Stratigraphic attribution of 7590~8060 m sect of WT1 Well in northeastern Sichuan and its enlightenment to oil and gas exploration
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摘要:
WT1井完钻井深8060 m,刷新了中国石油陆上井深纪录。但其灯影组下伏地层归属问题一直悬而未决,前期由于油基泥浆的影响一直被认为是南华系。利用岩石学、碎屑锆石U-Pb年代学及地球化学方法,对该井7590~8060 m段地层进行对比研究。WT1井为泥岩、粉砂岩、砂岩夹白云岩组合,见硅质岩、磷块岩及硅磷质条带等夹层。碎屑锆石最年轻的年龄峰值分别为654.5±7.1 Ma、644±5 Ma。岩屑及岩石的化学蚀度指数(CIA)大于60。结果表明,WT1井7590~8060 m段地层岩石组合与区域上陡山沱组岩石组合极相似;其沉积时代应晚于644±5 Ma,且沉积时期的气候属温暖潮湿型。研究结果综合限定了WT1井灯影组之下7590~8060 m段应属震旦系陡山沱组,预示着川东北地区可能存在陡山沱期的裂谷,有利于打开川东北地区震旦系—下古生界的油气勘探局面。
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关键词:
- WT1井 /
- 油气勘探 /
- 碎屑锆石U-Pb年龄 /
- CIA /
- 川东北地区
Abstract:The completion depth of the WT1 Well is 8060 m, refreshing the onshore well depth record of CNPC.However, the attribution of the lower strata of the Dengying Formation has not been determined, and it has been considered to be the Nanhua System due to the influence of oil-base mud.Petrology, detrital zircon U-Pb chronology and geochemical methods were used to study the strata between 7590~8060 m in this well.The rocks include mudstone, siltstone, sandstone and dolomite, with intercalation of siliceous rocks, phosphorous rocks, siliceous and phosphorous bands.The youngest peak ages of detrital zircons are 654.5±7.1 Ma and 644±5 Ma respectively.The CIA(chemical index of alteration) value in cuttings and rocks is great than 60.The results show that the lithologic assemblage in 7590~8060 m sect of WT1 Well is very similar to that of the Doushantuo Formation in the region.The deposition age should be later than 644±5 Ma, and the climate during the deposition period was warm and humid.The research results show that 7590~8060 m sect below the Dengying Formation of Wutan 1 Well belongs to the Doushantuo Formation of Sinian System.This indicates that the existence of a rift developed in the period of Doushantuo, which is conducive to the mineralization of Sinian and Lower Paleozoic oil and gas in northeastern Sichuan.
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Key words:
- WT1 Well /
- oil and gas exploration /
- detrital zircon U-Pb chronology /
- CIA /
- northeastern Sichuan
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图 1 四川盆地及邻区构造单元分区图及WT1井位置图(据参考文献[3]修改)
Figure 1.
表 1 上地壳各类岩石、矿物CIA值[8]
Table 1. CIA values of various rocks and minerals in the upper crust
岩石 矿物 CIA值 气候和风化程度 平均上地壳 钠长石 50 反映寒冷干燥气候下低等风化程度 更新世冰碛岩基质 钙长石 50 更新世冰期粘土岩 钾长石 50~55 60~65 平均页岩 白云母 70~75 反映温暖湿润气候下中等风化程度 75 亚马逊泥岩 伊利石 75~85 反映炎热、潮湿的热带、亚热带气候下高等风化程度 蒙脱石 75~85 80~90 残留粘土 绿泥石 85~100 100 高岭石 100 注:CIA=Al2O3/(Al2O3+CaO*+Na2O)×100, CaO*指岩石中与硅酸盐相结合的CaO含量 表 2 WT1井7590~8060 m段取样井段的CIA值(部分)
