塔里木盆地中深地区寒武系盐下白云岩油气来源及差异聚集  

Origin and differential accumulation of hydrocarbons in Cambrian sub-salt dolomite reservoirs in Zhongshen Area,Tarim Basin,NW China

作　　者：张纪智[1] 王招明[2] 杨海军[2] 徐志明[1] 肖中尧[2] 李中璇 

机构地区：[1]西南石油大学地球科学与技术学院,成都610500 [2]中国石油塔里木油田勘探开发研究院,新疆库尔勒841000

出　　处：《石油勘探与开发》2017年第1期40-47,共8页Petroleum Exploration and Development

摘　　要：基于塔里木盆地中深地区储集层样品、原油样品和天然气样品的地球化学特征分析,研究中深地区寒武系盐下白云岩油气来源及油、气差异聚集现象。通过质谱检测发现储集层及原油样品重排甾烷含量低、C_(28)甾烷含量高,伽马蜡烷含量高,原油中存在芳基类异戊二烯烃化合物;通过天然气组成分析发现N_2含量低,为0.24%~4.02%。由此判断油气来源于寒武系—下奥陶统烃源岩。中寒武统天然气δ^(13)C1值为-51.4‰^-44.7‰,干燥系数为0.65~0.78,为原油伴生气;下寒武统天然气δ^(13)C1值为-41.4‰^-40.6‰,干燥系数为0.99,为原油裂解气。塔里木盆地深层存在硫酸盐热化学还原反应生成的高含H_2S裂解气的充注,中寒武统储集层物性差、裂缝网络体系不发育,故充注程度低,天然气中H_2S含量低(0.003 8%~0.200 0%);下寒武统储集层物性好、裂缝网络体系发育,故充注程度高,天然气中H_2S含量也高(3.25%~8.20%)。综上,塔里木盆地中深地区寒武系盐下白云岩油气来源于寒武系—下奥陶统烃源岩,其差异聚集是储集层物性以及裂缝网络体系发育程度的综合影响所致。The origin and differential accumulation of hydrocarbons in the Cambrian sub-salt dolomite reservoirs in Zhongshen Area were studied based on comprehensive geochemical analysis of core samples, crude oil samples and natural gas samples. Mass spectrometric detection shows the core samples and crude oil samples are characterized by high C28 sterane content, low diasterane content, high gammacerane content and abundant aryl-Isoprenoids, and the associated gas has a low nitrogen content of 0.24%-4.02%, so it is inferred that the oil and gas are derived from Cambrian - Lower Ordovician source rock. The natural gas in the Middle Cambrian has a methane carbon isotope value of-51.4‰ - -44.7‰ and dryness coefficient of 0.65-0.78, representing associated gas, and the natural gas in the Lower Cambrian has a methane carbon isotope value of -41.4‰- -40.6‰, and dryness coefficient of 0.99, representing cracking gas. The deep formations in the Tarim Basin contain cracking gas with high H2S content produced by thermo-chemical sulfate reduction （TSR）. Due to the poorer reservoir properties and undeveloped fracture network system, the Middle Cambrian reservoirs have low charging degree of this kind of gas, so low H2S content （0.003 8%-0.200 0%）; in contrast, with good reservoir properties and developed fracture network system, the Lower Cambrian reservoirs have a higher charging degree of this kind of gas, and thus high H2S content of 3.25%-8.20%. In summary, the oil and gas of Cambrian sub-salt dolomite reservoirs in Zhongshen Area are derived from Cambrian - Lower Ordovician source rock, and the differential accumulation of gas is the joint effect of reservoir physical property and development degree of fracture network system.

关 键 词：塔里木盆地 中深地区 盐下白云岩 油气来源 油气差异聚集 

分 类 号：TE122[石油与天然气工程—油气勘探]