有机质页岩孔隙分形模型的适用性研究
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摘要
为了深入研究分形理论模型计算不同尺度孔隙分形维数的适用性,以焦页1井龙马溪组页岩与慈页1井牛蹄塘组页岩的钻井岩心样品为研究对象,采用CO_2和N_2等温吸附试验,获得了2组页岩微孔与介孔的吸附数据,并分别结合微孔分形模型和FHH分形模型计算了微孔与介孔的分形维数,讨论了2种模型的有效性。研究结果表明:微孔分形模型适用于计算CO_2吸附数据,可有效表征页岩微孔的分形维数;而选FHH分形模型适用于计算N_2吸附的高压段数据,可有效表征页岩介孔的分形维数。微孔与介孔可具有不同的分形结构,页岩孔隙结构的评价应综合考虑两类孔隙的分形维数。
In order to deeply study the adaptability of the fractal theory model to calculate the fractal dimension of the different size pores,with the drilling rock core samples of the shale in Longmaxi Formation from Jiaoye No.1 Well and the shale in Niutitang Formation from Ciye No.1 Well as the study objects,the CO_2 and N_2 isotherm adsorption tests were applied to get the micropore and mesopore adsorption data of the shale from the two formations. And individually to combine with the micropore fractal model and the FHH fractal model,the micropore and mesopore fractal dimensions were calculated. The efficiency of the two models was discussed. The study results showed that the micropore fractal model was suitable to calculate CO_2 adsorption data and could effectively characterize the fractal dimension of micropore in shales. The FHH fractal model would be suitable to calculate the high pressure sectional data of the N_2 adsorption and could effectively characterize the mesopore fractal dimension of shales. The micropore and mesopore could have different fractal structures. The evaluation of the shale pore structure should comprehensively consider the fractal dimensions of two type pores.
In order to deeply study the adaptability of the fractal theory model to calculate the fractal dimension of the different size pores,with the drilling rock core samples of the shale in Longmaxi Formation from Jiaoye No.1 Well and the shale in Niutitang Formation from Ciye No.1 Well as the study objects,the CO_2 and N_2 isotherm adsorption tests were applied to get the micropore and mesopore adsorption data of the shale from the two formations. And individually to combine with the micropore fractal model and the FHH fractal model,the micropore and mesopore fractal dimensions were calculated. The efficiency of the two models was discussed. The study results showed that the micropore fractal model was suitable to calculate CO_2 adsorption data and could effectively characterize the fractal dimension of micropore in shales. The FHH fractal model would be suitable to calculate the high pressure sectional data of the N_2 adsorption and could effectively characterize the mesopore fractal dimension of shales. The micropore and mesopore could have different fractal structures. The evaluation of the shale pore structure should comprehensively consider the fractal dimensions of two type pores.
引文
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[32]李相方,蒲云超,孙长宇,等.煤层气与页岩气吸附/解吸的理论再认识[J].石油学报,2014,35(6):1113-1129.LI Xiangfang,PU Yunchao,SUN Changyu.Recognition of adsorption/desorption theory in coalbed methane reservoir and shale gas reservoir[J].Acta Petrolei Sinica,2014,35(6):1113-1129.
[2] ZOU C N,YANG Z,PAN S Q,et al.Shale gas formation and occurrence in China:an overview of the current status and future potential[J].Acta Geologica Sinica,2016,90(4):1249-1283.
[3]邹才能,董大忠,王玉满,等.中国页岩气特征、挑战及前景(一)[J].石油勘探与开发,2015,42(6):689-701.ZOU Caineng,DONG Dazhong,WANG Yuman,et al. Shale gas in China:characteristics,challenges and prospects(I)[J].Petroleum Exploration and Development,2015,42(6):689-701.
[4] CURTIS J B. Fractured shale-gas systems[J]. AAPG Bulletin,2002,86:1921-1938.
[5] LI A,DING W L,HE J H,et al.Investigation of pore structure and fractal characteristics of organic-rich shale reservoirs:acase study of Lower Cambrian Qiongzhusi Formation in Malong Block of eastern Yunnan province,south China[J]. Marine and Petroleum Geology,2016,70:46-57.
[6] YIN H,ZHOU J P,JIANG Y D,et al.Physical and structural changes in shale associated with supercritical CO2exposure[J]. Fuel,2016,184:289-303.
[7] ZHOU L,KANG Z H.Fractal characterization of pores in shales using NMR:acase study from the Lower Cambrian Niutitang Formation in the Middle Yangtze Platform,southwest China[J]. Journal of Natural Gas Science and Engineering,2016,35:860-872.
[8] SHAO X H,PANG X Q,LI Q W,et al.Pore structure and fractal characteristics of organic-rich shales:acase study of the Lower Silurian Longmaxi Shales in the Sichuan Basin,SW China[J].Marine and Petroleum Geology,2017,80:192-202.