Table 2. CIA value of 7590~8060 m sect in WT1 Well
% 取样深度/m Al2O3 K2O CaO Na2O CaO* CIA 取样深度/m Al2O3 K2O CaO Na2O CaO* CIA 7628 37.46 8.01 6.30 0.01 0.01 72.34 7973 37.49 5.07 6.61 0.65 0.65 75.23 7636 32.57 6.81 11.43 0.24 0.24 63.81 7974 36.28 4.97 8.32 0.33 0.33 72.71 7637 33.70 7.20 10.41 0.14 0.14 65.50 7975 36.50 4.94 8.39 0.48 0.48 72.55 7642 38.50 7.45 6.16 0.36 0.36 73.37 7976 36.26 4.98 8.32 0.58 0.58 72.31 7643 38.67 7.44 6.20 0.40 0.40 73.36 7977 36.11 4.98 8.28 0.44 0.44 72.49 7644 38.79 7.46 6.21 0.24 0.24 73.61 7978 26.06 1.84 10.46 1.38 1.38 65.58 7646 38.78 7.30 3.61 0.38 0.38 77.46 7979 25.89 1.84 10.48 1.44 1.44 65.29 7647 35.92 6.88 7.27 0.30 0.30 71.32 7980 25.99 1.84 10.52 1.14 1.14 65.81 7648 35.46 6.85 7.24 0.29 0.29 71.15 7981 25.99 1.85 10.46 1.18 1.18 65.83 7649 35.52 6.87 7.23 0.33 0.33 71.11 7982 31.01 3.41 9.59 0.91 0.91 69.03 7650 35.67 6.86 7.30 0.12 0.12 71.42 7983 30.79 3.41 9.71 0.85 0.85 68.78 7651 35.16 6.68 7.60 0.03 0.03 71.07 7984 33.47 3.76 7.58 0.93 0.93 73.17 7654 35.28 6.34 8.44 0.48 0.48 69.80 7985 33.18 3.78 7.57 1.01 1.01 72.86 7655 35.48 6.35 8.44 0.45 0.45 69.96 7986 33.32 3.78 7.52 0.85 0.85 73.29 7656 35.29 6.66 7.25 0.19 0.19 71.44 7987 31.77 2.75 7.11 1.35 1.35 73.92 7657 35.65 6.26 6.74 0.22 0.22 72.95 7988 31.44 2.76 7.12 1.23 1.23 73.89 7658 36.85 6.48 7.15 0.48 0.48 72.31 7989 32.80 3.21 6.90 1.05 1.05 74.63 7659 38.34 6.75 5.60 0.57 0.57 74.79 7990 32.94 3.22 6.89 1.37 1.37 74.17 7660 39.06 6.72 4.21 0.49 0.49 77.38 7991 32.81 3.21 6.94 1.29 1.29 74.15 7661 40.02 7.02 3.51 0.47 0.47 78.43 7992 36.62 5.00 6.77 0.52 0.52 74.88 7662 38.31 6.86 5.00 0.53 0.53 75.57 7993 36.55 5.00 6.73 0.20 0.20 75.39 7664 37.75 7.03 7.21 0.19 0.19 72.33 7994 36.47 5.01 6.78 0.45 0.45 74.88 7672 35.93 6.19 8.75 0.04 0.04 70.57 7995 36.41 5.02 6.77 0.42 0.42 74.87 7673 35.03 6.14 8.86 0.34 0.34 69.56 7996 36.03 4.80 6.33 0.42 0.42 75.73 7674 32.72 5.47 9.65 0.54 0.54 67.64 7997 36.06 4.80 6.31 0.73 0.73 75.29 7675 30.87 4.86 10.22 0.67 0.67 66.21 7998 35.92 4.81 6.44 0.39 0.39 75.53 7678 27.95 4.75 15.01 0.19 0.19 58.35 7999 28.08 3.04 14.68 1.12 1.12 59.85 7679 27.98 4.75 14.96 0.04 0.04 58.61 8000 34.50 4.15 6.08 1.13 1.13 75.24 7685 32.55 5.75 13.04 0.01 0.01 63.38 8001 25.74 3.11 12.59 0.11 0.11 61.96 7686 31.45 5.59 11.83 0.14 0.14 64.17 8002 32.89 4.32 9.67 0.70 0.70 69.11 7687 31.15 5.58 11.75 0.20 0.20 63.98 8003 32.72 3.71 9.89 0.95 0.95 69.23 7688 31.38 5.58 11.82 0.04 0.04 64.28 8004 37.11 4.93 4.10 0.69 0.69 