四川盆地东南部寒武系含气前景新认识

NEW KNOWLEDGE OF GAS-BEARING POTENTIAL IN CAMBRIAN SYSTEM OF SOUTHEAST SICHUAN BASIN

下古生界寒武系是四川盆地天然气勘探的重要后备领域。在回顾该盆地东南部寒武系勘探历程的基础上,提出了有关勘探方向的三点新认识:一是龙王庙组是寒武系油气勘探的主要目的层;二是加里东期龙王庙组剥蚀区外围的龙王庙期"膏(盐)盆"周缘是龙王庙组勘探的有利区带;三是龙王庙组近期勘探目标应首选孔隙储层发育的区内大中型背斜圈闭作为突破口。综合分析结果认为,川东南地区螺观山、广福坪、相国寺构造均可作为当前勘探突破的目标。这些构造龙王庙组孔隙性储层预测厚度大于15m,闭合面积大于40km2,地震资料可靠程度高,埋藏深度适中,构造保存条件好。

Natural gas reservoirs in lower Paleozoic Cambrian formations are important exploration targets in the Sichuan basin. Through review the exploration history there especially in the southeastern part of this basin, this paper put forward new knowledge on desirable exploration targets from the following three points: (a) the Longwangmiao formation is the main target there; (b) favorable zones will be rims of gypsolith basin in the peripheral of the denuded Longwangmiao formation in the Caledonian movement; (c) large- and middle-scale anticline traps will be the most desirable targets in well-developed porous reservoirs in the Longwangmiao formation. This paper concluded that those structures in the southeastern basin like Luoguanshan, Guangfuping and Xiangguosi are desirable exploration targets with great potential at present after overall study on features and conditions of the above-mentioned structures by highly reliable seismic data which show that the porous reservoirs with a moderate burial depth have thickness of more than 15 m and a trap area of over 40 km2.