四川盆地奥陶系储层发育特征与勘探潜力

四川盆地自震旦系到侏罗系，奥陶系是唯一一个未取得商业性天然气发现的层系。下奥陶统桐梓组和红花园组具有类似寒武系龙王庙组和三叠系嘉陵江组的沉积环境，后两者在台内颗粒滩相碳酸盐岩中都发现了大气田。通过钻井、地震和区域地质资料的分析，提出：①下奥陶统具有形成滩相异常体的地质条件，川东南等地震剖面上发现地层增厚呈丘状反射，是桐梓组-红花园组颗粒碳酸盐岩与膏盐、泥岩等互层的综合反映；②下奥陶统发育下生上储和上生下储两种成藏组合；③借鉴川中寒武系和三叠系的勘探经验，深入开展奥陶系沉积相、古地貌和以输导体系为重点的成藏演化史研究，在异常体发育区实施一口区域探井，有望实现奥陶系勘探的重大突破。

Charateristics and exploration potential of Ordovician reservoirs in Sichuan Basin

The Ordovician has been the only strata with no comericial gas discoveries from the Sinian to Jurassic in Sichuan Basin.The Honghuayuan Fm.and the Tongzi Fm.of the Lower Ordovician share a similar sedimentary environment with the Longwangmiao Fm of the Cambrian and the Jialingjiang Fm of the Triassic,and the latter two formations were proven to contain large gas fields in their carbonates of grain beach facie.Based on an integrated analysis of drilling,seismic and regional geological data of the basin,we obtained the following conclusions.1)The lower Ordovician had the geological conditions needed for forming grain beach.The mound reflections on seismic profiles of southeastern Sichuan Basin are the responses of grain carbonate interbedded with gypsum and mudstone in the Tongzi Fm and the Honghuayuan Fm.2)There are two types of source rock-reservoir combinations in the Lower Ordovician,namely lower source rock-upper reservoir combination and upper source rock-lower reservoir combination.3)According to the exploration expe-riences in the Cambrian and Triassic of central Sichuan Basin,study should be performed in respects of sedimentary facies,paleo-geomorphology and hydrocarbon accumulation and evolution history with carrier system as the focus for exploration in the Ordovician.An exploration well should be emplaced in area with prominent anomaly reflections.