华蓥山志留纪地层的再认识及其在油气普查勘探上的意义

REAPPRAISAL OF THE SILURIAN STRATA IN THE HUAYING MOUNTAINS AND ITS SIGNIFICANCE IN OIL AND GAS EXPLORATION

一、华蓥山志留系与“石炭系”华蓥山以东、以北和重庆以下,三峡以上的长江南北两岸的川东地区,70年代后期至今,由原石油工业部,即现在中国石油天然气总公司,四川石油管理局川东气矿,先后在这里勘探到“石炭系”工业气层,现已建成近十个大、中、小型多层气田,其中高产气层常与被称为“石炭系”角砾白云岩密切相关。这个气层分布广,多在100m厚度以内,横向变为或厚或薄的不均一体。但往东南向湖北方向,公认的中石炭统黄龙灰岩,厚度多大于100m,且几乎全是灰岩,至今尚未发现有好的气层或油气显示。该区中石炭世确有浅海碳酸盐沉积,自东向西,自湖北向四川东部和东南部展布。

There is considerable debate concerning the ages of a 5.6m-thick dolostone sequence in the Yanwang valley of Xikou, Yuechi, Sichuan which was interpreted as the“Carboniferous”gas beds by the previous workers. It is contended in this paper that the dolostone sequence were developed as reef complexes in the late Early Silurian, therefore they should be of Silurian age rather than of Devonian or Carboniferous ages.. The seaward side of the shallow marine shelf uplifted in the later stage of the Caledonian orogeny should be considered as a new field of hydrocarbon exploration. The higher indices for oil generation have been identified for the Longmaxi Formation in the lower part of the Lower Silurian strata, and the reef complexes with good reservoir behaviors have also been recognized in the upper part of the overlying Lower Silurian strata overlapped by the Carboniferous strata east, of the Huaying Mountains and interpreted as the highly productive gas beds in the study area.