鄂尔多斯盆地北部下奥陶统上马家沟组地震相研究

SEISMIC FACIES OF THE LOWER ORDOVICIAN UPPER MAJIAGOU FORMATION IN THE NORTH PART OF EERDUOSI BASIN

鄂尔多斯盆地北部奥陶系内部构造不发育,区域地震剖面以平行反射结构为主要特点。经对代表上马家沟组顶底界的T_9、T_(10)相位及其之间次一级相位进行分析,可在盆地北部划分出3个地震相区和11种地震相类型。不同的地震相类型代表了不同沉积相带或不同岩性组合在地震剖面上的反射结构特征,通过对已钻区地震相类型的划分,就可以探讨未知区的沉积层序和沉积相的演变,并为优选勘探区块提供依据。根据盆地北部上马家沟组储集岩主要发育在白云岩中的区域特点,确定出B、D、E、F、I、J等6种地震相类型为有利的白云岩发育区,这也是天然气勘探的有利区带。

The Ordovician internal structures in the north part of Eerduosi Basin are not well developed. The regional seismic sections are mainly characterized by parallel reflecting configurations. Through analysing the fases T_9 and T_(10) which respectively represent the top and the bottom of Upper Majiagou formation and the secondary rases between T_9 and T_(10), 3 seismic facies areas and 11 seismic facies types can be divided in the north part of the Basin. The different types of seismic facies represent the reflecting configuration characteristics of the different sedimentary facies and lithological association on seismic sections. The sedimentary sequence and facies evolution in unexplored areas can be clarified by dividing the seismic facies types in the drilled areas to provide a basis for optimizing exploration areas. According to the regional characteristics of dolomite reservoirs in upper Majiagou formation in the north part of the Basin, 6 seismic facies i.e. B,D,E,F,I,J,can be classified as areas suitable for the development of dolomite which are also favourable for natural gas exploratin.