黔桂地区古生界储层流体与成藏成矿的关系研究

【作者】 徐仕海；

【导师】 顾雪祥；

【作者基本信息】 成都理工大学 ， 矿物学、岩石学、矿床学， 2007， 博士

【摘要】 本文在大量野外观测的基础上，以流体包裹体技术方法为主要研究手段，系统研究了黔桂地区古生界储层流体与油气成藏和金属成矿的关系，结果表明：研究区古油藏和金属矿床中的流体包裹体，大小悬殊，形态多样，除液相水包裹体和气液水包裹体普遍存在外，油气藏中以CH₄包裹体和CH₄-H₂O包裹体为主；金矿床中则以CO₂包裹体和CO₂-H₂O包裹体为主。本区二叠系礁灰岩型古油藏中，气液水包裹体均一温度主要集中于90～160℃之间，而滇黔桂地区微细浸染型金矿床成矿流体的均一温度多为150～250℃，明显高于古油藏的形成温度。油气储层流体的盐度一般在5 wt NaCl％以下，而金矿成矿流体盐度主要为3.5～8.4 wt NaCl％，明显高于前者。成藏流体的压力值变化于42×10⁵～654×10⁵Pa之间。单个包裹体显微激光拉曼光谱分析表明，古油藏流体包裹体成分主要为CH₄，次为CO₂；金属矿床以CO₂为主，含有少量的N₂和CH₄。二叠系生物礁古油藏中溶孔、裂缝充填的三期方解石，第一期均一温度77～84℃，以液相水包裹体和气液水包裹体为主，偶见有机质包裹体；第二期均一温度91～103℃，主要为C₂H₆液相有机质包裹体，次为CH₄气相有机质包裹体、沥青包裹体和气液水包裹体；第三期均—温度117～155℃，为大量气相有机质包裹体，即随着温度的增高，有机质成熟度加大，包裹体成分由以液态烃类为主，逐渐向气态烃类转变。烃类三期注入的时间分别为235～237.5 Ma、230～232.5Ma和227.5～185 Ma。利用流体包裹体资料，计算获得秧坝地区二叠纪～三叠纪古地温梯度为4.30～4.35℃／100m，平均为4.33℃／100 m；秧1井二叠系地层古埋藏深度为2564～3187m。二叠系地层剥露区的剥蚀量为2069～4606m。根据系统的流体包裹体研究资料，系统绘制了本区二叠系储层的热晕图、盐晕图、气晕图和流体势图。研究表明，二叠系储层流体运移的总体趋势是自南向北，并在册亨、望谟一带汇聚；结合油气保存的盖层条件，认为板街、秧坝、花冗、乐元一带为最有利的成藏远景区。通过系统综合研究，探讨了油气与金属成矿流体的起源、演化和成藏-成矿作用，揭示了油气成藏与金属成矿的内在联系，建立了研究区的成藏-成矿模式。更多还原

【Abstract】 Based on field observation, the fluid inclusion technique has been used to study the Paleozoic reservoir fluid and its relationship to hydrocarbon accumulation and ore mineralization in the Nanpanjiang-Youjiang regions, South China.Fluid inclusions in the paleo-oil reservoirs and the gold deposits in the studied area vary greatly both in size and in form. In addition to abundant liquid H₂O and liquid-vapor H₂O inclusions, CH₄ and CH₄-H₂O inclusions are dominated in the paleo-oil reservoirs, while CO₂ and CO₂-H₂O inclusions occur mainly in the gold deposits.In the Permian reef limestone reservoirs, homogenous temperatures of aqueous inclusions range from 90℃to 160℃, the salinity of the fluid is typically below 5 wt NaC1％. Homogenous temperatures and salinity of aqueous fluids in the sedimentary rock-hosted disseminated gold deposits are generally higher than those in paleo-oil reservoirs, typically varying from 150℃to 250℃and from 3.5 to 8.4 wt NaC1％, respectively. Pressure of the reservoir fluid varies from 42×10⁵ to 654×10⁵ Pa. Laser Raman microspectrometry analyses on single fluid inclusions indicate that the vapor phases of hydrocarbon inclusions in the paleo-oil reservoirs are dominated by CH₄ and subordinately CO₂, while the vapor components of fluid inclusions in the gold deposits are mainly CO₂, with minor amounts of N₂ and CH₄.There are three stages of solution pore-and fracture-filling calcite in the Permian reef paleo-oil reservoirs. Liquid H₂O and liquid-vapor H₂O inclusions with homogenization temperatures between 77-84℃are dominated in the first stage calcite, although hydrocarbon inclusions are occasionally also seen. Fluid inclusions in the second stage calcite are predominantly liquid C₂H₆ inclusions and subordinately vapor CH₄ inclusions, bitumen inclusions, and aqueous inclusions. Homogenization temperatures of the aqueous inclusions vary from 91℃to 103℃. The third stage calcite is characterized by abundant vapor hydrocarbon inclusions with homogenization temperatures between 117-155℃. It is thus indicated that with increased burial temperature and maturity of organic matter the major components of organic inclusions vary gradually from liquid hydrocarbons to vapor hydrocarbons. Hydrocarbon filling time of the corresponding three stages is estimated to be 235-237.5 Ma, 230-232.5 Ma, and 227.5-185 Ma, respectively.Based on fluid inclusion data, the paleogeothermal gradient during Permian and Triassic is calculated to be 4.30-4.35℃/100 m in the Yangba area, with an average of 4.33℃/100 m. The burial depth of Permian strata in the Well Yang-1 is estimated to be 2564-3187 m, and the denudation thickness of the Permian stratigraphy is estimated to be 2069-4606 m.Figures of temperature, salinity, CH₄ molar percentage and fluid potential contours of the Permian reservoirs in the study area show that the hydrocarbon reservoir fluid migrated in general from south to north and accumulated in the Ceheng and Wangmo areas. Coupled with the cap rock conditions for hydrocarbon conservation, it is suggested that the most favorable prospect area for hydrocarbon reservoirs is in Banjie, Yangba, Huarong and Leyuan.The origin and evolution of hydrocarbon and ore-forming fluids as well as their relationship to petroleum accumulation and ore mineralization were discussed. A model for reservoir formation and ore mineralization was established based on systematic and comprehensive investigation.更多还原