湘西北地区五峰组-龙马溪组生物地层特征及勘探意义  

Biostratigraphic characteristics and exploration significance of Wufeng-Longmaxi Formation in northwestern Hunan

作　　者：张兵 唐书恒[1,2,3] 郗兆栋[1,2,3] 蔺东林 叶亚培 ZHANG Bing;TANG Shuheng;XI Zhaodong;LIN Donglin;YE Yapei(School of Energy Resources,China University of Geosciences(Beijing),Beijing 100083,China;Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Enrichment Mechanism,Ministry of Education,Beijing 100083,China;Beijing Key Laboratory of Unconventional Natural Gas Geological Evaluation and Development Engineering,Beijing 100083,China)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]海相储层演化与油气富集机理教育部重点实验室,北京100083 [3]非常规天然气地质评价与开发工程北京市重点实验室,北京100083

出　　处：《岩性油气藏》2021年第5期11-21,共11页Lithologic Reservoirs

基　　金：国家科技重大专项“四川盆地及周缘页岩气富集规律与重点目标评价”(编号:2017ZX05035)资助。

摘　　要：湘西北地区上奥陶统五峰组—下兰多维列统龙马溪组黑色页岩广泛发育,具有较好的页岩气勘探开发前景。为研究其生物地层特征,开展了XY-3井的化石种类分析,结合笔石与自然伽马(GR)测井曲线,建立了研究区生物笔石序列,并根据各笔石带的有机质丰度、矿物组分、沉积环境的变化,明确研究区页岩气的有利富集层段。结果表明:①研究区五峰组—龙马溪组可划分为8个笔石带:WF2,WF3,WF4,LM2—LM3,LM4,LM5,LM6,LM7,受湘鄂水下高地隆升的影响,研究区缺失LM1带。②WF2—WF3,LM2—LM4笔石带沉积于贫氧化环境,岩性为中碳硅质页岩相。WF4笔石带沉积于氧化环境,岩性为低碳混合质页岩相。LM5—LM7笔石带沉积于氧化环境,岩性为低碳黏土质页岩相。WF2—WF3,LM2—LM4笔石带具有高TOC、高脆性、高孔隙度特征,具有一定的生烃潜力和可压裂性,可以作为页岩气勘探的有利层段。③相比于长宁等地区,研究区富有机质层段厚度相对较薄,有机质丰度相对偏低,因其被湘鄂水下高地影响,较氧化的水体不利于有机质的保存,部分富有机质层段缺失。该研究成果可为湘西北地区的页岩气勘探提供借鉴。The black shale is widely developed in Wufeng Formation of Upper Ordovician and Longmaxi Formation of Lower Llandovery in northwestern Hunan,which has good prospects for shale gas exploration and develop ment.In order to study its biostratigraphic characteristics,the fossil species of well XY-3 were analyzed.Combined with graptolite and natural gamma(GR)logging curves,the sequence of biological graptolite in the study area was established.According to the changes of organic matter abundance,mineral composition and sedimentary environment of each graptolite zone,the favorable enrichment intervals of shale gas in the study area were identified.The results show that:(1)Wufeng-Longmaxi Formation in the study area can be divided into eight graptolite zones:WF2,WF3,WF4,LM2-LM3,LM4,LM5,LM6,LM7.Affected by the uplift of underwater highland in Hunan and Hubei,the study area lacks LM1 zone.(2)WF2-WF3 and LM2-LM4 graptolite zones were deposited in poor oxidation environment,and the lithology was medium carbon siliceous shale facies.WF4 graptolite zone was deposited in oxidation environment,and its lithology was low-carbon mixed shale facies.LM5-LM7 graptolite zone was deposited in oxidation environment,and its lithology was low-carbon clay shale facies.WF2-WF3 and LM2-LM4 graptolite zones were characterized by high TOC,high brittleness and high porosity,and have certain hydrocarbon generation potential and fracturing ability,which can be used as favorable intervals for shale gas exploration.(3)Compared with Changning and other areas,the thickness of organic matter rich layers in the study area was relatively thin,and the abundance of organic matter was relatively low.Because it was affe-cted by the underwater highlands in Hunan and Hubei,the relatively oxidized water body was not conducive to the preservation of organic matter,and some organic matter rich layers were missing.The research results can provide reference for shale gas exploration in northwestern Hunan.

关 键 词：笔石 生物地层 水下高地 五峰组—龙马溪组 上奥陶统 兰多维列统 湘西北地区 

分 类 号：TE122[石油与天然气工程—油气勘探]