PETROLEUM SOURCE ROCKS IN THE TSUGARU BASIN, NORTH HONSHU, JAPAN

研究了青森西部津加鲁盆地新近系第三系泥质沉积的烃源岩潜力。通过元素分析、目视干酪根法、核磁共振和镜质体反射率等方法，对这些沉积物中包含的100多个干酪根和Oga油田新近系第三系沉积物中包含的7个干酪根进行了研究，以供参考。图格鲁盆地新近系第三系沉积物主要为低电位III型或II-III型干酪根。而盆地中部上中新统Odoji组和下上新世赤石组则为高电位I型或II型干酪根。这些地层经历了2000米以上的埋藏成岩作用，有机质成熟程度应超过强烈生油阈值（镜质体反射率值为0.5%）。Odoji组和赤石组沉积物干酪根含量多在1%以上。这些地层的有机地球化学特征与Oga油田公认的烃源岩Onnagawa组和Funakawa组进行了比较。综上所述，从有机质含量、有机质类型和有机质成熟度的综合考虑，认为津加鲁盆地中部上中新统至下上新统奥多吉组和赤石组具有良好的生烃潜力。

This study investigates the petroleum source rock potential of the Neogene Tertiary muddy sediments of the Tsugaru Basin of western Aomori. More than 100 kerogens included in these sediments and 7 kerogens comprised in the Neogene Tertiary sediments of the Oga oil field for reference were examined by elemental analysis, visual kerogen method, nuclear magnetic resonance and vitrinite reflectance. The major part of the Neogene Tertiary sediments in the Thugaru Basin contain low-potential type III or II-III kerogens. But the Upper Miocene Odoji and the Lower Pliocene Akaishi Formation in the central part of the basin include high-potential type I or II kerogens. These formations have suffered burial diagenesis depper than 2,000 meters and their organic matter should be matured to exceed the threshold of intense oil generation (vitrinite reflectance value of 0.5%). The kerogen contents of sediments in the Odoji and the Akaishi Formation are mostly more than 1%. These organic geochemical characters of the formations compare with those of the Onnagawa and the Funakawa formation accepted as source rocks in the Oga oil field. Therefore it is concluded from total viewpoint of the organic content, type and maturity that the Upper Miocene to the Lower Pliocene strate, namely the Odoji and the Akaishi Formation, in the central part of the Tsugaru Basin have good potential for petroleum generation.