0 引言
1 寒武系页岩气的地球化学特征
表1 中国南方寒武系筇竹寺组(牛蹄塘组、水井沱组)页岩气地球化学特征Table 1 The geochemistry of shale gas from Qiongzhusi(Niutitang or Shuijingtuo) Formation shales of Cambrian in South China |
地 区 | 层 位 | 井号 | 深度/m | 气体类型 | 样品编号 | 气体成分/% | 湿度 | 碳同位素/‰ | 氢同位素/‰ | δ15N2 /‰ | 资料来源 | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
C1 | C2 | C3 | CO2 | N2 | C1 | C2 | C3 | CO2 | C1 | C2 | |||||||||
威远 | 筇竹寺组 | 威201 | 1 520~1 523 | 天 然 气 | 98.32 | 0.46 | 0.01 | 0.36 | 0.81 | 0.48 | -36.9 | -37.9 | -140 | 吴伟等[6] | |||||
威201* | 1 520~1 523 | 99.09 | 0.48 | 0.42 | 0.00 | 0.48 | -37.3 | -38.2 | -0.2 | -136 | |||||||||
威201-H1 | 2 840 | 95.52 | 0.32 | 0.01 | 1.07 | 2.95 | 0.34 | -35.1 | -38.7 | -144 | |||||||||
威201-H1* | 2 840 | 98.56 | 0.37 | 1.06 | 0.43 | 0.37 | -35.4 | -37.9 | -1.5 | -138 | |||||||||
威201-H3 | 3 647 | 96.52 | 0.35 | 1.24 | 1.75 | 0.36 | -35.4 | -40.8 | -145 | ||||||||||
威201-H3* | 3 647 | 98.53 | 0.35 | 1.11 | 0.08 | 0.35 | -35.6 | -39.4 | |||||||||||
威202 | 2 595 | 99.27 | 0.68 | 0.02 | 0.02 | 0.01 | 0.70 | -36.9 | -42.8 | -43.5 | -2.2 | -144 | -164.0 | ||||||
威203* | 3 137~3 161 | 98.27 | 0.57 | 1.05 | 0.08 | 0.58 | -35.7 | -40.4 | -1.2 | -147 | |||||||||
鄂西北 | 水井沱组 | 宜页1井 | 1 894~2 113 | 天 然 气 | G1 | 91.17 | 0.94 | 0.03 | 0.70 | 6.90 | 1.05 | -33.1 | -38.1 | -38.9 | -16.8 | -134 | -146.1 | 罗胜元等[7].G1-G3为2017年5月14日取气;G4-G6为2017年5月25日取气;QJ-024-036为2017年5月28日取气;QJ-051取气2017年6月28日 | |
G2 | 90.60 | 0.94 | 0.03 | 1.12 | 7.13 | 1.06 | -33.3 | -38.3 | -38.8 | -15.5 | -131 | -153.7 | |||||||
G3 | 87.17 | 0.87 | 0.03 | 2.25 | 9.36 | 1.02 | -33.3 | -37.3 | -38.5 | -15.4 | -129 | -148.7 | |||||||
G4 | 90.52 | 0.86 | 0.02 | 0.90 | 7.43 | 0.96 | -33.6 | -38.1 | -38.7 | -16.2 | -129 | -168.0 | |||||||
G5 | 90.78 | 0.86 | 0.02 | 0.96 | 7.31 | 0.96 | -33.8 | -39.2 | -39.4 | -14.8 | -129 | -149.5 | |||||||
G6 | 89.61 | 0.86 | 0.02 | 1.27 | 8.13 | 0.97 | -33.8 | -36.0 | -38.7 | -14.6 | -129 | -152.9 | |||||||
QJ-024 | 88.02 | 0.83 | 0.02 | 0.85 | 9.37 | 0.96 | |||||||||||||
QJ-036 | 89.23 | 0.88 | 0.03 | 0.80 | 8.11 | 1.01 | |||||||||||||
QJ-051 | 92.75 | 0.89 | 0.04 | 0.05 | 5.86 | 0.99 | |||||||||||||
鄂西北 | 水井沱组 | 宜页1井 | 1 809.73 | 解 析 气 | CY-17 | 86.59 | 0.78 | 1.68 | 10.95 | 0.89 | -34.9 | -39.3 | -21.3 | 罗胜元等[7]; 何陈诚等[21] | |||||
1 826.73 | CY-24 | 87.70 | 1.40 | 0.63 | 10.27 | 1.57 | -33.8 | -40.0 | -21.8 | ||||||||||
1 843.20 | CY-32 | 85.06 | 1.29 | 0.94 | 12.71 | 1.49 | -34.8 | -41.0 | -21.6 | ||||||||||
1 854.34 | CY-38 | 89.01 | 3.00 | 0.58 | 7.41 | 3.26 | -33.0 | -41.1 | -22.2 | ||||||||||
1 858.72 | CY-40 | 81.90 | 2.92 | 0.64 | 14.54 | 3.44 | -33.2 | -41.3 | -20.7 | ||||||||||
1 870.84 | CY-46 | 95.48 | 3.95 | 0.57 | 0.00 | 3.97 | -34.2 | -40.9 | -21.7 | ||||||||||
