松辽盆地南部长岭断陷营城组火山岩系储层固体沥青的地球化学特征以及成因分析

THE GEOCHEMICAL CHARACTERISTICS AND ORIGIN OF SOLID BITUMEN FROM VOLCANIC ROCK RESERVOIR OF YINGCHENG FORMATION IN CHANGLING FAULTED DEPRESSION

松辽盆地南部长岭断陷深层营城组广泛分布火山岩系储集层，天然气成藏条件优越，具有较好的勘探前帚。根据长岭断陷YS1井与D2井营城组火山岩储层固体沥青的显微特征、抽提物中饱和烃与芳烃组成特征以及储层流体包裹体均一化温度等资料，分析探讨储层固体沥青的来源、成藏期次及成因机制。结果表明，研究区储层固体沥青为无定形状，无荧光特征，充填于岩石的缝隙之中，其抽提物饱和烃中正构烷烃分布呈单峰态前峰型分布，nC21^-／nC22^＋大于1，奇偶优势不明显，成熟度偏高，Pr／Ph小于1，β-胡萝卜烷、孕甾烷与升孕甾烷以及伽玛蜡烷指数丰度值低；芳烃化合物中菲、惹烯、荧蒽、芘与屈相对丰度高，缺少卡达烯、花、联苯、萘等化合物，三芴化舍物中硫芴、芴的相对丰度高，与饱和烃生标指示特征具有较好的匹配性。这些特征反映研究区储层固体沥青生源母质为低等生物或者藻类，高等植物贡献少，形成于微成水的还原环境。营城组火山岩储层中含烃类盐水包裹体均一化温度分布范围为126℃～130℃与146℃～160℃，石英矿物裂隙的液态烃类包裹体的成藏期为嫩江期，与固体沥青的成藏期相近。根据储层抽提物生物标志物分布及天然气地球化学特征综合分析，研究区储层固体沥青为营城组源岩生成的原油热蚀变作用的产物，有气洗作用的影响。

Changling faulted depression is a continental volcanic rock basin where the accumulation conditions of natural gas is favorable with the foreground of gas reservoir exploration preferable. On the basis of measurement and analysis of volcanic rocks, saturate and aromatic hydrocarbons, the resources, stages and origin of solid bitumen are studied. It is showed that the solid bitumen is characterized by non fluorescent and irregular shape filled in the fractures of rocks. The distribution of normal paraffin hydrocarbons is performed by single peaked shape,nC^21-/nC^22＋〉 1,non obvious odd/even predominance,suggesting that the maturity of solid bitumen is higher. Also the Pr/Ph〈1 , the relatively lower abundance of β-carotane, pregnane and homopregnane, and lower ratios of gammacerane/C30 hopanes reflect that the solid bitumen is generated in a reduction and brackish lacustrine environment. anes and terpanes in saturated hydrocarbon,it According to the allocation and composition of steris thought that the solid bitumen is originated from ordinary aquatic organisms primarily with minor contribution of higher plants. The homogenization temperature from salted fluid inclusions is from 126 ℃to 130 ℃and 146 ℃ to 160 ℃ ,corresponding to sedimentary period of Nenjiang Formation,representing the filling stage of solid bitumen. According to the charateristics of biomarkers and natural gas geochemistry,solid bitumen is primarily cracked by oils derived from the Yingcheng Formation, and undergone gas deasphalting process in the late stage.