咔唑、酚类和二苯并噻吩类化合物在油气运移研究中的应用

原油和源岩中咔唑、酚类和二苯并噻吩类化合物为油气运移研究提供了理想的工具.烷基咔唑浓度、屏蔽和半屏蔽异构体-暴露异构体比值和苯并咔唑比值是很好的运移指标,但源岩有机质输入、沉积环境、热成熟度、初次和二次运移及生物降解作用都可能对这些化合物分布产生影响.不同沉积环境的原油中咔唑类化合物分布差异很大,咔唑类化合物运移参数在成熟度较低时随成熟度增加而增加,在成熟度较高时随成熟度增加而降低,限制了其作为油气运移指标的适用性.烷基酚浓度可以指示油气运移方向,但同样受相和沉积环境、成熟度和生物降解等多种因素影响.同源石油的烷基二苯并噻吩类参数(如4-/1-MDBT,2,4-/1,4-DMDBT和4,6-/1,4-DMDBT)可应用于不同成熟度的原油、生物降解原油和同源石油两期充注的混合油的油气运移示踪,是很好的油气运移评价工具.断陷盆地生成的油气成熟度差异大,相和沉积环境变化快,因此利用分子地球化学指标进行油气运移示踪时,需要综合考虑各种影响因素.

Application of cabazoles, phenols and dibenzothiophenes indexes in hydrocarbon migration research

Chemicals,such as Cabazoles,phenols and dibenzothiophenes,in oils and source rocks may serve as ideal tools for hydrocarbon migration researches.Alkylated carbazoles concentration and shield and semi-shield isomersexposed isomers ratios and benzocarbazole [a]/([a]+[c]) ratios are considered perfect indexes for migration.However,the distribution of these chemicals may be affected by input of organic matters,depositional environment,thermal maturity,primary and secondary migration,and biodegradation.For example,different environments may lead to different distribution of carbazoles,and carbazole migration parameters may increase with maturity increasing at low maturity environment but decrease in a highly matured environment,reducing the reliability of these parameters as the indexes of hydrocarbon migration.Alkylated phenols concentration may serve as migration index but it also affected by many other factors such as sedimentary facies,environments,maturity,and biodegradation.The parameters of alkyldibenzothiophenes of cogenetic oil such as 4-/1-MDBT,2,4-/1,4-DMDBT and 4,6-1,4-DMDBT can fit as migration indexes for oils with different maturity,biodegraded oils,and mixed cogenetic oils of two separated charges,thus can serve as excellent tools for migration direction assessment.It is also suggested that many other factors shall be taken into consideration when molecular geochemistry parameters of crude oils and source rocks are used to trace hydrocarbon migration since these parameters are easily affected by changes in maturity,facies and depositional environment in rifted-basins.