摘要
为更好表征页岩孔隙结构的非均质性以及明确非均质性对页岩气富集影响作用,文中选取40块威远地区下志留统龙马溪组井下样品进行TOC,XRD衍射、低温氮气吸附以及甲烷等温吸附等一系列分析测试.从孔隙结构和矿物成分两个层次探讨了页岩分形维数的影响因素,认为页岩的分形维数受微孔发育影响.研究结果表明:页岩非均质性很强,下志留统龙马溪组龙一1亚段的1~4小层的TOC、矿物成分、孔隙度均存在较大差异,其中1小层中下部TOC、石英含量以及孔隙度值都较高.基于氮气吸附测试,采用FHH模型计算了页岩分形维数,计算结果表明页岩的分形维数介于2.590~2.750,平均值为2.670,其中1小层中下部分形维数最高,其次为3小层,2、4小层及1小层上部分形维数较小.TOC与生物石英含量控制了微孔的发育,因此高TOC与高石英含量均导致页岩分形维数增大;黏土、碳酸盐岩以及长石由于主体发育大孔,使得页岩孔径增大,故其含量的增加会导致页岩分形维数减小.1小层中下部由于具有丰富的气体物质来源(TOC)、储集空间以及保存条件(分形维数大,气体扩散解吸渗流困难)导致在1小层中下部页岩气含气量最高,另外由于脆性矿物含量高,利于压裂形成缝网,因此1小层中下部为最有利的页岩气甜点段.
In order to better characterize the heterogeneity of the shale pore structure and figure out its effect on shale gas enrichment,40 samples from the Lower Silurian Longmaxi formation in Weiyuan shale gas field were selected,and a series of experiments including TOC content,XRD mineral composition,low-pressure nitrogen adsorption(LPNA)and high-pressure methane sorption were conducted.The factors influencing the fractal dimension of shale are discussed from two aspects,namely the pore structure and mineral composition,and it is believed that the fractal dimension of shale is affected by the development of micropores.The experimental results show that the shale heterogeneity is very strong.The TOC,mineral composition and porosity of the four sublayers in the Longmaxi Formation vary greatly.And the reservoir parameters of TOC,quartz content,and porosity have the highest value in the middle and lower parts of the first sublayer(Long1■).Based on the results of LPNA,the fractal dimension of shale was calculated by FHH model.The fractal dimension of shale ranges from 2.590 to 2.750,with an average of 2.670.The middle and lower parts of Long1■have the highest fractal dimension,followed by Long1■,Long1■,and Long1■,while the upper part of Long1■has a smaller fractal dimension.The contents of TOC and bio-quartz control the development of micropores,so both high TOC content and high quartz content could lead to an increase in fractal dimensions of shale.Since the development of large pores in clay,carbonate and feldspar minerals can lead to the increase of the pore size of shale,the increase in their contents will result in a decrease in fractal dimensions of shale.The middle and lower parts of Long1■are rich in gas generation material(TOC),enough storage space,and good preservation conditions(large in the fractal dimension,difficult in the gas diffusion,desorption,and seepage),leading to the highest gas content of shale in those intervals.In addition,the high brittle mineral content in those intervals is conducive to fracturing and the formation of a fracture network.Therefore,the middle and lower parts of Long1■are the most favorable sweet spots for shale gas development.
作者
张琴
梁峰
梁萍萍
周尚文
郭为
郭伟
卢斌
刘卫红
ZHANG Qin;LIANG Feng;LIANG Pingping;ZHOU Shangwen;GUO Wei;GUO Wei;LU Bin;LIU Weihong(PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China;National Energy Shale Gas R&D(Experimental)Center,Langfang,Hebei 065007,China)
出处
《中国矿业大学学报》
EI
CAS
CSCD
北大核心
2020年第1期110-122,共13页
Journal of China University of Mining & Technology
基金
国家油气重大专项(2017ZX05035).
关键词
龙马溪组页岩
非均质性
分形特征
主控因素
威远页岩气田
Longmaxi shale
heterogeneity
fractal characteristics
main controlling factors
Weiyuan shale gas field
