烃源岩测井识别与评价方法研究进展

Researches progress in well log recognition and evaluation of source rocks

烃源岩测井识别与定量评价对油气资源潜力勘查、储量评估及非常规油气勘探开发至关重要。烃源岩自身岩性和成熟度等差异、测井序列对烃源岩响应灵敏程度不同以及不同方法适用性区别等导致烃源岩测井评价工作仍受到限制。目前亟需进一步挖掘地球物理测井资料中蕴含的烃源岩信息,搭建烃源岩品质与测井信息之间桥梁,并实现以自生自储为特性的非常规油气烃源岩品质测井精细表征。笔者等首先阐明烃源岩分类及其地质表征参数,并分析不同类别烃源岩在常规测井序列及成像和核磁共振等新技术测井序列上响应特征。烃源岩通常表现为“四高一低”(高GR、高AC、高CNL、高RT和低DEN)测井响应特征。除单因素分析外,可优选交会图及构建敏感参数等实现烃源岩定性识别。而烃源岩有机碳含量(TOC)等参数测井定量预测方面则可采用ΔlgR法、修正ΔlgR法(变基线和变系数)、自然伽马能谱测井法、多元回归法、Litho Scanner测井资料法以及人工智能方法实现。在分别评述不同TOC含量测井计算方法的优缺点和适用条件的基础上,指出通过TOC结合生烃潜量等参数计算可实现烃源岩品质测井综合评价。最后解析烃源岩测井识别与评价工作中存在的问题与发展趋势,以期为油气资源评价及非常规油气勘探开发提供理论指导与技术支撑。

Well log identification and quantitative evaluation of source rock are very important for potential exploration of oil and gas resources,reserve evaluation and unconventional oil and gas exploration and development.The well log evaluation of source rock is still limited due to the variations in lithology and maturity of source rocks,and different sensitivity degrees of various response of well log series,as well as differences in the applicability of various methods.At present,it is in an urgent need to further unravel the source rock information contained in geophysical well log data,and to build a bridge between source rock quality and well log information.In addition,it is also in great need to finely characterize the source rock quality of self-generation and self-storage unconventional hydrocarbon using well logs.In this paper,the classification and geological characterization parameters of source rock are firstly clarified.Then the log response characteristics of different types of source rock in conventional log series and advanced logging techniques such as image logs and Nuclear Magnetic Resonance logging(NMR)are analyzed.The response characteristics of source rock are usually shown by“four high values and one low value”(high natural gamma ray,high sonic transit time,high neutron,high resistivity but low density).In addition to single factor analysis,the crossplots and sensitive parameters can be selected to accomplish the qualitative identification of source rock.The quantitative prediction of total organic carbon content(TOC)and other parameters of source rock can be realized byΔlgR method,modifiedΔlgR method(variable baseline and changing coefficient),natural gamma ray spectrum logging method,multiple regression method,Litho Scanner logging data method and artificial intelligence method.The advantages and disadvantages of different TOC content logging methods and their application conditions are reviewed,and then the comprehensive well log evaluation of source rock quality can be realized by TOC prediction combined with the calculation of hydrocarbon generation potential and other parameters.Finally,the existing problems and development trend in the logging identification and quantitative evaluation of source rock are analyzed in order to provide theoretical guidance and technical support for the evaluation of oil and gas resource,and for unconventional oil and gas exploration and development.