鄂西北 | 牛蹄塘组 | 秭地1井 | 263.4 | 解 析 气 | 秭地1-1 | 27.53 | 2.25 | 70.34 | 0.00 | -28.8 | -12.5 | -202 | 5.7 | LIU等[22] | |||||
265.9 | 秭地1-2 | 61.02 | 1.80 | 37.19 | 0.00 | -30.2 | -10.2 | -196 | 5.2 | ||||||||||
268.6 | 秭地1-3 | 58.42 | 2.81 | 38.77 | 0.00 | -29.4 | -11.7 | -198 | 4.6 | ||||||||||
271.2 | 秭地1-4 | 16.02 | 4.96 | 79.03 | 0.00 | -29.9 | -12.8 | -207 | 6.8 | ||||||||||
275.6 | 秭地1-6 | 0.99 | 2.49 | 96.52 | 0.00 | -9.6 | -213 | 7.4 | |||||||||||
277.9 | 秭地1-7 | 15.80 | 0.11 | 3.63 | 80.47 | 0.69 | -31.5 | -8.9 | -210 | 6.5 | |||||||||
282.2 | 秭地1-8 | 9.58 | 2.91 | 75.81 | 0.00 | -13.6 | -211 | 6.5 | |||||||||||
285.1 | 秭地1-9 | 9.58 | 0.06 | 3.99 | 86.43 | 0.62 | -30.8 | -12.3 | -214 | 6.2 | |||||||||
288.6 | 秭地1-10 | 69.20 | 0.05 | 2.20 | 28.32 | 0.07 | -28.7 | -10.5 | -193 | 5.1 | |||||||||
299.6 | 秭地1-12 | 70.30 | 0.14 | 3.12 | 26.58 | 0.20 | -27.9 | -9.8 | -191 | 4.3 | |||||||||
306.4 | 秭地1-13 | 50.96 | 0.13 | 3.71 | 45.33 | 0.25 | -31.4 | -10.2 | -193 | 4.7 | |||||||||
311.5 | 秭地1-14 | 33.02 | 0.07 | 3.54 | 63.44 | 0.21 | -30.7 | -12.4 | -201 | 5.1 | |||||||||
317.4 | 秭地1-15 | 27.49 | 0.06 | 2.12 | 70.39 | 0.22 | -28.8 | -9.8 | -197 | 5.7 | |||||||||
324.7 | 秭地1-16 | 77.59 | 0.69 | 0.34 | 1.83 | 19.91 | 1.31 | -29.8 | -34.8 | -11.6 | -189 | 5.3 | |||||||
328.0 | 秭地1-17 | 69.61 | 1.60 | 0.16 | 2.05 | 26.74 | 2.47 | -30.1 | -35.2 | -10.4 | -192 | 4.8 | |||||||
334.7 | 秭地1-18 | 83.24 | 2.13 | 0.43 | 1.90 | 12.73 | 2.98 | -31.7 | -33.4 | -11.9 | -191 | 3.2 | |||||||
351.4 | 秭地1-19 | 86.30 | 1.70 | 0.20 | 1.13 | 10.87 | 2.15 | -30.3 | -34.5 | -10.7 | -192 | 4.8 | |||||||
263.4 | 秭地1-20 | 89.23 | 0.72 | 0.57 | 1.91 | 8.15 | 1.43 | -29.2 | -33.6 | -12.0 | -192 | 3.8 | |||||||
265.9 | 秭地1-22 | 71.88 | 0.83 | 0.15 | 1.68 | 25.64 | 1.35 | -28.7 | -34.2 | -11.8 | -187 | 4.1 | |||||||
渝东南 | 水井沱组 | 1 455.80 | 解 析 气 | Y1-1 | 0.09 | 0.48 | 45.46 | 0.00 | 焦伟伟等[23] | ||||||||||
1 992.28 | Y2-1 | 22.00 | 0.23 | 76.95 | 0.00 | ||||||||||||||
3 802.91 | Y3-1 | 0.05 | 6.98 | 92.97 | 0.00 | ||||||||||||||
3 802.91 | Y3-2 | 4.89 | 21.26 | 73.84 | 0.00 | -0.30 | |||||||||||||
3 823.41 | Y3-3 | 0.76 | 5.44 | 93.84 | 0.00 | -0.70 | |||||||||||||
3 823.41 | Y3-4 | 3.88 | 1.18 | 94.94 | 0.00 | -2.60 | |||||||||||||
3 839.04 | Y3-5 | 0.52 | 4.77 | 94.71 | 0.00 | -0.52 | |||||||||||||
3 839.04 | Y3-6 | 1.94 | 5.52 | 92.54 | 0.00 | -0.85 | |||||||||||||
3 843.84 | Y3-7 | 4.02 | 1.24 | 94.74 | 0.00 | -2.60 | |||||||||||||
3 843.84 | Y3-8 | 3.63 | 2.32 | 94.05 | 0.00 | -2.24 | |||||||||||||
2 915.18 | Y4-1 | 2.22 | 3.14 | 93.76 | 0.00 | -0.16 | |||||||||||||
2 915.18 | Y4-2 | 7.46 | 0.69 | 91.81 | 0.00 | -1.28 |
|
2 页岩气碳同位素倒转与甲烷裂解的关系
2.1 页岩气碳同位素倒转成因
