四川盆地东南缘林滩场构造二叠系沥青的地球化学特征及意义

Geochemical Characteristics and Its Significance of Permian Bitumen from Lintanchang Structure in Southeast Margin of Sichuan Basin

基于详细的地表和地下地质调研,应用岩石学、有机地球化学和无机地球化学方法,对二叠系古油藏的形成和破坏历史展开详细的研究,认识到二叠系中古油藏具有2种沥青和4种形态,分别为软沥青(晶洞内部方解石—沥青充填;板状沥青充填方解石脉残余孔隙;生物屑边缘浸染状沥青)和炭质沥青(充填于破裂缝中)。林1井地表茅口组灰岩晶洞中充填的沥青应来自于志留系烃源岩。破裂缝中炭质沥青烷烃色谱与志留系泥岩、寒武系泥岩和上震旦统灯影组储层沥青差异明显,沥青主要来源于自身微生物源和藻类,为内源成因;茅口组古油藏原油充注时间为印支期,原油裂解时期为燕山期;沥青为深埋高温和构造挤压作用产物。

Based on the detailed geological studies on the outcrop and wells about Permian,with the methods of petrology,organic and inorganic geochemistry,we make a study on the formation and destruction of Permian paleo-oil pool.Several conclusions obtained are as follows：①There are two types of bitumen,four forms,namely the soft bitumen（calcite-bitumen filling the cave,sheet bitumen filling the residual pore,disseminated bitumen around the bioclast） and semi-graphite（filling in the fracture）.②Bitumen in cave of Maokou limestone originates from Silurian source rock,but semi-graphite in fracture may originate from Permian microorganisms and algae,as endogenous causes.And the alkane chromatography indicates that there is significantly different among the Silurian shale,Cambrian shale and Upper Sinian Dengying Formation bitumen.③The filling time of Maokou paleo-oil pool is Indosinian,and oil cracking period is Yanshanian.The bitumen is the product of deep burial and tectonic compression.