修武盆地下寒武统海相页岩储层及CH4吸附特征

为了研究修武盆地下寒武统荷塘组海相页岩储层及其含气性特征,连续选取富有机质钻井页岩为研究对象,进行有机地球化学分析、岩石学、孔隙度、低温N2吸附、CO2吸附和超临界CH4等温吸附等系列实验。RO值为1.74%~2.32%,平均为2.10%,为高成熟阶段。页岩TOC含量高,平均为3.21%;矿物组成以石英和黏土矿物为主,平均为52.66%和35.56%,并发育少量长石、碳酸盐和黄铁矿。平均孔隙度为2.05%,具低孔特征,平均孔径为8.416 nm,主要发育开放型圆筒状孔隙、层状狭缝形孔隙和细颈广体墨水瓶状孔隙;比表面积和孔体积普遍较高,分别为6.94~46.48 m2/g、0.0042~0.0201 cm3/g,其中微孔提供较大的比表面积,与四川盆地龙马溪组页岩数值相近,表明其具有充足的储气空间。研究区不但具有良好的生气物质基础,而且具有较强的CH4吸附能力,平均吸附量为1.71 m3/t;影响吸附的主要因素是TOC含量和孔隙结构,石英为有利因素,黏土矿物对吸附影响微弱。页岩厚度大、埋深较浅,有机质类型以生烃能力强的Ⅰ型为主,脆性矿物含量高,综合认为该区具有较好的页岩气勘探潜力。

Study on the Lower Cambrian marine shale reservoir and methane adsorption characteristics in Xiuwu Basin

Marine shale of Lower Cambrian Hetang Formation from Well RDZ01 in Xiuwu Basin is selected to study the reservoir and its gas-bearing characteristics by organic geochemical analysis,petrology,porosity,low temperature N2 adsorption,CO2 adsorption and supercritical CH4 isothermal adsorption.ROvalue ranges from1.74%to 2.32%,with an average value of 2.10%,and the maturity of organic matter is high.The total organic carbon(TOC)content is high,with an average of 3.21%.Main components are quartz and clay,52.66%and35.56%,respectively,with a small amount of feldspar,carbonate rock and pyrite are developed.Open cylindrical,layered slit and ink bottle pores are mainly developed in shale,with low porosity(2.05%)and average pore size of 8.416 nm.Specific surface area(SSA)and pore volume are generally high,ranging from 6.94 m2/g to 46.48 m2/g and 0.0042 cm3/g to 0.0201 cm3/g,respectively.SSA of micropores is large,which is close to that of Longmaxi Formation shale in Sichuan Basin,indicating a sufficient gas storage space.Study area has a good material basis for shale gas generation,and the shale has a strong CH4 adsorption capacity(average1.71 m3/t).The main influencing factors are TOC content and pore structure,and quartz is the favorable factor,while clay minerals have little effect.Shale in the study area is characterized by large thickness,shallow burial depth,type I organic matter,strong hydrocarbon generation ability and high content of brittle minerals,having good shale gas exploration potential.