断裂坡折带对海相沉积层序的影响——以鄂尔多斯盆地西缘奥陶系海相碳酸盐岩为例

自断裂坡折带顺斜坡向下常可形成一个垮塌 (滑塌 )—碎屑流—浊流的沉积序列 ,垮塌角砾岩的沉积为其提供了良好的原始孔隙度 ,同沉积期后又为次生孔隙发育提供了有利条件。断裂下降盘通常是聚集油气的有利部位。鄂尔多斯盆地西缘在奥陶纪沉积时期处于断陷海盆的发育阶段 ,断陷海盆边缘的同沉积断裂相当发育 ,对海相沉积层序具有重要的控制作用 ,其滑塌和垮塌角砾岩主要是角砾灰岩 ,相当发育 ,构成良好的油气储集空间。天1井和天 2井的实例对比很好地证明了断裂坡折带对沉积层序的控制并进而控制了油气的成藏条件。盆地西缘是奥陶纪断裂坡折带的发育地区 ,储盖组合完整 ,油气远景良好

Influence of Fractured Slope-break Zone on Sedimentary Sequence: Cases of Ordovician Marine Carbonate Rock in the Western Margin Area of Ordos Basin /

A fractured slope-break zone was initiated by the long-term activity of syndepositional structures and resulted in abrupt steepness change of the depositional slope. Good primary porosity and post-synsedimentary secondary porosity are favorable to set up within a sedimentary sequence of olistostrome-debris-turbidite flows that was commonly deposited downwards along the slope of the zone. The space where there is the downthrown side is generally available to accumulating hydrocarbon. As the western margin area of Ordos Basin was in the stage of development of the marine fault basin during the Ordovician period, synsedimentary faults are quite developed and brecciola-predominated olistostromic breccia are developed also, which made a great deal of reservoir space for hydrocarbon accumulation. Cases of well data that are compared with each other have proved that the Ordovician fractured slope-break zone can influence sedimentary sequence and control the conditions of hydrocarbon accumulation in this area, so that there are good reservoir-cap assemblages and good potential for oil exploration.