[9] YANG R,HE S,YI J Z.Nano-scale pore structure and fractal dimension of organic-rich Wufeng-Longmaxi Shale from Jiaoshiba Area,Sichuan Basin:investigations using FE-SEM,gas adsorption and helium pycnometry[J].Marine and Petroleum Geology,2016,80:27-45.
[10]郭彤楼,刘若冰.复杂构造区高演化程度海相页岩气勘探突破的启示:以四川盆地东部盆缘JY1井为例[J].天然气地球科学,2013,24(4):643-651.GUO Tonglou,LIU Ruobing. Implications from marine shale gas exploration breakthrough in complicated structural area at high thermal stage:taking Longmaxi Formation in Well JY1 as an example[J].Natural Gas Geoscience,2013,24(4):643-651.
[11] CLARKSON C R,SOLANO N,BUSTIN R M,et al.Pore structure characterization of north American shale gas reservoirs using USANS/SANS,gas adsorption,and mercury intrusion[J]. Fuel,2013,130(1):606-616.
[12] PFEIFER P,AVNIR D.Chemistry non-integral dimensions between two and three I:fractal theory of heterogeneous surfaces[J].Journal of Chemical Physics,1983,79(7):3558-3565.
[13] MEDEK J,WEISHAUPTOVA Z.The Microporous phase of carbonaceous substances and its fractal dimension[J]. Fuel,2000,79(13):1621-1626.
[14] YU B,CHENG P.A fractal permeability model for bi-dispersed porous media[J]. International Journal of Heat and Mass Transfer,2002,45:2983-2993.
[15] DATHE A,EINS S,NIEMEYER J,et al.The surface fractal dimension of the soil-pore interface as measured by image analysis[J].Geoderma,2001,103:203-229.
[16] BIRD N,DIAZ M C,SAA A,et al. Fractal and multifractal analysis of pore-scale images of soil[J].Journal of Hydrology,2006,322(1-4):211-219.
[17] YANG F,NING Z F,LIU H Q. Fractal characteristics of shales from a shale gas reservoir in the Sichuan Basin,China[J]. Fuel,2014,115:378-384.
[18] WANG M,XUE H T,TIAN S S,et al. Fractal characteristics of Upper Cretaceous lacustrine shale from the Songliao Basin,NE China[J].Marine and Petroleum Geology,2015,67:144-153.
[19] PFEIFER P,OBERT M,COLE M W.Fractal BET and FHH theories of adsorption:a comparative study[J]. Proceedings of the Royal Society of London A:Mathematical, Physical and Engineering Sciences,1989,423:169-188.
[20] ISMAIL M K,PFEIFER P.Fractal analysis and surface roughness of nonporous carbon fibers and carbon blacks[J]. Langmuir,1994,10(5):1532-1538.
[21] AVNIR D,JARONIEC M.An isotherm equation for adsorption on fractal surfaces of heterogeneous porous materials[J]. Langmuir,1989,5(6):1431-1433.
[22] QI H,MA J,WONG P Z.Adsorption isotherms of fractal surfaces[J].Colloids and Surfaces A,2002,206(1-3):401-407.
[23]金彦任,黄振兴.吸附与孔径分布[M].北京:国防工业出版社,2015.
[24] JARONIEC M.Evaluation of the fractal dimension of microporous activated carbons[J].Fuel,1990,69(12):1573-1574.
[25] JARONIEC M,LU X C,MADEY R. Correlation between the fractal dimension and the microporous structure of a solid[J].Monatshefte Fur Chemie,1991,122(8/9):577-584.
[26] AVNIR D,PFEIFER P.Fractal dimension in chemistry,an intensive characterization of surface irregularity[J]. Nouveau Journal de Chimie-new Journal of Chemistry,1983,7(2):71-72.
[27] JARONIE C M,LU X,MADEY R,et al.Evaluation of structural heterogeneities and surface irregularities of microporous solids[J].Materials Chemistry and Physics,1990,26(1):87-97.
[28] JARONIEC M,GILPIN R K,CHOMA J.Correlation between microporosity and fractal dimension of active carbons[J]. Carbon,1993,31(2):325-331.
[29] CHOMA J,JARONIEC M,PIOTROWSKA J. On the mesopore correction of adsorption data used for characterizing microporous structure of activated carbons[J].Materials Chemistry and Physics,1987,18(4):409-421.
[30] DUBININ M M. Generalization of the theory of volume filling of micropores to non-homogeneous microporous structures[J]. Carbon,1985,23(4):373-380.
[31] STOECKLI H F,BALLERINI L,DEBERNARDINI S.On the evolution of micropore widths and areas in the course of activation[J].Carbon,1989,27(3):501-502.
[32]李相方,蒲云超,孙长宇,等.煤层气与页岩气吸附/解吸的理论再认识[J].石油学报,2014,35(6):1113-1129.LI Xiangfang,PU Yunchao,SUN Changyu.Recognition of adsorption/desorption theory in coalbed methane reservoir and shale gas reservoir[J].Acta Petrolei Sinica,2014,35(6):1113-1129.