遵义后坝奥陶系红花园组油苗岩石轻烃特征分析

遵义后坝奥陶系红花园组生物碎屑灰岩中发现油苗和沥青,经过气/源岩、沥青/源岩对比,震旦、寒武及奥陶系产层轻烃C₆₊₇结构组成基本一致,奥陶系含油苗灰岩轻烃星图与震旦系泥岩、寒武系沥青砂岩星图较为相似,显示红花园组油苗主要来源于震旦系和下古生界过成熟或高成熟海相烃源岩,油气经历了较长距离的运移,得以在奥陶系中保存下来。这对评价该地区油气前景有重要意义,预示着可能存在一套特殊的含油气组合,存在以O₁h古风化壳储集层为目的层的勘探领域。在兴文—叙永一线以西地区现今下古生界储盖组合保存良好,在适当的构造圈闭中可形成油气藏。志留系和二叠系产层轻烃C₆₊₇与震旦系、寒武系及奥陶系等产层轻烃C₆₊₇明显有别,星图对比性差,表征它们之间成烃母质或沉积环境均有不同。 

CHARACTERISTICS OF LIGHT HYDROCARBON IN OIL SEEPING ROCKS IN THE HONGHUAYUAN FORMATION OF ORDOVICIAN, HOUBA, ZUNYI

Oil seepage and bitumen have been found in biocalcarenite in the Honghuayuan Formation of Ordovician in Houba,Zunyi.Gas/source rock and bitumen/source rock comparisons have indicated that,light hydrocarbon C_(6 7) compositions in the Sinian,Cambrian and Ordovician productive formations are almost the same.Star maps of light hydrocarbon in Ordovician oil seeping limestone,Sinian mudstone and Cambrian bitumen sandstone are similar,which means that,oil seepages in the Honghuayuan Formation mainly come from over mature and high mature marine source rocks in the Lower Palaeozoic.Petroleum migrates for a long distance and is reserved in Ordovician.A set of special oil-bearing composition and an exploration field with the O_1h fossil weathered residuum reservoir as the target may exist.To the west of Xingwen-Xuyong,reservoir and cap formation are kept well in the Lower Palaeozoic.Accumulation may be found in proper tectonic traps.Light hydrocarbon C_(6 7) compositions in Silurian and Permian are quite different from those in Sinian,Cambrian and Ordovician with incomparable star maps,indicating the differences between hydrocarbon generation parent and deposition environment.