0 引言
1 地质概况
2 样品与实验
表1 四川盆地中部地区侏罗系沙溪庙组典型天然气样品气体组成Table 1 List of natural gas complsition of Jurassic Shaximiao Formation in the central Sichuan Basin |
序号 | 井号 | 区域 | 层位 | 天然气组成/% | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
CH4 | C2H6 | C3H8 | iC4H10 | nC4H10 | iC5H12 | nC5H12 | CO2 | N2 | ||||
1 | G16 | 公山庙 | J2 s 1 | 64.06 | 14.62 | 11.85 | 1.74 | 4.39 | 1.00 | 1.46 | 0.09 | 0.79 |
2 | GH18 | J2 s 1 | 65.19 | 12.99 | 9.77 | 1.74 | 5.73 | 1.50 | 2.46 | 0.02 | 0.61 | |
3 | GH16 | J2 s 1 | 78.80 | 11.15 | 5.69 | 0.64 | 1.72 | 0.28 | 0.42 | 0.04 | 1.26 | |
4 | J62-1 | 八角场 | J2 s 2 | 85.96 | 6.18 | 2.64 | 0.60 | 1.07 | 0.33 | 0.46 | 0.01 | 2.76 |
5 | J60-6H | J2 s 2 | 84.24 | 7.36 | 3.46 | 0.80 | 1.18 | 0.35 | 0.37 | 0.00 | 2.23 | |
6 | J63-3 | J2 s 2 | 85.11 | 9.37 | 2.92 | 0.57 | 0.68 | 0.23 | 0.20 | 0.00 | 0.93 | |
7 | J70 | J2 s 2 | 84.48 | 9.70 | 3.34 | 0.73 | 0.92 | 0.31 | 0.29 | 0.08 | 0.15 | |
8 | J71H | J2 s 2 | 86.77 | 8.41 | 2.67 | 0.58 | 0.70 | 0.26 | 0.22 | 0.01 | 0.38 | |
9 | JH5 | 金华—秋林 | J2 s 2 | 87.11 | 7.75 | 2.45 | 0.57 | 0.67 | 0.26 | 0.22 | 0.01 | 0.96 |
10 | QL10 | J2 s 2 | 92.08 | 5.33 | 1.63 | 0.24 | 0.46 | 0.11 | 0.15 | / | / | |
11 | Q8 | J2 s 2 | 87.72 | 7.38 | 1.94 | 0.48 | 0.52 | 0.21 | 0.16 | 0.01 | 1.58 | |
12 | QL16 | J2 s 2 | 89.49 | 7.00 | 1.67 | 0.41 | 0.41 | 0.18 | 0.12 | 0.00 | 0.72 |
3 烃源岩评价
4 天然气成因与来源
4.1 天然气组分
表2 四川盆地西部与中部沙溪庙组天然气样品不同公式计算的天然气成熟度Table 2 List of maturity calculated by different formulas for gas samples in the Shaximiao Formation in central and western Sichuan Basin |
序号 | 井号 | 区域 | 层位 | δ13C1/‰ | δ13C2/‰ | 成熟度 R O/% | |||||
---|---|---|---|---|---|---|---|---|---|---|---|
公式(1) | 公式(2) | 公式(3) | 公式(4) | 公式(5) | 公式(6) | ||||||
1 | G16 | 公山庙 | J2 s 1 | -43.3 | -34.0 | 0.70 | / | / | 0.85 | / | 0.93 |
2 | GH18 | J2 s 1 | -47.1 | -35.3 | 0.39 | / | / | 0.49 | / | 0.65 | |
3 | GH16 | J2 s 1 | -47.9 | -35.7 | 0.34 | / | / | 0.44 | / | 0.61 | |
4 | J62-1 | 八角场 | J2 s 2 | -39.2 | -29.7 | 1.32 | / | / | 1.55 | / | 1.36 |
5 | QL18 | J2 s 2 | -37.9 | -27.9 | 0.07 | 0.26 | 0.84 | 0.56 | 0.54 | 0.96 | |
6 | J60-6H | J2 s 2 | -37.7 | -28.8 | 0.07 | 0.27 | 0.84 | 0.58 | 0.42 | 0.98 | |
7 | J63-3 | J2 s 2 | -38.9 | -26.1 | 0.05 | 0.20 | 0.80 | 0.48 | 0.90 | 0.88 | |
8 | J70 | J2 s 2 | -39.3 | -26.2 | 0.05 | 0.18 | 0.78 | 0.45 | 0.87 | 0.85 | |
9 | J71H | J2 s 2 | -38.9 | -25.9 | 0.05 | 0.20 | 0.80 | 0.48 | 0.95 | 0.88 | |
10 | J53 | T3 x | -40.1 | -26.2 | 0.04 | 0.14 | 0.75 | 0.39 | 0.87 | 0.79 | |
11 | QL10 | 秋林—金华 | J2 s 2 | -38.6 | -27.45 | 0.06 | 0.21 | 0.68 | 0.50 | 0.61 | 0.90 |
12 | JN23 | J2 s 2 | -36.3 | -25.0 | 0.11 | 0.39 | 0.85 | 0.73 | 1.22 | 1.11 | |
13 | JH5 | J2 s 2 | -38.5 | -25.4 | 0.06 | 0.22 | 0.68 | 0.51 | 1.09 | 0.91 | |
14 | QL17 | J2 s 2 | -35.7 | -23.9 | 0.13 | 0.46 | 0.91 | 0.81 | 1.65 | 1.18 | |
15 | QL203-H1 | J2 s 2 | -34.4 | -23.6 | 0.18 | 0.65 | 1.04 | 0.99 | 1.81 | 1.33 | |
