柴达木盆地西部第三系咸化湖泊烃源岩地质地球化学特征与生烃机理
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摘要
柴达木盆地是在前震旦纪结晶基底上形成的由不同阶段、不同类型盆地叠加起来的复合型盆地。盆地内主要发育了古生界、中生界和新生界三套地层。其中第三系主要发育在盆地西部(简称柴西地区)。
勘探实践证实柴达木盆地西部地区是以第三系咸水湖相为烃源岩的油气富集区,烃源岩以含盐度高(15‰～60‰)、含碳酸岩盐高(>20%)、有机碳含量低(一般Toc<0.5%)、烃转化率高(“A”/Toc一般为20%,最高可达60%以上;Hc/Toc一般为12%,最高可达40%以上)为其特征。且族组分和正烷烃碳同位素具有类似海相有机质的组成特征。
柴西第三系咸水湖相烃源岩有机质生源构成的特殊性造成了烃源岩两期生烃。第一期生烃为Ro<0.6%,主要以可溶有机质直接转化成未熟—低熟石油为主。第二期生烃为Ro>0.6%,主要以干酪根热降解生成成熟石油为主。
综合评价表明,E_3~2生油层分布较广、厚度大,成熟度适中,是柴西尤其是南区及中区油气源的主力烃源层;因此,根据烃源层分布与生烃潜力状况,提出下步勘探应围绕狮子沟—油砂山构造带和油泉子—开特米里克构造带深层(E)以及阿尔金斜坡带等油源丰富的目标进行。并建议注重在浅层寻找未熟油的同时加强在深层找成熟油。
The Qaidam basin, a complex basin superimposed on different stages and different types basin ,is formed from Pre-Sinian crystalline basement. Three sets of strata-Palaeozoic, Mesozoic and Cenozoic strata were developed in the Qaidam basin .Among them ,Tertiary strata is mainly developed in the west region of the basin (briefly called Qaidam basin west region).Exploration proved that the Qaidam basin west region is an oil /gas-bearing area with source rocks of Tertiary salty lacustrine facies , the source rocks are characterized by high salinity (15%~60%)、 high carbonate content (>20%), low organic carbon content(an average Toc <0.5 %, high conversion rate of hydrocarbon (an average "A"/ Toc is 20%, the highest "A"/ Toc is more than 60%; an average Hc/Toc is 12%, the highest Hc/Toc is more than 40% ). Moreover, the composition characteristics of group component and carbon isotopes of n-alkane are similar to that of organic matter in marine facies. In addition, the evolution of source rocks is characteristics of "two stages hydrocarbon-generating due to the particularity of organic matter bio-source composition in source rocks from the Tertiary salty lacustrine facies, the first stage of hydrocarbon-generating is at an early stage (Ro< 0.6%) which immature to low-mature oil was mainly formed by direct conversion of the soluble organic matters, and the second stage is at a late stage(Ro>0.7%) which mature oil was chiefly formed by thermal degration of kerogen.Comprehensive assessment shows that E32 source bed is the predominant source bed of the oil/gas resources for the west region of the Qaidam basin, especially for the south and north region because of its feature of wide distribution, broad thickness and moderate maturation; therefore, based on the distribution of source rocks and potential of hydrocarbon-generating, the author puts forward that Shizigou-Youshashan structure belt ,Youquanzi-Kaitemilike structure belt and Aerjing slope-belt with rich oil resource will become the exploration targets in the next step, meanwhile suggests that exploration for mature oil in deep layer should be emphasized while exploring the immature oil in shallow layer.
勘探实践证实柴达木盆地西部地区是以第三系咸水湖相为烃源岩的油气富集区,烃源岩以含盐度高(15‰～60‰)、含碳酸岩盐高(>20%)、有机碳含量低(一般Toc<0.5%)、烃转化率高(“A”/Toc一般为20%,最高可达60%以上;Hc/Toc一般为12%,最高可达40%以上)为其特征。且族组分和正烷烃碳同位素具有类似海相有机质的组成特征。
柴西第三系咸水湖相烃源岩有机质生源构成的特殊性造成了烃源岩两期生烃。第一期生烃为Ro<0.6%,主要以可溶有机质直接转化成未熟—低熟石油为主。第二期生烃为Ro>0.6%,主要以干酪根热降解生成成熟石油为主。
综合评价表明,E_3~2生油层分布较广、厚度大,成熟度适中,是柴西尤其是南区及中区油气源的主力烃源层;因此,根据烃源层分布与生烃潜力状况,提出下步勘探应围绕狮子沟—油砂山构造带和油泉子—开特米里克构造带深层(E)以及阿尔金斜坡带等油源丰富的目标进行。并建议注重在浅层寻找未熟油的同时加强在深层找成熟油。
The Qaidam basin, a complex basin superimposed on different stages and different types basin ,is formed from Pre-Sinian crystalline basement. Three sets of strata-Palaeozoic, Mesozoic and Cenozoic strata were developed in the Qaidam basin .Among them ,Tertiary strata is mainly developed in the west region of the basin (briefly called Qaidam basin west region).Exploration proved that the Qaidam basin west region is an oil /gas-bearing area with source rocks of Tertiary salty lacustrine facies , the source rocks are characterized by high salinity (15%~60%)、 high carbonate content (>20%), low organic carbon content(an average Toc <0.5 %, high conversion rate of hydrocarbon (an average "A"/ Toc is 20%, the highest "A"/ Toc is more than 60%; an average Hc/Toc is 12%, the highest Hc/Toc is more than 40% ). Moreover, the composition characteristics of group component and carbon isotopes of n-alkane are similar to that of organic matter in marine facies. In addition, the evolution of source rocks is characteristics of "two stages hydrocarbon-generating due to the particularity of organic matter bio-source composition in source rocks from the Tertiary salty lacustrine facies, the first stage of hydrocarbon-generating is at an early stage (Ro< 0.6%) which immature to low-mature oil was mainly formed by direct conversion of the soluble organic matters, and the second stage is at a late stage(Ro>0.7%) which mature oil was chiefly formed by thermal degration of kerogen.Comprehensive assessment shows that E32 source bed is the predominant source bed of the oil/gas resources for the west region of the Qaidam basin, especially for the south and north region because of its feature of wide distribution, broad thickness and moderate maturation; therefore, based on the distribution of source rocks and potential of hydrocarbon-generating, the author puts forward that Shizigou-Youshashan structure belt ,Youquanzi-Kaitemilike structure belt and Aerjing slope-belt with rich oil resource will become the exploration targets in the next step, meanwhile suggests that exploration for mature oil in deep layer should be emphasized while exploring the immature oil in shallow layer.