79.25 7690 31.21 5.57 11.93 0.10 0.10 63.95 8005 36.95 4.70 5.31 0.78 0.78 77.40 7691 33.39 5.50 7.13 0.63 0.63 71.57 8006 34.37 4.46 6.01 0.61 0.61 75.63 7693 37.36 6.01 6.06 0.33 0.33 75.07 8007 36.08 4.37 6.41 1.09 1.09 75.24 7694 37.88 6.07 6.07 0.71 0.71 74.67 8008 27.75 2.15 11.05 2.12 2.12 64.44 7696 36.13 6.00 8.02 0.31 0.31 71.61 8009 35.57 4.80 7.74 0.58 0.58 73.05 7697 36.04 5.96 8.00 0.08 0.08 71.97 8010 33.97 4.76 8.65 0.55 0.55 70.88 7698 35.98 5.99 8.06 0.25 0.25 71.57 8011 36.59 5.09 6.86 0.70 0.70 74.31 7699 36.11 5.99 8.09 0.38 0.38 71.40 8012 30.52 2.48 6.98 2.07 2.07 72.58 7700 39.24 6.26 3.59 0.77 0.77 78.71 8013 23.09 1.54 9.29 1.10 1.10 65.93 7701 39.25 6.24 3.52 0.68 0.68 78.99 8014 27.29 1.85 9.50 2.02 2.02 67.13 7704 35.10 5.98 8.40 0.19 0.19 70.65 8015 18.25 2.47 19.68 0.10 0.10 45.06 7705 34.92 5.98 7.26 0.13 0.13 72.31 8016 32.28 4.16 8.41 0.79 0.79 70.71 7708 34.03 5.58 8.33 0.15 0.15 70.77 8017 37.15 5.20 4.91 0.88 0.88 77.17 7709 34.65 5.35 8.43 0.32 0.32 71.08 8018 28.60 3.69 13.54 0.40 0.40 61.86 7710 36.02 5.30 6.59 0.43 0.43 74.52 8019 28.66 3.70 13.53 0.68 0.68 61.54 7712 37.85 5.98 3.55 0.36 0.36 79.29 8020 28.82 3.69 13.52 0.52 0.52 61.91 7715 40.17 6.54 3.06 0.21 0.21 80.37 8021 27.64 1.46 9.01 2.31 2.31 68.39 7716 40.93 6.66 3.29 0.41 0.41 79.79 8022 30.93 3.81 11.17 0.63 0.63 66.47 7717 39.61 6.56 3.53 0.05 0.05 79.61 8023 31.56 4.09 12.16 0.77 0.77 64.96 7718 40.90 6.50 3.56 0.29 0.29 79.81 8024 28.79 3.60 13.42 0.53 0.53 62.14 7720 38.90 6.33 3.68 0.25 0.25 79.12 8025 32.81 4.72 10.54 0.32 0.32 67.80 7722 37.83 6.19 2.63 0.14 0.14 80.85 8030 38.33 5.65 5.59 0.62 0.62 76.37 7723 39.82 6.31 2.57 0.25 0.25 81.36 8031 38.47 5.66 5.60 0.64 0.64 76.37 7724 41.25 6.50 2.87 0.56 0.56 80.61 8032 34.67 3.50 7.68 2.17 2.17 72.20 7725 40.15 6.25 3.58 0.20 0.20 80.00 8033 34.45 3.50 7.69 2.21 2.21 72.00 7726 37.77 6.01 6.19 0.18 0.18 75.32 8034 37.86 5.65 7.23 0.26 0.26 74.25 7728 40.69 6.36 0.56 0.80 0.56 84.04 8035 36.46 5.39 8.44 0.29 0.29 72.08 7728.1 40.32 6.45 3.43 0.37 0.37 79.72 8036 34.80 4.77 8.75 0.30 0.30 71.57 7729 39.63 6.26 3.32 0.50 0.50 79.72 8037 37.94 5.49 6.84 0.42 0.42 74.85 7730 40.25 6.42 3.50 0.14 0.14 80.01 8038 38.88 5.73 4.36 0.19 0.19 79.09 7731 40.52 6.22 2.90 0.48 0.48 80.84 8039 40.37 5.82 3.60 0.41 0.41 80.41 7734 39.10 6.14 3.18 0.37 0.37 80.13 8040 40.45 5.96 3.75 0.28 0.28 80.18 7735 37.89 6.12 0.90 0.26 0.26 83.90 8042 37.03 4.17 3.86 0.94 0.94 80.50 7737 38.82 6.12 4.39 0.13 0.13 78.50 8043 43.08 4.98 0.94 1.15 0.94 85.92 -
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