柴达木盆地三湖地区第四系气藏形成与“烟囱效应”
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摘要
高分辨率地震资料表明,柴达木盆地三湖地区第四系气藏周围发育有气烟囱。第四系具有较高的地温梯度,深部发育了低幅超压;甘森泉-小柴旦基底断裂影响气藏构造的完整性;第四系饱含高矿化度地层水泥岩构成的盖层可以起到一定的封盖作用。这些因素相互作用,最终导致了气烟囱的形成。气烟囱的发育可以解释第四系天然气组分、重烃碳同位素等体现出来的混源特征,解决第四系各层序源岩生烃潜力和含气储量之间存在的矛盾。总之,气烟囱作为天然气的垂向运移通道对该区第四系气藏的成藏起到重要作用。
The high resolution seismic data show that gas chimneys exist around Quaternary gas reservoirs in Sanhu area of Qaidam basin. The Quaternary system is characterized by high geothermal gradient, with low scope of overpressure in its deep and shale caprock saturated with formation water of high salinity. The Gansenquan-Xiaochaidan basement faults affect the integrality of gas reservoir structures. These interacted factors result in the formation of gas chimney. The existence of gas chimney can explain the mixed source characters of Quaternary gas composition and ethane carbon isotope, thus resolving the contradictions between source rock hydrocarbon-generating potentials and gas reserves of each sequence. In conclusion, the gas chimney as a vertical path of natural gas migration plays an important role in Quaternary gas accumulation in this area.
The high resolution seismic data show that gas chimneys exist around Quaternary gas reservoirs in Sanhu area of Qaidam basin. The Quaternary system is characterized by high geothermal gradient, with low scope of overpressure in its deep and shale caprock saturated with formation water of high salinity. The Gansenquan-Xiaochaidan basement faults affect the integrality of gas reservoir structures. These interacted factors result in the formation of gas chimney. The existence of gas chimney can explain the mixed source characters of Quaternary gas composition and ethane carbon isotope, thus resolving the contradictions between source rock hydrocarbon-generating potentials and gas reserves of each sequence. In conclusion, the gas chimney as a vertical path of natural gas migration plays an important role in Quaternary gas accumulation in this area.
引文
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[9]王子明,阮家聚,魏国显,等.柴达木盆地东部高分辨率地震勘探应用研究与效果[J].石油地球物理勘探,2002,37(6):569-577.
[2]Heggland Meldahl R P,Groot P.Chimneys in the Gulf of Mexico[J].The American Oil and Gas Reporter,2000.78-83.
[3]Heggland.Detection of gas migration from a deep source bythe use of exploration3D seismic data[J].Marine Geology,1997,137:41-47.
[4]解习农,刘晓峰,赵士宝,等.异常压力环境下流体活动及其油气运移主通道分析[J].地球科学,2004,29(5):589-595.
[5]顾树松.柴达木盆地东部第四系气田形成条件及勘探实践[M].北京:石油工业出版社,1993.
[6]李明宅,张洪年,刘华,等.生物气模拟实验的进展[J].石油与天然气地质,1996,17(2):117-122.
[7]汤良杰,金之钧,戴俊生,等.柴达木盆地及相邻造山带区域断裂系统[J].地球科学,2002,27(6):676-682.
[8]王明明,李本亮,魏国齐,等.柴达木盆地东部第四纪水文地质条件与生物气成藏[J].石油与天然气地质,2003,24(4):341-345.
[9]王子明,阮家聚,魏国显,等.柴达木盆地东部高分辨率地震勘探应用研究与效果[J].石油地球物理勘探,2002,37(6):569-577.
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