Fluid charging history in Ledong 10 area, Yinggehai Basin, revealed by CO2 inclusion characteristics
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摘要: 莺歌海盆地新生界富含天然气,近年来在盆地中深层勘探取得了突破;而乐东10区气田的发现,引起了对非底辟构造的中深层岩性气藏天然气运移成藏问题的关注。乐东10区块中新统黄流组天然气藏富含CO2,为了查明CO2在天然气藏中的运移特征和期次,以包裹体岩相学为前提,结合激光拉曼光谱分析对其进行了研究。该区包裹体主要包括盐水包裹体、二氧化碳包裹体、气相甲烷包裹体、混合气包裹体、含混合气的盐水溶液包裹体五种类型。使用激光拉曼分析和显微测温技术,定量分析了CO2包裹体的均一温度和密度等参数;结合CO2流体包裹体捕获条件、沉积特征、埋藏史以及CO2同位素值,认为该区CO2为两期幕式充注:第一期为1.4~0.9 Ma充注的高密度无机成因CO2;第二期为0.7~0.4 Ma充注的中密度无机成因CO2。Abstract: The Cenozoic strata of Yinggehai Basin is rich in natural gas, and exploration breakthroughs have been achieved in the middle and deep strata of the basin in recent years. The discovery of gas fields in the Ledong 10 area had attracted concerning for the migration and accumulation of natural gas in lithologic reservoirs in the middle and deep strata of nondiapir structures. The natural gas reservoir in the Miocene Huangliu Formation in the Ledong 10 block appeared to have a high content of CO2. The characteristics and periods of CO2 migration to natural gas reservoirs were discussed by the approaches including Laser Raman spectroscopy and combined with inclusion petrographic observation. Five types of fluid inclusions were classified, including brine inclusions, CO2 inclusions, gas-phase CH4 inclusions, gas-mixed inclusions and gas-mixed brine inclusions. According to the homogenization temperature and density of CO2 inclusions measured by Laser Raman and microthermometry analysis, and combined with the estimation of the capture conditions of CO2 inclusions, sedimentary characteristics, burial history as well as isotopic composition of CO2, two-stage filling mode for CO2 gas reservoirs was then concluded. The first stage was high-density inorganic-origin CO2 charged between 1.4-0.9 Ma; the second stage was medium-density inorganic CO2 charged between 0.7-0.4 Ma.
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Key words:
- CO2 inclusion /
- Laser Raman analysis /
- filling period /
- Cenozoic /
- Ledong 10 area /
- Yinggehai Basin
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图 9 莺歌海盆地乐东10区油气运聚成藏模式
据杨计海等[2],有修改。
Figure 9. Model showing oil and gas migration and accumulation in Ledong 10 area, Yinggehai Basin
表 1 莺歌海盆地乐东10区构造流体包裹体分类特征
Table 1. Classification characteristics of fluid inclusions, Ledong 10 area, Yinggehai Basin
分类特征 赋存矿物 形态大小 颜色 拉曼成分 相态(单相、两相、三相) 相比例(两相、多相) 成因类型 产状(分布特征) 石英 方解石,长石 偏光特征 荧光特征(蓝光) 盐水包裹体 常见 少见 近圆形,椭圆形,近椭圆形,3~14 μm,主要分布于10 μm 无色 无 无 两相为主 气相2%~15% 成岩、成藏过程中有关的流体包裹体(次生包裹体) 愈合裂隙,其次为单个分布 二氧化碳包裹体 常见 少见 近圆形,椭圆形,近椭圆形,2~12 μm 盐水相无色;液态气无色;气相为黑色或灰黑色 无 CO2、H2O 单一气相、气—液两相、气—液—盐水三相 单一气相为70%以上;气—液两相为60%和40%,气—液—盐水三相为50%,35%,15% 混合气包裹体 少见 有,难观察 近圆形,椭圆形,近椭圆形,5~13 μm 黑色 无 CH4、N2、CO2 气相为主 气相70%以上 气相甲烷包裹体 可见 有,难观察 形态多变,呈圆形、椭圆形,3~8 μm 黑色或者灰黑色 无 CH4 单一气相 气相70%以上 油气成藏过程中有关的流体包裹体(次生包裹体) 含混合成分的盐水包裹体 少见 有,难观察 形态多变,近椭圆形,不规则形态,比较常见,2~10 μm 液相呈褐黄色,气相呈黑色 浅黄色、黄色 CH4、N2、H2O 气—液两相或气相的液体包裹体 气相2%~15% 表 2 莺歌海盆地乐东10区二氧化碳包裹体拉曼定量分析数据
Table 2. Raman quantitative data of CO2-H2O inclusions, Ledong 10 area, Yinggehai Basin
序号 井号 层位 深度/m 费米双峰间距/cm-1 密度/(g·cm-3) 同期盐水包裹体均一温度/℃ 包裹体岩石学特征 1 L1-13 黄流组 4 169.65 104.55 0.81 155.0 石英愈合裂缝 2 L1-13 黄流组 4 172.04 104.53 0.79 171.0 石英愈合裂缝 3 L1-13 黄流组 4 172.04 104.44 0.76 170.0 石英愈合裂缝 4 L1-13 黄流组 4 172.04 104.65 0.84 161.5 石英愈合裂缝 5 L1-13 黄流组 4 172.04 104.77 0.87 151.5 石英愈合裂缝 6 L1-13 黄流组 4 172.04 104.75 0.88 151.0 石英愈合裂缝 7 L1-13 黄流组 4 172.04 104.68 0.85 165.5 石英愈合裂缝 8 L1-13 黄流组 4 174.16 103.77 0.47 178.0 石英愈合裂缝 9 L1-13 黄流组 4 221.00 103.75 0.46 175.0 石英愈合裂缝 10 L1-13 黄流组 4 221.00 104.77 0.88 150.0 石英愈合裂缝 11 L1-13 黄流组 4 262.00 104.75 0.87 163.0 石英愈合裂缝 12 L1-13 黄流组 4 301.00 103.68 0.43 177.0 石英愈合裂缝 13 L1-13 黄流组 4 301.00 104.67 0.85 160.0 石英愈合裂缝 14 L1-6 黄流组 4 189.90 104.54 0.80 160.5 石英愈合裂缝 15 L1-12 梅山组 4 238.00 104.77 0.89 150.5 石英愈合裂缝 16 L1-12 梅山组 4 350.00 104.73 0.87 159.0 石英愈合裂缝 17 L1-12 梅山组 4 372.00 103.79 0.48 173.0 石英愈合裂缝 18 L1-12 梅山组 4 412.00 104.66 0.85 161.5 石英愈合裂缝 19 L2-1 梅山组 3 900.00 104.79 0.89 156.0 石英愈合裂缝 20 L2-1 梅山组 4 106.20 103.91 0.53 174.0 石英愈合裂缝 21 L2-1 梅山组 4 106.20 104.57 0.81 154.0 石英愈合裂缝 -
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