【研究目的】松辽外围白垩世断陷盆地群在构造-热演化史的研究方面相对薄弱，秀水盆地作为松辽外围南部潜力较大的勘探新区，对盆地的热史-埋藏史的恢复已然成为该地区油气勘探亟待解决的重要问题。【研究方法】本文通过对秀水盆地辽法地1井5件钻井岩心样品开展磷灰石裂变径迹测试分析，首次厘定了盆地经历的热史-埋藏史及烃源岩成熟演化过程。【研究结果】结果表明，秀水盆地在早白垩世晚期地层达到最大埋深，而后持续抬升剥蚀近2000m；在初始沉降期大地热流值随时间线性升高，至120Ma左右达到最大值，约为100.5 mW/m2。而后经历了三段式降温过程，即先快速降温，再缓慢降温，最后快速降温的过程。该热流规律与邻区张强凹陷、松辽盆地相似并可对比。【结论】辽法地1井热史-埋藏史恢复结果表明，义县组三段烃源岩在90Ma左右进入到生油窗阶段，此后由于地层的抬升降温，热成熟度末进一步演化，从而最终定型。Abstract: [Objective] The tectono-thermal history of the Cretaceous fault basins in the Songliao peripheral area had not been well explored. The Xiushui basin is a new exploration area with high hydrocarbon potential in the southern part of the Songliao peripheral area. The reconstruction of the burial and thermal history of the Xiushui basin has become an important issue for hydrocarbon exploration in this area.[Methods] Based on five samples from the well LFD1 in the Xiushui Basin, burial and thermal history as well as hydrocarbon source rock evolution history of the Xiushui basin were studied using apatite fission track methods.[Results] The results show that the Xiushui basin reached its maximum burial depth in the late Early Cretaceous, and then uplift continued and denudated about 2000m. The terrestrial heat flow value increased linearly with time during the initial subsidence period, reaching the maximum value of about 100.5 mW/m2 at about 120Ma, and then experienced a three-stage cooling process, i.e., rapid cooling, then slow cooling, and finally rapid cooling. The heat flow pattern is similar to and comparable with the adjacent Zhangqiang Depression and the Songliao Basin.[Conclusions] The reconstruction results of the burial and thermal history of the well LFD1 indicate that the hydrocarbon source rocks of the third member of the Yixian Formation entered the oil generation window around 90 Ma, and thereafter, due to the uplift and cooling of the formation, the thermal evolution of the source rock ceased, thus remain unchanged to date.
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