摘要
松辽盆地大陆科学钻探工程已经进行了十余年(2005—2016),松科1井于2007年完钻,松科2井于2014年开钻,预计2017年底完钻。该工程的目标是通过实施"2井4孔"钻探,打穿松辽盆地白垩系,获取万米连续高分辨率的陆相地质记录,用以研究白垩纪时期的温室气候变化,以期更好地应对全球变暖使人类面临的挑战。据此确定松科2井的选址原则:地层沉积记录连续;以沉积岩为主,尤其是以湖相细碎屑岩为主;厚度尽可能薄;构造简单;地面施工条件好。松科2井选在松辽盆地徐家围子断陷中沙河子组湖相泥岩最为发育的宋站地区。钻探主要目的层为下白垩统断陷层序的营城组、沙河子组和火石岭组。钻遇主要岩性为含火山岩和火山碎屑岩的砂岩、粉砂岩、泥岩、煤层互层序列,以河湖相反映还原环境的暗色岩系为主。期间穿过断陷层顶(T_4)、底(T_5)界面,上下白垩统界面和白垩系/侏罗系(K/J)界面等反映区域构造-成盆作用的重要地质界线,还会取得与白垩纪超静磁带(CNS)和全球大洋缺氧事件(OAE-1)等重要地质事件相对应的连续岩心记录。
The Continental Scientific Drilling in the Songliao Basin has been done since 2005,which include the SK1,having finished in 2007,and the SK2 that started drilling in 2014 and is expected to finish in 2017.The purposes of the project are as followings,to drilling through the whole Cretaceous sequence of the Songliao Basin,to obtain continuous high resolution continental geological records by the means of the so-called"2wells4holes drilling procedures",to research the Cretaceous greenhouse climate changes in order to be better prepared with the challenge caused by the nowadays global warming event.According to the goals above we proposed the rules for the site selection of the SK2 as follows.Firstly,stratigraphic sedimentary records should be continuous.Secondly,sedimentary rocks are preferred,especially the lacustrine fine clastic rocks.Thirdly,thickness of the overburden cap rocks should be as thin as possible.Fourthly,faults should be avoided of.At last,ground conditions should be as good as possible such as roads,electric power,water supply,and so forth.We finally chose the site of SK2 in the Songzhan area where the lacustrine mudstone is well developed in the Xujiaweizi faulted depression of the Songliao Basin.The major target drilling succession is the Lower Cretaceous,namely, Yingcheng,Shahezi,and Huoshiling Formations. The strata under drilling are interbedding sequence of sandstone,siltstone,mudstone and coal,which are intercalated with volcanic rocks and pyroclastic rocks.They are mainly dark rocks of lacustrine facies which reflect the reduced environment.We shall drill through the top boundary()and bottom boundary(T_5)of rift fill successions,the boundary between the Upper and Lower Cretaceous,the boundary between Cretaceous and Jurassic(K/J).All these boundaries indicate important geological events which reflect changes of regional tectonics and basin fillingstyles.With the continuous coring section,we can also obtain some other important geological records with global meanings such as the Cretaceous normal polarity superchron(CNS)and oceanic anoxic event(OAE-1).