2.1.1 混合机理
2.1.2 甲烷与水反应机理
2.1.3 抬升扩散机理
2.1.4 甲烷裂解早期的聚合机理
2.2 天然气裂解导致页岩气碳同位素倒转的实验证据
表2 裂解天然气(湿度:7.02%)的原始地球化学特征Table 2 The geochemistry characteristics of natural gas(humidity:7.02%) involved in caracking experiment |
组分名称 | CO2 | CH4 | C2H6 | C3H8 | iC4 | nC4 | iC5 | nC5 |
---|---|---|---|---|---|---|---|---|
含量/% | 6.66 | 86.78 | 4.63 | 1.18 | 0.27 | 0.27 | 0.13 | 0.07 |
碳同位素/‰ | -34.64 | -23.63 |
表3 不同温度天然气裂解的产物组成Table 3 The component of products at different temperature in natural gas cracking experiment |
温度 /℃ | 成分/% | 湿度/ % | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
H2 | CO2 | CH4 | C2H6 | C2H4 | C3H8 | C3H6 | iC4 | nC4 | iC5 | nC5 | ||
500 | 0.02 | 6.67 | 88.57 | 4.21 | 0.01 | 0.44 | 0.01 | 0.03 | 0.02 | 0.00 | 0.00 | 5.07 |
525 | 0.04 | 6.81 | 89.62 | 3.18 | 0.01 | 0.29 | 0.02 | 0.02 | 0.02 | 0.00 | 0.00 | 3.79 |
550 | 0.07 | 7.26 | 89.36 | 2.98 | 0.01 | 0.27 | 0.02 | 0.02 | 0.02 | 0.00 | 0.00 | 3.58 |
575 | 0.15 | 7.83 | 88.92 | 2.80 | 0.01 | 0.24 | 0.02 | 0.01 | 0.02 | 0.00 | 0.00 | 3.37 |
600 | 0.18 | 7.91 | 88.98 | 2.68 | 0.01 | 0.21 | 0.01 | 0.01 | 0.02 | 0.00 | 0.00 | 3.19 |
625 | 0.27 | 8.22 | 88.96 | 2.37 | 0.00 | 0.16 | 0.01 | 0.01 | 0.01 | 0.00 | 0.00 | 2.80 |
650 | 0.35 | 8.32 | 89.56 | 1.66 | 0.00 | 0.09 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.94 |
675 | 0.36 | 8.36 | 90.15 | 1.07 | 0.00 | 0.05 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.24 |
700 | 0.52 | 8.58 | 89.97 | 0.88 | 0.00 | 0.04 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.02 |
725 | 0.54 | 8.96 | 89.61 | 0.85 | 0.00 | 0.03 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.98 |
750 | 0.59 | 9.15 | 89.40 | 0.82 | 0.00 | 0.03 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.95 |
775 | 0.61 | 9.31 | 89.25 | 0.80 | 0.00 | 0.03 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.92 |
800 | 0.62 | 9.53 | 89.03 | 0.79 | 0.00 | 0.03 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.91 |
3 高过成熟页岩气中N2的成因、生成与保存
表4 页岩中常见矿物的化学组成Table 4 The chemical composition of common minerals in shales |
| | | |
---|---|---|---|
| | | Na[AlSi3O8] |
| | | K[AlSi3O8] |
| CaSO4 | | Ca[Al2Si2O8] |
| CaCO3 | | Al2Si4O5(OH)4 |
| Ca.Mg(CO3)2 | | (K,Mg,Ca,Na)0.33(Al.Mg)2(Si4O10)(OH)2.nH2O |
| FeCO3 | | (H30,K) Al8(Si, Al )16O40(OH)8 |
微斜长石 | K[AlSi3O8] | | Mg3(Al4O10)(OH)12.nH2O |
表5 中国南方高含氢气的页岩气组成Table 5 The compositions of shale gas samples with high H2 content in South China |
| | | | | | | | | |
---|---|---|---|---|---|---|---|---|---|
| | | | | | | | | |
| | | 90.63 | 0.14 | 0.03 | 2.65 | 5.43 | 1.12 | |
宁218井 | 解析气 | | 3 546.5 | 46.03 | 0.16 | 0.01 | 8.67 | 41.03 | 4.08 |
宁218井 | 解析气 | | 3 558 | 32.41 | 0.10 | 0.01 | 3.65 | 61.14 | 2.69 |