引文
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2.党玉琪,胡勇,余辉龙.柴达木盆地北缘石油地质,地质出版社,2003.
3.范连顺,王明儒.柴达木盆地茫崖坳陷含油气系统及勘探方向,石油实验地质,1999.1.
4.傅家谟,盛国英,江继纲.膏盐沉积盆地形成的未熟石油,石油与天然气地质,1985.2
5.傅家谟.碳酸盐岩有机地球化学,科学出版社,1989.
6.候读杰,王铁冠等等.陆相地球化学研究,中国地质大学出版社,1995.
7.湖北省石油学会主编.蒸发岩与油气,石油工业出版社,1985:110～116.
8.胡见义,黄第藩等.中国陆相石油地质理论基础[M].北京:石油工业出版社,1984:162～234.
9.黄第藩等.陆相有机质演化和成烃机理,石油工业出版社,1984:17～34.
10.黄第藩等.中国未成熟石油成因机制和成藏条件,石油工业出版社,2003:625～657.
11.黄飞等.中华人民共和国石油天然气行业标准(SY/T5735—1995,陆相烃源岩地球化学评价方法),石油工业出版社,1996.
12.黄汉纯等.柴达木盆地地质与油气预测,地质出版社,1996.
13.黄杏珍等.柴达木盆地的油气形成与寻找油气田方向,甘肃科学技术出版社,1993:212～232.
14.江汉石油学院分析测试研究中心.有机地球化学研究进展,重庆大学出版社,1996.84～91.
15.金强,查明,赵磊.柴达木盆地西部第三系蒸发岩与生油岩共生沉积作用研究,地质科学,2000.4.
16.金强,查明,彭德华.柴达木盆地西部第三系盐湖相有效生油岩的识别,沉积学报,2001.1.
17.李浩等.柴达木盆地西部地区第三纪古湖泊研究,断块油气田,2002.2.
18.李贤庆等.烃源岩有机岩石学研究方法与应用,重庆大学出版社,1997.
19.李贤庆,钟宁宁.低熟源岩中矿物沥青基质的特征与成因,江汉石油学院学报,1997.2
20.梁狄刚等.柴达木盆地北缘和西部油气源对比研究,CNPC油气地化重点实验室、青海油田研究院,内部报告,2001.
21.梁狄刚等主编.第八界全国有机地球化学学术会议论文集,有机地球化学研究新进展,石油工业出版社,2002.140～147.
22.林壬子等.中国地质学会、中国石油学会、中国矿物岩石地球化学学会编,有机地球化学论文集,矿物燃料中多环芳烃的石油地球化学意义,地质出版社,1987.129～140.
23.苗军.柴达木盆地第三纪湖盆古水介质研究,西安石油学院学报,自然科学出版社,2000.4.
24.潘志清等.盐湖相原油和生油岩中芳烃及硫化芳烃的分布特征.石油与天然气地质,1988.4.
25.彭德华等.柴达木盆地油气资源评价,青海油田分公司研究院,内部报告,2002.
26.钱凯,邓宏文.湖相生油岩与古盐度的成因关系,岩石学研究,1983.2.
27.邵宏舜,黄杏珍.茫崖凹陷原油地球化学特征与成油环境,中国科学院兰州地质研究所生物、气体地球化学开放实验室研究年报,甘肃科学出版社,1987.
28.王培荣主编.非烃地球化学和应用,石油工业出版社,2002.143～147.
29.王铁冠等.低熟油气形成理论与分布,石油工业出版社,1995.
30.王铁冠等.中国几种显微组份的成烃机理,沉积学报,1997.2.
31.王玉华等.柴达木盆地北缘地区中新生代地层油气生成与资源评价,科学出版社,2004.
32.邬立言等.生油岩热解快速定量评价,科学出版社,1986.
33.曾国寿等.石油地球化学,石油工业出版社,1993:161～184.
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