摘要
川南筠连地区作为中国南方首个煤层气商业生产基地,产气层位为上二叠统乐平组,系统开展储层微观孔隙结构特征研究对明确煤层气赋存成藏特征具有重要意义。针对乐平组煤层气评价井煤岩心样品进行了扫描电镜观察和液氮吸附实验,从孔隙成因类型、孔隙结构、孔隙形态及其甲烷吸附性能等方面对微纳米级孔隙发育特征进行了系统分析。结果表明:煤岩微观孔隙可划分为植物组织孔、气孔、矿物铸模孔和晶间孔等4种成因类型。液氮吸附实验BET总孔比表面积平均为2.638 m^(2)/g,BJH总孔体积平均为0.003 7 cm^(3)/g,且两者具有良好的正相关性。BJH平均孔径为5.775~17.842 nm,对总孔比表面积起到主要贡献的为孔径<5 nm的孔隙,对总孔体积具有明显贡献的主要为孔径≥10 nm的孔隙。根据孔径将孔隙划分为:微孔(<5 nm)、小孔(5~10 nm)、中孔(10~100 nm)、大孔(≥100 nm),微孔和小孔是煤中气体吸附的主要空间,进一步推测吸附孔和渗流孔的孔径分界为10 nm。液氮吸附回线可划分为重叠型、半分离半重叠缓降型、半分离半重叠骤降型等3类,并依据回线特征将纳米孔隙形态理想化为开放孔、半封闭孔和墨水瓶状孔等3种模型,各类孔在高阶煤中均有发育。基于具有不同孔隙形态的干燥无灰基煤样甲烷等温吸附实验得到,墨水瓶状孔的甲烷吸附能力最大,半封闭孔和开放孔的吸附能力近似,但都低于墨水瓶状孔。
Junlian area in the south of Sichuan Basin,as the first commercial production base of coalbed methane in South China,has a gas producing bed in the Upper Permian Leping Formation,it is great to study the characteristics of micropore structure to analyze the characteristics of coalbed methane accumulation.In this paper,a large number of Upper Permian Leping coal samples are selected from coalbed methane evaluation wells for scanning electron microscope observation and liquid nitrogen adsorption experiments.The characteristics of pore development at micro and nano scale have been systematically analyzed from the aspects of pore genetic type,pore structure,pore morphology and methane adsorption performance.The results show that micropores of coal are divided into four genetic types:plant tissue pore,stoma,mineral mold hole and intercrystalline pore.Through quantitative analysis of pore structure parameter,it is concluded that the average BET total pore specific surface area is 2.638 m2/g,and the average BJH total pore volume is 0.0037 cm3/g,and there is a good positive correlation between total pore specific surface area and total pore volume.The average BJH pore diameter is 5.775~17.842 nm,and the major contribution to the total specific surface area is from pores with an aperture less than 5 nm,while the major contribution to the total pore volume is from pores greater than 10 nm.According to the diameter of pores,the pore types are divided into four categories:micropore(<5 nm),tiny pore(5~10 nm),mesopore(10~100 nm)and macropore(≥100 nm).Micropores and tiny pores are the main spaces for gas adsorption in high rank coal,and it is further concluded that the boundary value of pore diameter between adsorption pores and free pores of high rank coal is 10 nm.Nitrogen adsorption loops are divided into three types(overlap type,semi-separation and semi-overlap slow drop type,semi-separation and semi-overlap plunge type),and according to the characteristics of the loops,the nanoscale pore morphology is idealized as three typical models,namely open pore,semi-closed pore and inkbottle-shape pore,and all kinds of pores are developed in the high rank coal.Based on the comparison of isothermal adsorption experiments of methane from dry ash free coal samples with different pore morphology,it is found that the adsorption capacity of methane is the highest in inkbottle-shape pores,and the adsorption capacity of semi-closed and open holes is similar but lower than that of inkbottle-shape pores.
作者
段洋利
梁兴
何方雨
周芸
邹辰
梅珏
张涵冰
李磊
叶璁琛
DUAN Yangli;LIANG Xing;HE Fangyu;ZHOU Yun;ZOU Chen;MEI Jue;ZHANG Hanbing;LI Lei;YE Congchen(School of Earth Sciences and Engineering,Xi'an Shiyou University,Xi’an,Shaanxi 710065,China;Shaanxi Key Laboratory of Petroleum Geology;PetroChina Zhejiang Oilfield Company,Hangzhou,Zhejiang 310023,China)
出处
《海相油气地质》
CSCD
北大核心
2024年第2期113-124,共12页
Marine Origin Petroleum Geology
基金
中国石油天然气股份有限公司科学研究与技术开发项目“煤层气新区新层系新领域战略与评价技术研究”(编号:2021DJ2303)资助。
关键词
煤层气
高阶煤
液氮吸附实验
孔隙结构
成因类型
二叠系
筠连地区
coalbed methane
high rank coal
liquid nitrogen adsorption experiment
pore morphology
genetic type
Permian
Jun⁃lian area
作者简介
第一作者:段洋利,硕士研究生在读,研究方向为油气地质学。通信地址:710065,陕西省西安市雁塔区电子二路18号,E-mail:616552922@qq.com;通信作者:梁兴,博士,正高级工程师,主要从事页岩气、煤层气、页岩油、高凝油、常规油气地质工程一体化综合评价与勘探开发规划部署研究以及钻探工程技术、油气生产和科技管理工作。通信地址:310023,浙江省杭州市西湖区留下镇荆山岭,E-mail:liangx85@126.com。
