川中高石梯—磨溪构造寒武系龙王庙组成藏地球化学研究

发布时间：2018-05-05 15:20

本文选题：四川盆地 + 高石梯-磨溪构造　；参考：《成都理工大学》2017年硕士论文

【摘要】：川中古隆起是一个继承性发育的大型加里东期剥蚀古隆起,古隆起东段高部位是天然气富集有利区,高石梯-磨溪构造便位于古隆起的东段。截至2013年底,高石梯一磨溪地区寒武系龙王庙组已探明天然气地质储量4404×10~8m~3。龙王庙组岩石类型主要为晶粒白云岩、残余砂屑白云岩、残余鲕粒白云岩等,储集空间类型为粒间晶间孔,部分为粒间晶间溶孔、粒内溶孔、铸模孔、生物潜穴/生物钻孔及溶缝。通过岩心观察、岩石薄片观察,认为高石梯—磨溪构造龙王庙组孔洞缝中矿物充填的世代关系为:晶粒状白云石→沥青→石英。对龙王庙组围岩及孔洞充填的白云石开展了锶、碳、氧同位素的分析,并对比了他们之间的差异性,认为围岩和晶洞充填的白云石的~(87)Sr/~(86)Sr比值均明显高于同期寒武纪海水的~(87)Sr/~(86)Sr比值,充填的白云石~(87)Sr/~(86)Sr比值和围岩没有明显的差异,这种富锶流体明显的改造了围岩,在孔洞中沉淀晶粒状的白云石。晶洞中充填的白云石δ~(13)C、δ~(18)O同位素和围岩的差值相对较小,但晶洞充填的白云石的δ~(18)O比围岩更偏负,表明充填的白云石可能是在相对更高的温度下沉淀的。对孔洞中充填的石英开展了硅、氧同位素和包裹体氢同位素的分析。研究认为,磨溪构造龙王庙组储层孔洞中充填的石英的流体源为成岩流体,和岩浆水及变质水等无关。石英矿物的~(87)Sr/~(86)Sr比值表明,沉淀石英的富硅质的地层水为外来的富锶流体,结合氢-氧同位素的特征认为这种富锶的硅质流体可能是由最初的大气淡水或与海水混合并封存演化而来的地层水。以孔洞中充填的矿物序列为主线,通过对包裹体岩相学、激光拉曼、均一温度等分析,认为川中高石梯-磨溪构造龙王庙组至少存在四期油气充注。不同期次流体包裹体的特征,表明了油藏流体由液态烃(古油藏)→液态烃+气态烃(古油气藏)→油裂解为天然气(古油气藏)→气态烃(天然气藏)的过程。通过包裹体均一温度及龙王庙组埋藏-热演化历史厘定了油气充注时间,并通过石英矿物包裹体的~(40)Ar—~(39)Ar定年分析,将龙王庙组天然气成藏的时间确定为125.80±8.20Ma。利用锶同位素地球化学数据以及现今地层压力的资料,建立了龙王庙组流体体系,认为龙王庙组天然气成藏期未表现出流体跨层流动的迹象,气藏具有优越的保存条件。
[Abstract]:The central Sichuan paleouplift is a large Caledonian denuded paleouplift which is inherited and developed. The upper part of the eastern part of the paleouplift is a favorable area for natural gas enrichment, and the Gaoshitian-Moxi structure is located in the eastern part of the paleouplift. By the end of 2013, the Cambrian Longwangmiao formation in the Gaoshitiyimoxi area had proved gas reserves of 4404 脳 10 ~ (8) mm ~ (3). The rock types of Longwangmiao formation are mainly grain dolomite, residual sand dolomite, residual oolitic dolomite, etc. The reservoir space type is intergranular pore, partly intergranular dissolved pore, intragranular dissolved pore, mold pore, etc. Biological submersible / biological drilling and dissolving. Based on core observation and thin slice observation, it is considered that the intergenerational relationship of mineral filling in the hole joint of the Longwangmiao formation of Gaosita-Moxi structure is: granular dolomite bitumen and quartz. The strontium, carbon and oxygen isotopes of dolomite filled with surrounding rocks and holes in Longwangmiao formation were analyzed, and their differences were compared. It is considered that the ratios of the rock rocks and the dolomite filled with crystal caverns are obviously higher than those of the Cambrian seawater during the same period, but there is no obvious difference between the ratio of 87 ~ (87) Sr ~ (- / -) ~ (86) Sr ~ + and the surrounding rock, and the strontium rich fluid has obviously modified the surrounding rock. A dolomite precipitated in a hole. The 未 ~ (13) C, 未 ~ (18) O isotopes of dolomite filled in crystal caverns are relatively small, but the 未 ~ (18) ~ (18) O value of dolomite filled with crystal caverns is more negative than that of surrounding rocks, indicating that the dolomite filled with dolomite may have precipitated at a relatively high temperature. Silicon, oxygen and inclusion hydrogen isotopes were analyzed in quartz filled with pores. It is considered that the fluid source of quartz filled in the hole of Longwangmiao formation in Moxi structure is diagenetic fluid, independent of magmatic water and metamorphic water. The Sr / P / 86 Sr ratio of quartz minerals indicates that the silicon-rich formation water precipitated by quartz is an extraneous strontium rich fluid. Combining the characteristics of hydrogen and oxygen isotopes, it is suggested that this strontium rich siliceous fluid may be the formation water derived from the initial atmospheric fresh water or mixed with seawater and sealed. Taking the mineral sequence filled in the pores as the main line and analyzing the petrography, laser Raman and homogenization temperature of the inclusions, it is concluded that there are at least four stages of oil and gas filling in the Longwangmiao formation of the Gaoshi-Moxi structure in the middle of Sichuan. The characteristics of fluid inclusions in different periods indicate the process of fluid cracking from liquid hydrocarbon (paleo-reservoir) / liquid hydrocarbon (paleo-hydrocarbon) to natural gas (paleo-reservoir) / gaseous hydrocarbon (natural gas reservoir). Based on the homogenization temperature of inclusions and the burial and thermal evolution history of Longwangmiao formation, the filling time of oil and gas is determined, and the time of gas accumulation in Longwangmiao formation is determined to be 125.80 卤8.20 Ma. The fluid system of Longwangmiao formation has been established by using strontium isotope geochemical data and the data of present formation pressure. It is considered that the gas reservoir of Longwangmiao formation did not show the sign of fluid flowing across layers during the reservoir forming period, and the gas reservoir has superior preservation conditions.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13

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