摘要
以追踪煤型气源岩的δ13 C1-Ro 关系式计算出对应天然气的Ro 值 ,除以源岩实测Ro 梯度值 ,求得天然气对应源岩深度 ,减去天然气产层深度即得天然气运移距离 ,进而实现对川西坳陷中段陆相天然气源岩的定量追踪。有机质生气门限 (Ro 为 0 .80 %～ 1.0 0 % ,对应古埋深 2 0 0 0～ 2 5 0 0m)配合沉积和构造等地质条件 ,决定着同层位不同地区源岩生气高峰时间有早有晚 ,进而控制着不同时期天然气运移方向 :须五沉积期 ,鸭子河地区小塘子、马鞍塘组均达生气高峰 ,须五段沉积末 ,须三段达生气高峰期 ,天然气从鸭子河向孝泉—新场—合兴场等方向运聚 ;沙溪庙组末—遂宁组早期 ,丰谷、孝泉须三段先于合兴场—新场地区达生气高峰 ,天然气由丰谷、孝泉向新场—合兴场方向运聚 ;遂宁组沉积晚期 ,丰谷须四段达生气高峰 ,天然气向新场方向运聚 ;遂宁组末—蓬莱镇组早中期 ,孝泉须四段达生气高峰 ,天然气经新场向丰谷方向运聚 ;蓬莱镇组晚期 ,合兴场须五段依次先于新场、孝泉达生气高峰 ,天然气向新场—孝泉方向运聚。据此 ,丰谷须四段、合兴场须二段是天然气富集的有利地区 ,新场是从侏罗系到须二段天然气富集的最有利地区。
The gas migration distance may be obtained from the burial depth of source rocks minus that of gas producing zone,in which the former can be acquir ed by the R o value's being divided by the measured R o gradient valu e and the R o value correspounding to the gas can be calculated by δ 13 C 1- R o relation used for trailing coal type gas source roc ks,thus realizing a quantitatively trailing research on the continental natural gas source rocks in the middle section of West Sichuan Depression.The most activ e gas generation time of the source rocks at different areas in the same horizo n may be early or late,which was dependent upon the gas generation thresholds of organic matters (commonly the R o are 0.80%～1.00%,the correspondent anci ent burial depths being 2 000～2 500 m) and unbalanced sedimentary and tectonic evolution in various regions,thus controlling the gas migration directions at di fferent periods:because,in T 3 x 5 depositional stage,the Xiaotangzi and Ma'antang Formations at Yazihe region entered into their peak gas generation and at the end of T 3 x 5 depositional stage,the T 3 x 3 reached to it s most active gas generation time,natural gas migrated from Yazihe to Xiaoquan Xinchang Hexingchang,then it was accumulated;since,at the end of Shaximiao Ag e and in Early Suining Age,T 3 x 3 at Fenggu and Xiaoquan was prior to the one at Hexingchang Xinchang to enter into its peak gas generation,natural gas migrated from Fenggu and Xiaoquan to Xinchang Hexingchang,then it was accumulat ed;owing to the fact that,in Late Suining Age,T 3 x 5 Fenggu reached to i ts most active gas generation time,natural gas migrated from Fenggu to Xinchang ,then it was accumulated;because,at the end of Suining Age and in Early Middle Penglaizhen Age,T 3 x 4 at Xiaoquan reached to its peak gas generation,na tural gas migrated to Fenggu through Xinchang,then it was accumulated;and owing to the fact that in Late Penglaizhen Age,T 3 x 5 at Hexingchang was prior to the one at Xinchang and Xiaoquan to enter into its peak gas generation,natur al gas migrated to Xinchang Xiaoquan,then it was accumulated.For this reason,T 3 x 4 at Fenggu and T 3 x 2 at Hexingchang are beneficial to natu ral gas accumulation and Xinchang is the most beneficial region for natural gas accumulation in the strata from Jurassic to T 3 x 2.
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2002年第3期14-17,共4页
Natural Gas Industry
关键词
川西坳陷
陆相
四川盆地
天然气
碳同位素
侏罗系
上三叠统
源岩
Sichuan Basin,West,Depression,Natur al gas,Carbon isotope,Jurassic Period,Late Triassic Epoch,Source rock
