鄂尔多斯盆地南缘构造特征及下古生界天然气勘探前景

STRUCTURAL CHARACTERISTICS AND NATURAL GAS POTENTIAL OF LOWER PALEOZOIC IN THE SOUTH MARGIN OF ORDOS BASIN

鄂尔多斯盆地南缘现令构造格局受控于自南向北扩展的两个逆冲推覆体系，上、下古生界之间及基底与盖层之间均存在滑脱层，其东段和西段构造缩短率分别为１８．６％和４．８％。构造变形的主体是燕山期逆冲推覆构造，其前缘带是勘探下古生界构造类气藏的有利区带，且以东北部地区勘探风化壳型气藏最有利；前缘外带保存条件最好，以非构造圈闭为主，是本区最有勘探前景的地区。

The present-day structural framework of the south margin of Ordos basin (the region to the north of Weihe basin) is segmented into zones from east to west, divided into belts from north to south and controlled by two thrust nappes expanding from south to north. There are two decollement formetions between Upper and Lower Paleozoic and between basement and sedimentary cover. The constrictive rate of tectonic in east and west zones is 18. 6% and 4. 8% respectively. The thrust nappe of Yanshan cycle is the main body of the structural deformation in this region. From the view-point of play assessment, the front belt of the nappes is a play for exploring structural gas traps, especially the weathering crust gas traps of Lower Paleozoic; and the outer front belt, due to its best preservation condition for gas, would be the most prospective area for non-structural trap exploration.