黔西北大方地区龙潭组海陆过渡相烃源岩特征及评价  

Characteristics and evaluation of marine-terrestrial transitional source rocks in the Longtan Formation in the Dafang area,Northwest Guizhou

作　　者：兰叶芳 任传建 潘仕辉 任戍明 LAN Ye-fang;REN Chuan-jian;PAN Shi-hui;REN Shu-ming(School of Mining Engineering,Guizhou University of Engineering Science,Bijie 551700,China)

机构地区：[1]贵州工程应用技术学院矿业工程学院,贵州毕节551700

出　　处：《岩石矿物学杂志》2023年第6期852-867,共16页Acta Petrologica et Mineralogica

基　　金：贵州省科技计划项目(黔科合基础[2017]1407);高层次人才科研启动基金项目(院科合字G2017006号);贵州省青年科技人才成长项目(黔教合KY字[2016]283);创新创业项目(S202210668115)。

摘　　要：黔西北大方地区龙潭组以泥页岩、煤层与砂岩交替互层发育为特点,具有典型的海陆过渡相特征。文章在剖面实测和样品采集的基础上,结合全岩和黏土矿物XRD分析、总有机碳(TOC)含量测定、岩石热解、干酪根显微组分及镜质体反射率(RO)等分析,对研究区龙潭组烃源岩发育特征进行了研究和评价。结果表明:(1)龙潭组矿物以黏土矿物为主,具有较强的吸附能力,但黏土矿物含量与石英含量呈明显的负相关关系(R>0.8),尤其是泥页岩中70%以上的黏土含量以及较低的脆性指数增加了压裂开发的难度。(2)龙潭组有机质丰度受岩性变化控制明显。煤层具有最高的TOC含量(平均值42.9%)和生烃潜量(平均值为2.68 mg/g),显示强大的煤层气生烃潜力;泥页岩生烃潜量均小于2 mg/g,但约有80%样品的TOC含量超过2%,页岩气资源潜力不及煤层气;粉砂岩生烃潜力最差,生烃潜量平均值为0.13 mg/g,TOC含量为1.4%~5.6%,显示一定的致密气潜力。(3)龙潭组有机显微组以壳质组和镜质组占主导,干酪根以Ⅲ型为主,Ⅱ2型为辅,热演化程度高,处于高-过成熟的生干气阶段。(4)煤层更为发育的龙潭组中段是大方地区煤层气、页岩气和致密砂岩气联合勘探的有利层段。The Longtan Formation in the Dafang area of Northwest Guizhou is characterized by alternated shale,coal seams,and sandstones,with typical characteristics of marine-terrestrial transitional facies.On the basis of profile measurement and sample collection,combined with XRD analysis of whole rock and clay minerals,determination of total organic carbon(TOC)measurement,rock pyrolysis,kerogen macerals,and vitrinite reflectance(R_O)analysis,the development characteristics of hydrocarbon source rocks of the Longtan Formation in the study area are studied and evaluated.The results indicate that:(1)The minerals in the rocks of the Longtan Formation are mainly clay minerals with strong adsorption capacity,but there is a significant negative correlation between clay mineral content and quartz content(R>0.8),especially the clay content of over 70%in shale and the lower brittleness index,which is very unfavorable for fracturing development;(2)The abundance of organic matter in the Longtan Formation is significantly controlled by lithology.The coal seam has the highest TOC content(average 42.9%)and hydrocarbon generation potential(average 2.68 mg/g),indicating strong hydrocarbon generation potential of coalbed methane;The hydrocarbon generation potential of shale is less than 2 mg/g,but about 80%of the samples have TOC content exceeding 2%,and the shale gas resource potential is less than that of coalbed methane;Silty sandstone has the worst hydrocarbon generation potential,with an average hydrocarbon generation potential of 0.13 mg/g and a TOC content of 1.4%~5.6%,indicating a certain degree of tight gas potential;(3)The macerals of the Longtan Formation kerogen are mainly composed of liptinite and vitrinite,with typeⅢkerogen being the main type and typeⅡ2 being the auxiliary type.They have a high degree of thermal evolution and are in the stage of high-over mature drygas generation;(4)The middle section of the Longtan Formation,where coal seams are more developed,is a favorable zone for joint exploration of coalbed methan

关 键 词：海陆过渡相 龙潭组 非常规气 烃源岩 黔西北 

分 类 号：P588.2[天文地球—岩石学] P618.13[天文地球—地质学]