摘要
碳酸盐矿物与页岩气储层的孔隙结构密切相关,探讨二者之间的定量关系有助于深化对页岩岩石学定量表征与微米/纳米尺度孔隙改造等的认识。为此选取四川盆地东部彭水地区下志留统龙马溪组页岩,开展了稀盐酸—页岩酸岩反应实验;综合利用场发射电镜、微CT以及低压氮气吸附方法,表征溶蚀前后孔隙结构;研究碳酸盐矿物对页岩储层孔隙结构的影响,进而探讨溶蚀孔的地质、工程指示意义。研究结果表明:①常温下酸岩反应120 h,碳酸盐矿物完全溶蚀而其他矿物则无明显变化;②碳酸盐矿物完全溶蚀后,出现大量孔径介于3.9~62.5μm的溶蚀孔,溶蚀孔总体积分数占比为6.8%,与样品酸溶率数值6.9%接近,同时纳米孔的形态、体积、孔径、表面积等参数未发生明显的变化;③碳酸盐矿物完全酸溶后仅产生微米孔,而在纳米尺度未表现出增孔、扩孔现象,表明碳酸盐晶粒处于微米尺度。结论认为,基于微米级溶蚀孔的图像统计参数,可以有效反演碳酸盐矿物的微观分布、形貌、数量、粒径等特征参数,为页岩岩石学定量研究提供了一种新的方法,同时该溶蚀孔协同水力压裂缝网,有助于加速页岩气的产出。
Carbonate minerals are closely related to pore structures in shale gas reservoirs,and the discussion on their quantitative relationship is conducive to deepening the quantitative characterization of shale petrology and the understanding on pore transformation in the micrometer/nanometer scale.In this paper,the shale of Lower Silurian Longmaxi Formation in the Pengshui area of the eastern Sichuan Basin was selected to perform dilute hydrochloric acid-shale reaction experiment.Then,the pore structures before and after the dissolution were characterized by means of field-emission scanning electron microscopy,micro-CT and low-pressure nitrogen adsorption comprehensively.The influence of carbonate minerals on the pore structures in shale gas reservoirs was studied.Finally,the geological and engineering indicating significance of dissolution pores was discussed.And the following research results were obtained.First,after 120 hours of acid-rock reaction under room temperature,carbonate minerals are completely dissolved while the other minerals don’t change obviously.Second,after carbonate minerals are completely dissolved,a large number of dissolution pores with a diameter of 3.9-62.5μm appear and their total volume fraction percentage is 6.8%,which is close to the acid-induced dissolution rate of the sample,6.9%.Besides,the shape,volume,pore size,surface area and other parameters of nanopores do not change significantly.Third,after carbonate minerals are dissolved completely by acid,only micropores are generated and the phenomenon of pore increase and enlargement does not occur in the nanometer scale,indicating that the carbonate crystal grains are in a micrometer scale.In conclusion,the image statistical parameters of micro-scale dissolution pores can effectively invert the characteristic parameters of carbonate minerals(such as microscopic distribution,morphology,quantity and particle size)and provides a new method for the quantitative research of shale petrology.In addition,dissolution pores,together with hydraul
作者
梁运培
陈强
廖志伟
林丹
LIANG Yunpei;CHEN Qiang;LIAO Zhiwei;LIN Dan(State Key Laboratory of Coal Mine Disaster Dynamics and Control//Chongqing University,Chongqing 400044,China;School of Resources and Safety Engineering,Chongqing University,Chongqing 400044,China;Chengdu University,Chengdu,Sichuan 610106,China)
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2021年第1期93-101,共9页
Natural Gas Industry
基金
国家自然科学基金青年科学基金项目“下扬子深水相大隆组黑色岩系对晚二叠世末大洋缺氧事件的响应及其油气地质意义”(编号:41702129)
中国博士后科学基金面上项目“热冲击下页岩纳米孔水热增压及其致裂增渗机理研究”(编号:2020M683248)
重庆市教委科学技术研究项目“重庆地区奥陶纪—志留纪之交沉积环境演化及其对页岩气勘探的启示”(编号:KJQN201800115)。
关键词
碳酸盐矿物
溶蚀改造作用
页岩储集层
孔隙结构
酸岩反应
溶蚀孔
四川盆地东部
下志留统龙马溪组
Carbonate mineral
Dissolution
Shale reservoir
Pore structure
Acid-rock reaction
Dissolution pore
Eastern Sichuan Basin
Lower Silurian Longmaxi Formation