16 | Q8 | J2 s 2 | -35.8 | -24.2 | 0.12 | 0.45 | 0.90 | 0.79 | 1.53 | 1.17 | |
17 | QL16 | J2 s 2 | -35.1 | -24.8 | 0.15 | 0.54 | 0.97 | 0.89 | 1.29 | 1.25 | |
18 | QL202 | J2 s 2 | -35.54 | -23.78 | 0.13 | 0.48 | 0.93 | 0.83 | 1.72 | 1.20 | |
19 | JN2 | T3 x | -39.4 | -25.3 | 0.05 | 0.17 | 0.62 | 0.44 | 1.12 | 0.84 | |
20 | DX2 | 大兴西 | J2 s | -34.49 | -23.48 | 0.18 | 0.64 | 1.03 | 0.98 | 1.88 | 1.32 |
21 | DX3 | J2 s | -34.05 | -24.21 | 0.20 | 0.72 | 1.08 | 1.06 | 1.53 | 1.37 | |
22 | DX4 | J2 s | -33.54 | -22.45 | 0.23 | 0.82 | 1.14 | 1.15 | 2.51 | 1.44 | |
23 | DXQ5 | J2 s | -33.34 | -22.47 | 0.24 | 0.87 | 1.16 | 1.19 | 2.49 | 1.47 | |
24 | DX5 | T3 x | -32.67 | -20.68 | 0.29 | 1.04 | 1.24 | 1.32 | 4.13 | 1.56 | |
25 | PL2 | 平落坝 | J2 s | -39.21 | -25.45 | 0.05 | 0.18 | 0.64 | 0.46 | 1.08 | 0.85 |
26 | PL1-1 | J2 s | -38.25 | -25.01 | 0.06 | 0.23 | 0.70 | 0.53 | 1.22 | 0.93 | |
27 | PQ1 | J2 s | -38.5 | -25 | 0.06 | 0.22 | 0.68 | 0.51 | 1.22 | 0.91 | |
28 | PL13 | J2 s | -36.8 | -23.5 | 0.09 | 0.34 | 0.81 | 0.68 | 1.87 | 1.07 | |
29 | PQ9 | J2 s | -34.1 | -23.8 | 0.20 | 0.71 | 1.07 | 1.05 | 1.71 | 1.37 | |
30 | CX134-2 | 新场 | J2 s | -36.7 | -24.4 | 0.10 | 0.35 | 0.82 | 0.69 | 1.45 | 1.08 |
31 | CX37 | J2 s | -36.1 | -23 | 0.11 | 0.42 | 0.88 | 0.76 | 2.15 | 1.14 | |
32 | CX454 | J2 s | -35.02 | -22.5 | 0.15 | 0.55 | 0.98 | 0.90 | 2.47 | 1.26 | |
33 | MS1 | J2 s | -33.52 | -23.84 | 0.23 | 0.83 | 1.14 | 1.15 | 1.69 | 1.44 | |
34 | CX132 | J2 s | -33.66 | -21.89 | 0.22 | 0.80 | 1.12 | 1.13 | 2.94 | 1.42 | |
35 | CX117 | J2 s | -34.86 | -23.52 | 0.16 | 0.58 | 0.99 | 0.93 | 1.86 | 1.28 | |
36 | CX105 | J2 s | -33.03 | -23.11 | 0.26 | 0.94 | 1.20 | 1.25 | 2.08 | 1.51 |
公式(1)[35]:煤成气:δ13C1=8.6LgR O-28;油型气:δ13C1=14.8LgR O-41。公式(2)[36]:δ13C1=8.64LgR O-32.8。公式(3)[37]:δ13C1≈48.77LgR O-34.1(R O≤0.9%); δ13C1≈22.42LgR O-34.8(R O>0.9%)。公式(4)[39]:煤成气:δ13C1≈14.12LgR O-34.39;油型气:δ13C1≈15.8LgR O-42.2。公式(5)[39]:δ13C2≈8.16LgR O-25.71。公式(6)[40]:煤成气:δ13C1=25LgR O-37.5;油型气:δ13C1=25LgR O-42.5。样品1—样品4按油型气成熟度公式计算,样品5—样品35按煤成气成熟度公式计算。川西大兴西、平落坝和新场天然气同位素数据据文献[25⁃28,43] |
4.2 天然气碳同位素组成及成因类型
图5 川西和川中地区不同构造单元(a)和八角场地区(b)沙溪庙组δ13C1—δ13C2—δ13C3有机成因烷烃气鉴别(图版据文献[23];J60、J63-1、J62和J61-4天然气碳同位素数据据文献[4,8]) Fig.5 Cross plots of δ13C1, δ13C2 and δ13C3 identification for gas samples from structures in the central and western Sichuan Basin (a), and from the Bajiaochang structure in the central Sichuan Basin (b) |
4.3 天然气轻烃特征
图7 川中地区Q8井(a)和J62-1井(b)沙溪庙组天然气轻烃分布特征 Fig.7 Gas chromatogram of nature gas from the Shaximiao Formation from the Wells Q8 (a) and J62-1 (b) in the central Sichuan Basin |
图8 川中沙溪庙组天然气正庚烷、二甲基环戊烷和甲基环己烷三角图(a)和甲基环戊烷、环己烷和正己烷三角图(b)(底图据文献[33-34])Fig.8 Ternary diagrams of methylcyclohexane (MCyC6), dimethyl-cyclopentanes (DMCyC5) and n-heptane (nC7) (a), cyclohexane (CyC6), methylcyclopentane (MCyC5) and n -hexane (nC6) (b) of gas samples from different strcutures in the central Sichuan Basin(the plate is cited from Refs.[33-34]) |