酒西盆地砂岩储层碳酸盐胶结物分布及碳、氧稳定同位素富集特征  

Distribution of carbonate cements and enrichment characteristics of carbon and oxygen stable isotopes in sandstone reservoirs in Jiuxi Basin

作　　者：苟迎春[1,2] 张小军[1,2] 李延丽[1] 张世铭[1,2] 秦九妹 吴梁宇[1,2] GOU Yingchun;ZHANG Xiaojun;LI Yanli;ZHANG Shiming;QIN Jiumei;WU Liangyu(Northwest Branch of CNPC Research Institute for Exploration and Development,Lanzhou 730020,China;Key Laboratory of Reservoir Characterization,CNPC,Lanzhou 730020,China;Qinghai Branch of China Petroleum Collective Logging Co.Ltd.,Dunhuang 736202,China)

机构地区：[1]中国石油勘探开发研究院西北分院,甘肃兰州730020 [2]中国石油天然气集团公司油藏描述重点实验室,甘肃兰州730020 [3]中国石油集团测井有限公司青海分公司,甘肃敦煌736202

出　　处：《天然气地球科学》2021年第9期1393-1402,共10页Natural Gas Geoscience

基　　金：中国石油天然气股份有限公司重大科技专项(编号:2012E-3301,2012E-3303)资助。

摘　　要：碳酸盐胶结物是酒西盆地石油沟油田古近系白杨河群间泉子组(N_(1)b_(1))M油组砂岩储层中最重要的自生矿物,其含量及分布是储层定量评价的主要参数。通过矿物学、岩石学和地球化学测试分析认为,该区碳酸盐胶结物主要以方解石为主,少量白云石胶结物,胶结物分布范围为2.11%~56.39%,平均为12.93%。碳酸盐胶结物以基底式、孔隙式结构为主,部分斑点状、环边状。研究表明,不同微相砂体中碳酸盐胶结物相对含量明显不同,其中沙坝微相含量最高,平均为14.6%,河心滩微相含量最低,平均为8.09%,而滞留沉积微相含量居中,平均为7.73%。碳、氧稳定同位素分析表明,δ^(18)O(PDB)值为-11.14‰~-3.25‰,δ^(13)C(PDB)值为-7.32‰~-0.42‰,显示了该区碳酸盐胶结物来自淡水—微咸水环境,与溶解—沉积作用相关。δ^(13)C、δ^(18)O值呈现由深部到浅部逐渐变小、变轻的趋势,说明由深到浅大气淡水影响逐渐增强,水体盐度减小,成岩温度逐渐增高。研究还发现,碳酸盐胶结物δ^(18)O、δ^(13)C值的分异与油气富集程度具较好的分区性,油浸—含油级砂岩碳酸盐胶结物富集δ^(13)C,油斑—油迹级砂岩缺少δ^(18)O同位素,荧光级砂岩胶结物同时缺少δ^(18)O和δ^(13)C同位素。Carbonate cements are the most important authigenic minerals in sandstone reservoirs of Paleogene Baiyanghe Group Jianquanzi Formation(N_(1)b_(1))M oil formation in Shiyougou oilfield,Jiuxi Basin.The content and distribution of carbonate cements are the main parameters of reservoir quantitative evaluation.According to the analysis of mineralogy,petrology and geochemistry,the carbonate cements in this area are mainly calcite and a small amount of dolomite cements.The distribution range of cements is 2.11%-56.39%,with an average of 12.93%.Carbonate cements mainly have base-like structures,some of which are speckled and ringed.The distribution and content of carbonate cements are controlled by sedimentary microfacies.The braided river bar has the highest carbonate content with an average of 14.6%,the riverbank microfacies sand body has an average of 8.09%,and the retained conglomerate carbonate cements at the bottom of the river channel have a medium content with an average of 7.73%.Theδ^(18)O(PDB)andδ^(13)C(PDB)values range from-11.14‰to-3.25‰and from-7.32‰to-0.42‰,respectively,indicating that the carbonate cements in this area come from fresh-bracky-water environment and are related to dissolution-deposition.Theδ^(13)C andδ^(18)O values gradually decrease and become lighter from deep to shallow,indicating that the influence of atmospheric fresh water gradually increases,water salinity decreases and diagenetic temperature increases gradually from deep to shallow.It is also found that the differentiation ofδ^(18)O andδ^(13)C values of carbonate cements and the degree of hydrocarbon enrichment have a good zonation.The carbonate cements of oil-immersed to oil-bearing sandstones are enriched inδ^(13)C,the oil-spot to oil-trace sandstones lackδ^(18)O isotopes,and the fluorium-grade sandstones lack bothδ^(18)O andδ^(13)C isotopes.

关 键 词：碳酸盐胶结物 碳、氧稳定同位素 间泉子段M油组 石油沟油田 酒西盆地 

分 类 号：TE122.113[石油与天然气工程—油气勘探]