0 引言
1 地质背景
2 研究资料和方法
3 结果
3.1 烃源岩地球化学特征
3.1.1 有机质丰度
表1 川西坳陷梓潼凹陷不同层系烃源岩TOC含量分布Table 1 Distribution of TOC contents in source rocks from different strata in the Zitong Sag, Western Sichuan Depression |
烃源岩层位 | TOC/% | 样品总数 | 不同TOC分布区间样品数 | |||||
---|---|---|---|---|---|---|---|---|
最小值 | 最大值 | 平均值 | 0~0.5% | 0.5%~1.0% | 1.0%~2.0% | 2.0%~6.0% | ||
J1 b | 0.06 | 1.20 | 0.37 | 12 | 9 | 2 | 1 | 0 |
T3 x 5 | 0.44 | 3.67 | 1.59 | 31 | 1 | 5 | 18 | 7 |
T3 x 4 | 0.39 | 5.06 | 1.35 | 52 | 3 | 24 | 14 | 11 |
T3 x 3 | 0.92 | 5.33 | 2.46 | 60 | 0 | 1 | 31 | 28 |
T3 x 2 | 0.52 | 0.96 | 0.70 | 5 | 0 | 5 | 0 | 0 |
T3 t | 0.40 | 2.23 | 1.19 | 48 | 1 | 12 | 34 | 1 |
T3 m | 0.65 | 2.25 | 1.17 | 13 | 0 | 5 | 7 | 1 |
T2 l 4 | 0.02 | 0.75 | 0.16 | 44 | 42 | 2 | 0 | 0 |
3.1.2 有机质成熟度
表2 川西坳陷梓潼凹陷不同层系烃源岩实测镜质体反射率(R O)Table 2 Measured vitrinite reflectance (R O) of the source rocks in different strata from the Zitong Sag, Western Sichuan Depression |
井号 | 层位 | 深度/m | R O/% | 井号 | 层位 | 深度/m | R O/% |
---|---|---|---|---|---|---|---|
YX1 | T3 x 5 | 3 484 | 1.55 | TS1 | T3 x 5 | 3 228 | 1.28 |
YX1 | T3 x 5 | 3 646 | 1.56 | TS1 | T3 x 5 | 3 321 | 1.35 |
YX1 | T3 x 3 | 4 322 | 1.85 | TS1 | T3 x 5 | 3 467 | 1.38 |
YX1 | T3 x 3 | 4 583 | 1.91 | TS1 | T3 x 4 | 3 607 | 1.46 |
YX1 | T3 x 3 | 4 686 | 1.95 | TS1 | T3 x 4 | 3 787 | 1.55 |
YX1 | T3 x 3 | 4 787 | 2.14 | TS1 | T3 x 3 | 4 081 | 1.65 |
YX1 | T3 x 3 | 4 890 | 2.22 | TS1 | T3 x 3 | 4 226 | 1.7 |
YX1 | T3 x 3 | 4 979 | 2.28 | TS1 | T3 x 3 | 4 456 | 1.83 |
YX1 | T3 t | 5 544 | 2.36 | TS1 | T3 x 3 | 4 629 | 2.03 |
YX1 | T3 t | 5 590 | 2.45 | TS1 | T3 x 3 | 4 738 | 2.18 |
YX1 | T3 x 4 | 3 951 | 1.58 | TS1 | T3 x 3 | 4 809 | 2.24 |
YX1 | T3 x 4 | 3 954 | 1.62 | TS1 | T3 x 2 | 5 500 | 2.49 |
YX1 | T3 t | 5 685 | 2.46 | TS1 | T3 t | 5 593 | 2.57 |
YX1 | T3 m | 5 694 | 2.47 | TS1 | T3 t | 5 667 | 2.56 |
YX1 | T3 m | 5 710 | 2.55 | TS1 | T3 t | 5 698 | 2.57 |
YX1 | T3 m | 5 713.5 | 2.57 | TS1 | T3 m | 5 733.5 | 2.59 |
3.1.3 有机质类型
