中扬子区东南缘下组合天然气勘探潜力分析

Exploration Potential of Natural Gas of Lower Assemblage in Southeast Margin of Middle Yangtze Block

中扬子区东南缘震旦纪-早奥陶世处于被动大陆边缘坡折带附近,各种相带频繁交替,生储盖组合配置良好。印支期以来受SN向褶皱造山的影响,后期改造强烈,东部的崇阳-通山地区发育自南向北的逆冲推覆构造,西部桑植-石门地区构造变形较弱,以宽缓的复向斜为主。根据原型盆地分析及基本石油地质条件初步评价,认为桑植-石门复向斜的中部弱变形区及崇阳-通山推覆构造的下盘弱变形区(原地体)是较为有利的勘探区带,桥头、中湖等局部构造是有利的勘探目标。

Southeast margin of middle Yangtze Block was situated in passive continental margin slope of Yangtze block form later Sinian to early Ordovician period, and various sedimentary facies alternated frequently. So source rocks, reservoirs and caprocks was well matched. There was reformated strongly during the latter extensional reformation since Indosinian period. There occurred a certain - scale thrust - nappe tectonics in the Chongyang -Tongshan area, and the deformation was weak relatively in the Sangzhi - Shimen area, the tectonic pattern is broad synclinorium mainly. Based on the analysis of protobasin and evaluation of basic petroleum geological conditions, we think the weakly deformated area in central Sangzhi - Shimen synclinorium and the weakly deformated ＂original geobody under Chongyang - Tongshan thrust - nappe thrust should be favorable block for hydrocarbon exploration, the Qiaotou trap and the Zhonghu trap should be favorable exploration target.