本文選題：白云巖　切入點(diǎn)：二疊系　出處：《成都理工大學(xué)》2016年博士論文

【摘要】：措勤盆地自古生界至白堊紀(jì)發(fā)育巨厚的海相碳酸鹽巖和碎屑巖沉積,是青藏高原第二大海相沉積盆地。志留系扎弄俄瑪組以及二疊系木糾錯(cuò)組砂糖狀白云巖油苗的發(fā)現(xiàn)證實(shí)這一地區(qū)古生界存在油氣運(yùn)移和聚集的過程,具備良好的油氣勘探前景。論文通過前人資料收集、野外地質(zhì)調(diào)查及室內(nèi)測(cè)試分析,對(duì)措勤盆地古生代晶粒狀白云巖進(jìn)行了詳細(xì)研究。首先通過顯微觀察,將白云石劃分為A型(它形)、S型(半自形)以及E型(自形)。進(jìn)而根據(jù)環(huán)帶結(jié)構(gòu)劃分為單環(huán)帶和多環(huán)帶白云石,其中單環(huán)帶白云石包括霧心亮邊及亮心霧邊兩種類型。采用陰極發(fā)光及顯微熒光詳細(xì)研究了S型霧心亮邊白云石、S型亮心霧邊白云石、E型多環(huán)帶白云石以及E型鞍狀白云石的發(fā)光特征。結(jié)果顯示霧心亮邊白云石熒光識(shí)別精度高于陰極發(fā)光,部分晶體可以觀察到多個(gè)熒光環(huán)帶。電子探針分析表明,白云石核心一般SrO含量相對(duì)較高,FeO和MnO含量低。多環(huán)帶及鞍狀白云石具有極高的FeO含量,且高值均集中在內(nèi)環(huán)帶。環(huán)帶白云石由邊緣向核心Mg/Ca比值普遍具有高低波動(dòng)的特征,鞍狀白云石邊緣Mg/Ca比值高于核心。白云石包裹體均一溫度主要分布于120~180℃之間,鹽度均值遠(yuǎn)高于現(xiàn)代海水鹽度,白云巖的形成經(jīng)歷了高溫高鹽度的演化過程。微區(qū)同位素測(cè)試結(jié)果顯示單環(huán)帶白云石δ13C值介于-0.18~+0.40‰,δ18O值-2.30~-4.46‰;多環(huán)帶白云石δ13C值介于-0.22~-2.38‰,δ18O值-2.58~-7.75‰。通過氧同位素分餾方程計(jì)算得到白云石化流體的δ18OSMOW值介于+6~+16‰,形成單環(huán)帶白云石的流體來自原始沉積海水的蒸發(fā)殘余或與地下鹵水的混合,多環(huán)帶白云石δ18OSMOW值偏低,可能受到深部熱液的改造或地下淡水的補(bǔ)給。白云巖經(jīng)歷了兩期白云石化作用:第一期為回流滲透白云石化作用,海水通過粒間孔或晶間孔滲透到碳酸鈣沉積物或石灰?guī)r地層,在成巖過程中通過離子置換形成第一世代微—粉為主的白云石。第二期埋藏白云石化作用占主導(dǎo),形成以粉—細(xì)晶為主,具有霧心亮邊和亮心霧邊結(jié)構(gòu)的第二世代白云石,同時(shí)在流體作用較強(qiáng)的部位沉淀多環(huán)帶結(jié)構(gòu)的第三世代白云石。儲(chǔ)集性研究表明,白云巖儲(chǔ)層非均質(zhì)性強(qiáng),溶蝕孔洞和裂縫發(fā)育,可劃歸裂縫—溶蝕孔隙型儲(chǔ)層體系。建設(shè)性成巖作用主要包括白云石化作用、溶蝕作用以及破裂作用。白云巖中發(fā)育兩期油氣包裹體,第一期主要分布于方解石脈中,以液態(tài)烴包裹體為主,與其伴生的含烴鹽水包裹體平均均一溫度130.8℃。第二期主要分布于白云石中,以氣態(tài)烴包裹體為主,與其伴生的含烴鹽水包裹體平均均一溫度148.2℃。大規(guī)模油氣充注發(fā)生在埋藏白云石化作用之后,木糾錯(cuò)組含油白云巖可能屬于“新生古儲(chǔ)”型油氣藏。
[Abstract]:From Paleozoic to Cretaceous, the Cooqin Basin is the second largest marine sedimentary basin in Qinghai-Xizang Plateau.The discovery of granulated dolomite oil seedlings in Zhanomar formation of Silurian system and the error-correcting group of Permian shows that there is a process of hydrocarbon migration and accumulation in the Paleozoic in this area, which has a good prospect for oil and gas exploration.Based on the previous data collection, field geological investigation and laboratory test and analysis, the Paleozoic granular dolomite in Cuoqin Basin is studied in detail.Firstly, dolomite is divided into A type (S type) and E type (E type) by microscopic observation.According to the structure of the annular zone, dolomite can be divided into single-ring zone and multi-ring zone dolomite, in which the single-ring dolomite includes two types: bright edge of fog center and bright mist edge of bright core.The luminescence characteristics of S type fog core bright edge dolomite, S type bright core mist edge dolomite E type multi ring dolomite and E type saddle dolomite were studied in detail by cathodic luminescence and microfluorescence.The results show that the fluorescence recognition accuracy of dolomite with bright edge is higher than that of cathodoluminescence, and several fluorescence bands can be observed in some crystals.Electron probe analysis shows that the general SrO content of dolomite core is relatively high, and the content of Feo and MnO is relatively low.The polycyclic zone and saddle dolomite have extremely high FeO content and the high values are concentrated in the inner ring zone.The Mg/Ca ratio of dolomite from edge to core generally fluctuates in the annular zone, and the Mg/Ca ratio at the edge of saddle dolomite is higher than that in core.The homogeneous temperature of dolomite inclusions is mainly distributed between 120 鈩，

本文編號(hào)：1721728