盐城凹陷天然气成藏模式  

THE FORMATION MODES OF GAS RESERVOIRS IN YANCHENG SAG

作　　者：马安来[1] 包建平[2] 王培荣[2] 毛凤鸣[3] 侯建国[3] 王文军[3] 

机构地区：[1]中国石油勘探开发科学研究院 [2]江汉石油学院地球化学研究中心 [3]江苏石油勘探局地质科学研究院

出　　处：《天然气工业》2002年第5期23-27,共5页Natural Gas Industry

摘　　要：盐城凹陷发现了中等规模的天然气藏 ,与天然气伴生还有少量凝析油 ,目前对天然气成因还有争议。天然气甲烷含量高、重烃含量低、干燥系数高。天然气碳同位素呈正碳分布 ,δ1 3C1 介于 - 37.7‰～ - 38.1‰。结合地质背景 ,认为天然气为混源气 ,主体为油型裂解气 ,海相古生界烃源岩可能是其主力气源岩。凝析油碳同位素为- 2 8.8‰～ - 30 .5‰ ,全油色谱中含有一定的长链正构烷烃 ,Pr/Ph为 1 .56 ,三环萜烷含量高 ,C2 9Ts、C30 重排藿烷含量高 ,重排甾烷含量高 ,C2 9甾烷 >C2 7甾烷 >C2 8甾烷。石蜡指数、庚烷值表明凝析油为高成熟凝析油 ,C2 9甾烷 2 0S/(2 0S +2 0R)值表明其为成熟原油 ,凝析油为不同成熟度油气混合物 ,主体来源于泰州组烃源岩。凝析油的形成与蒸发分馏作用密不可分。烃类主要充注时间为 6Ma～ 1 5Ma。天然气成藏为“古生新储”A medium-scale gas reservoir was found in Yancheng sag with a small amount of condensate. However, the origin of the natural gas is still in dispute. It is discovered in the gas with high aridity that methane content is high,the quantity of weight hydrocarbon is low, and the carbon isotope is presented as normal carbon distribution with δ13 C1 ranging from -37.7% to -38.1%. Under the geological setting, the natural gas has multiple source origins with the oil-type pyrolysis gas dominating. Its main gas source rocks may be marine Paleozoic strata. The carbon isotope of whole condensate of Well Yancan-1 is about -28.8% ∼ -30.5%. In the whole oil chromatogram, the condensate contains significant long alkanes, with Pr/Ph 1.56, high content of tricycle terpane and large quantity of diahopane C29Ts and C30 and high content of diasterane (C29 C27 > C28). It is suggested that it is an overmature condensate by the paraffin index and the value of heptane. The value of 20s/(20s + 20R) of sterane C29 indicates it is a mature crude oil. This condensate is found to be a mixture of oil and gas with different maturity, mainly originating from hydrocarbon generating rocks in Taizhou Formation. The formation of condensate is ascribed to the process of evaporative fractionation. The hydrocarbon charge experienced for a long time between 6 and 15 magaannuals. This formation mode of gas reservoir is also called 'Paleo-generated and newly-reserved accumulation'.

关 键 词：盐城凹陷 天然气 成藏模式 凝析油 地球化学 流体包裹体 蒸发分馏 

分 类 号：P618.13[天文地球—矿床学]