苏北盆地源岩无双峰生烃和未低熟油

Bimodal hydrocarbon generation and immature oil do not exist in the North Jiangsu Basin

针对苏北盆地“未低熟油”理论盛行,却与勘探效果完全不符合的矛盾,深入剖析前人论著、甄别资料真伪,发现问题如下:误用原始资料,把野值当证据;存在认识盲区,成烃模式缺乏多参数严谨论证,推论不成立;有油/岩亲缘对比,未做油藏/烃灶成熟度匹配一致性验证;脱离实践,认识经不起源岩钻探气测资料等勘探检验。由此证明,所谓“源岩早期非干酪根生油、双峰成烃模式”是假的,未低熟油并不存在。基于此,利用大数据资料分析误差、剔除野值,优选出油/岩的甾烷C29S/(S+R)、C29ββ/(αα+ββ)、萜烷C31S/(S+R)、C32S/(S+R)和CPI、OEP成熟度敏感参数,将干酪根热降解晚期生成原油分为浅成熟油、中成熟油、成熟油3类。Ro>0.70%的中成熟—成熟源岩,与大量的中成熟—成熟油成熟度参数匹配很好;Ro在0.60%~0.70%的浅成熟源岩,与少量的浅成熟油成熟度参数有一些匹配关系;Ro<0.60%的未成熟源岩,无原油可与之匹配,表明没有非干酪根的未低熟油。实践反映,中成熟—成熟源岩钻探气测异常明显,由其供油气的圈闭勘探效果好,已探明石油储量99.83%属此类原油;浅成熟源岩气测无或微弱异常,单靠此类油源不足以形成商业规模的油藏,多数仅见油气显示;未成熟源岩气测无异常,若无异地成熟油供给,圈闭不成藏。

A contradiction in the“immature oil in North Jiangsu Basin”theory prevails and the results of geological exploration is not consistent with it.After making a thorough analysis of previous work and validating the data,the following problems were noticed:misusing of raw data,taking outliers as evidence;multi-parameter consideration is lacking in the hydrocarbon generation model,which makes the inference invalid;the consistency of reservoir and hydrocarbon maturity was not verified after the oil-source correlation;hypotheses do not stand the test of source rock gas logging data and other prospecting results.These indicate that the“non-kerogen source rock early maturation&bimodal hydrocarbon generation model”could be incorrect,and the“immature oil”may not exist.After using big an extensive data set to analyze errors and exclude outliers,the sterane C 29 S/(S+R)and C 29ββ/(αα+ββ),the terpane C 31 S/(S+R)and C 32 S/(S+R),as well as CPI and OEP maturity sensitive parameters of hydrocarbon and rocks were optimized.Crude oil from the thermal degradation of late kerogen can be divided into 3 types:low maturity oil,medium maturity oil and mature oil.It is pointed that the maturity parameters of a large quantity of medium maturity source rocks(Ro>0.70%)could match well with those of medium maturity oil;the maturity parameters of low maturity source rocks(0.60%≤Ro≤0.70%)have only some matching relationships with a small number of low maturity oil maturity parameters;no crude oil matched the immature source rocks(R o<0.60%).The results indicate that the non-kerogen immature oil does not exist.Prominent anomalous data can be detected in the medium maturity and mature source rock gas logging.Hydrocarbon traps with these source rocks usually have good exploration results,and 99.83%of the discovered oil reserves belong to this type.There is little or no anomalous data in the low maturity source rock gas logging.This source rock is unable to form a commercial scale reservoir,and only some shows of hydrocarbon may exist.No anomalous data can be found in immature source rock gas logging.If there is no mature oil supply from other places,reservoirs will not be formed.