图2 川西坳陷梓潼凹陷不同层系烃源岩有机显微组分(a)MY1井,J1 b,3 504 m,灰色泥岩中有机质以镜质组和丝质体为主,全岩;(b)MY1井,T3 x 5,3 545 m,灰黑色泥岩中有机质以镜质组为主,全岩;(c)MY1井,T3 x 4,3 677.8 m,黑色泥岩中有机质以镜质组为主,全岩;(d)YX1井,T3 t,5 685 m,黑色泥岩中有机质以腐殖无定形体、镜质体为主,干酪根;(e)YX1井,T3 m,5 710 m,黑色泥岩中有机质以腐殖无定形体、镜质体、丝质体为主,干酪根;(f)YX1井,T2 l 4,5 720.4 m,白云岩中有机质以腐泥无定形体、固体沥青为主,干酪根 Fig. 2 Organic macerals in source rocks from different strata of the Zitong Sag, Western Sichuan Depression |
3.2 天然气地球化学特征
表3 川西坳陷梓潼凹陷天然气组分和同位素组成Table 3 Chemical and stable isotopic compositions of natural gas from the Zitong Sag, Western Sichuan Depression |
井号 | 层位 | 深度/m | 组分/% | C1/C1-5 | δ13C/‰ | δD1 /‰ | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
CH4 | C2H6 | C3H8 | C4H10 | C5H12 | N2 | CO2 | H2S | δ13C1 | δ13C2 | δ13C3 | |||||
MY1 | T3 x 4 | 3 931~3 940 | 88.99 | 6.40 | 1.42 | 0.62 | 0.185 | 1.41 | 0.98 | 0 | 0.912 | -35.7 | -23.5 | -19.9 | / |
YX1 | T2 l 4 | 5 715~5 723 | 92.92 | 0.21 | 0 | 0 | 0 | 0.38 | 6.49 | 0.001 2 | 0.998 | -34.7 | -29.9 | / | -149 |
YX1 | T2 l 4 | 5 715~5 723 | 92.89 | 0.19 | 0 | 0 | 0 | 0.97 | 5.95 | 0.001 2 | 0.998 | -35.1 | -30.1 | / | -150 |
|
图4 川西坳陷梓潼凹陷天然气C1/C1 - 5与CH4(a)以及N2与CO2(b)相关图(川西气田和新场气田数据分别来自WU等[6]和WU等[5])Fig.4 Correlation diagrams of C1/C1 - 5 versus CH4(a) and N2 versus CO2(b) of natural gas from the Zitong Sag, Western Sichuan Depression (the data of natural gas from the Chuanxi and Xinchang gas fields are from WU et al.[6] and WU et al.[5], respectively) |
4 讨论
4.1 烃源岩品质
图5 川西坳陷梓潼凹陷三叠系与YS1井二叠系烃源岩S 1+S 2与TOC相关图(陆相煤系和海相烃源岩划分范围据陈建平等[28-29])Fig.5 Correlation diagrams between S 1+S 2 and TOC contents in the Triassic source rocks in the Zitong Sag and Permian source rocks from Well YS1, Western Sichuan Depression (the ranges for terrigenous coal-measure source rocks and marine source rocks are cited from CHEN et al.[28-29]) |
4.2 天然气成因
图6 川西坳陷梓潼凹陷天然气δ13C2与δ13C1(a)和δD1(b)相关图(底图分别据ROONEY等[33]和WANG等[36];川西气田和新场气田数据分别来自WU等[5-6])Fig.6 Correlation diagrams of δ13C2 versus δ13C1 (a) and δD1 (b) of natural gas from the Zitong Sag, Western Sichuan Depression (modified after ROONEY et al.[33] and WANG et al.[36], respectively, and the data of natural gas from the Chuanxi and Xinchang gas fields are cited from WU et al.[5-6], respectively) |