泌阳凹陷湖相碳酸盐岩未成熟石油的形成条件  

Conditions for the formation of immature oil in lacustrine carbonate rocks in Biyang depression

作　　者：邵宏舜[1] 黄杏珍[1] 闫存凤[2] 马万怡[3] 贾敏[3] 

机构地区：[1]中国科学院兰州地质研究所,甘肃兰州730000 [2]中国石油天然气集团公司西北地质研究所,甘肃兰州730020 [3]河南石油勘探局勘探开发研究院,河南南阳473132

出　　处：《地球化学》2002年第3期266-272,共7页Geochimica

基　　金：国家自然科学基金(49872048)

摘　　要：泌阳凹陷下第三系核桃园组H13—H32段湖相白云岩,分布有未熟油的工业性油流,原油来自同层段的湖相泥质白云岩,属自生自储式原油。通过凹陷中心云2井和云1井岩芯的有机地球化学研究,论述了白云岩系未熟油形成的内因和外因。有机质丰度高和优良的成油母质类型(包括被细菌改造“腐泥化”的母质)和良好的岩性组合是早期成油的物质基础;双层水体的咸水碱性环境是早期成油的外界条件。其成烃模式表明,泌阳凹陷湖相碳酸盐岩存在早期和晚期两个成烃高峰期。Lacustrine dolomite measures are widely distributed in Biyang depression, in which <IMG SRC='IMAGE/08090032.JPG' HEIGHT=11 WIDTH=12> and intervals of Hetaoyuan Formation (Lower Tertiary) produce commercial immature oil flow. The results of oil source correlation show that the crude oil is derived from immature source rock, muddy dolomite,at the same position, forming a self generated and self reservoired oil pool. Through the study on organic geochemistry of cores of wells Yun 1 and Yun 2 in the center of the depression, the favorable geological and geochemical conditions for the formation of immature oil can be summarized as follows. (1) The content of organic matter in the source rock is high, and that in dark gray muddy dolomite is in the range of 1.09%～4.8%, showing abundant oil forming matters. (2) The types of organic matters are excellent. Micro compositions of kerogen are mainly composed of the sapropelic matter (51%to 93%) and vitrinite (5.5%to 47%). The source rock is rich in algal bacteria matters and those intensely altered terrigenous higher plants by microorganism, and they jointly constitute the typesⅠand Ⅱof oil forming matters. (3) Brackish saline alkaline depositional environment can enhance the hydrolyzation of organic matter into simple compounds, which is favorable for the formation of hydrocarbon in early chemical process under low temperature. (4) Lacustrine dolomite measures contain mainly muddy dolomite of 12%～32%mud content, with interbedded dolomitic mudstone, siltstone and fine sandstone, and they are favorable for the expelling of immature oil, together with the early dehydration of clay, into reservoir to form oil bed. All these conditions can efficiently promote the formation of immature oil in Biyang depression. There exist two oil generation peaks in the lacustrine dolomite measures in the depression, and the early peak is in the Ro range from 0.42%to 0.58%, overlapping part of the late kerogen thermal degradation intervals starting from 1 950 to 2 150 m in depth.

关 键 词：湖相白云岩 “未成熟”石油 形成条件 泌阳凹陷 有机地球化学 碳酸盐岩 

分 类 号：P618.130.1[天文地球—矿床学] TE12[天文地球—地质学]