松遼盆地南部長(zhǎng)嶺凹陷—華字井階地含片鈉鋁石砂巖成巖流體演化

1、松遼盆地南部長(zhǎng)嶺凹陷華字井階地含片鈉鋁石砂巖成巖流體演化        本文以片鈉鋁石和含片鈉鋁石砂巖為研究對(duì)象,通過(guò)巖石學(xué)、穩(wěn)定同位素地球化學(xué)與流體包裹體地質(zhì)學(xué)等多學(xué)科相結(jié)合的綜合研究方法,開(kāi)展了松遼盆地南部長(zhǎng)嶺凹陷-華字井階地含片鈉鋁石砂巖的成巖流體演化研究。含片鈉鋁石砂巖的成巖共生序列為:伊蒙混層、方解石、自生高嶺石、次生加大石英、伊利石、片鈉鋁石和鐵白云石,CO2注入之后形成了片鈉鋁石和鐵白云石組合。通過(guò)片鈉鋁石的碳、氧同位素特征研究,結(jié)合松南中淺層CO2氣成因與分布,確定形成片鈉鋁石的CO2和氣藏中的CO

2、2具有相同的碳來(lái)源,絕大部分屬于幔源-巖漿型CO2。運(yùn)用伊利石K-Ar同位素測(cè)年、包裹體均一溫度和埋藏史-熱史曲線等方法,推斷出CO2充注時(shí)間為58.837Ma。根據(jù)火山噴發(fā)活動(dòng)時(shí)間、物質(zhì)成分等條件分析研究,證實(shí)了雙遼火山群活動(dòng)和同期的熱流底辟體上侵為松遼盆地南部長(zhǎng)嶺凹陷-華字井階地形成片鈉鋁石的CO2的主要來(lái)源。最后,總結(jié)出松遼盆地南部長(zhǎng)嶺凹陷-華字井階地含片鈉鋁石砂巖的成巖流體的演化過(guò)程Abundant of CO2 occurred in southern part of Songliao Basin, and as reported, most of the CO2 gas reser

3、voirs distributed in Qianan, Gudian and so on. As an active gas, CO2 can dissolve into water and form the acid fluid. Theoretically, ankerite, siderite and dawsonite can all become the effective products with the function of CO2-H2O-sandstone interaction, but recently, geological observation, synthe

4、tic experiment and numerical simulation are inclined to that dawsonite would make more sense. Numerous evidences show that, in the background with CO2 gas reservoir, as the trace mineral, dawsonite can make record on the migration, accumulation and seepage of CO2.Nowadays, abundant of dawsonite was

5、found in Changling Depression- Huazijing Step, southern part of Songliao Basin, which producing an ideal natural laboratory for doing research on fluid evolution in daswonite-bearing sandstone. Combining with petrology, stable isotopic analysis and fluid inclusion methods, the petrologic characteris

6、tic and genesis of CO2 for forming the dawsonite are studied; then we focus on the coupling relationship among volcanic activity, CO2 fluid and diagenesis of sandstone in the material contents and time scales; at last the evolution of diagenetic fluid in dawsonite-bearing sandstone is investigated.T

7、he diagenesis sequence for dawsonite-bearing sandstone in research area are as follows: illite and smectite mixed layer, micrite calcite, authigenic kaolinite, quartz overgrowth, late calcite, illite, dawsonite and ankerite. Among them, dawsonite and ankerite are the authigenic mineral combination w

8、hich formed after CO2 injection. In the late CO2 injection period, the weak acid fluid turns to be alkaline, and if the pressure of CO2 in porosity is higher, dawsonite formed, otherwise, the authigenic mineral is ankerite. These specific mineral combinations can keep track for transformation, aggre

9、ssion and seepage of CO2, so they can make contribute to the research on CO2 gas reservoir.Dawsonite13C values are -5.31.13, and the calculated values of CO2 gas in isotopic equilibrium with dawsonite are -4.55-11.72, meanwhile,13C values of the accompanying CO2 in Qianan and Honggang are -5.32-6.76

10、, so these calculated data is coincided with the values of free gas. Moreover, these data appears as an inorganic CO2 source, especially in the range for mantle- magmatic CO2 (-8-2). The ratios of 3He/4He(R) of natural gas samples range from (3.16±0.09)×10-6 to (6.94±0.20)×10-6,w

11、ith the R/Ra of 2.264.96, showing a mantle source characteristics. Combining with the truth that there is a good relationship between dawsonite-bearing sandstone and CO2, and both of them are controlled by basement faults, a same carbon source for forming dawsonite and free gas phase CO2 in middle-s

12、hallow layers can be suggested, and this kind of carbon source seems to belong to mantle-magmatic origin mixing with some organic CO2.Sequencing and timing are two new methods can be used to estimate the infilling time of CO2 which forming the dawsonite in Changling depression- Huazijing step.Throug

13、h fluid inclusions and diagenesis sequence studies, two terms of oil&gas infilling were determined, and dawsonite was found developing between these two infilling stages. The analysis of isotopic dating of autogenetic illite shows that the time for hydrocarbon injection is 92.558.8Ma, which is c

14、oincide with the first phase inclusions (developing in quartz overgrowth). The other stage of inclusions mainly developed in calcite cements, microfissure which cutting quartz debris and overthgrowths. Through homogenization temperature and buried&thermal history studies, the second phase of hyd

15、rocarbon injection was calculated to be between 37 and 20Ma. Then the filling time for CO2 which inducing the dawsonite genesis can be fixed to be 58.837Ma. After a series of research on the volcanic activities after late cretaceous, it is found that there is a great time coincidence among Shuanglia

16、o volcanic activity, inorganic CO2 infilling and genesis of dawsonite. The fluid inclusions data showed that abundant of CO2-melt inclusions were caught in alkaline olivine basalt by both phenocryst and xenoliths, Shuangliao volcanic cluster. Therefore, through the analysis on activities time and ma

17、terials of the volcano, the volcanic groups in Shuangliao and the intrusion of heat flow diaper bodies are confirm to play the predominant roles on the CO2 source for forming dawsonite.The fluid evolution can be divided into three stages: pre-CO2 (illite&smectite mixed layer and micrite calcite

18、step, kaolinite and quartz overgrowth step, late calcite and illite step ), dual infilling by CO2 & hydrocarbon and nowadays fluid. Once the formation water injected into CO2, its geochemical content would be change, such as appearing as high salinity and rich in Na+ and HCO3-. So the whole evol

19、ution in Changling depression- Huazijing step is a complex process accompanying continuous fluid infilling. The occurrence of dawsonite can be divided into two types, continuing growth and termination, depending on whether there is aqueous fluid in dawsonite-bearing areas. The former type means that under the dawsonite accompanying