基于实时核磁共振的煤岩气驱水流动特性试验研究  

Experimental study on flow characteristics of gas flooding water in coal by real-time nuclear magnetic resonance

作　　者：葛兆龙[1,2] 王浩明 周哲[1,2] 卢义玉[1,2] 高飞飞 GE Zhaolong;WANG Haoming;ZHOU Zhe;LU Yiyu;GAO Feifei(State Key Laboratory for Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqingg 400044,China;State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam,Chongqing University,Chongqing 400044,China)

机构地区：[1]重庆大学煤矿灾害动力学与控制国家重点实验室,重庆400044 [2]重庆大学复杂煤层气瓦斯抽采国家地方联合工程实验室,重庆400044

出　　处：《采矿与安全工程学报》2023年第1期194-203,共10页Journal of Mining & Safety Engineering

基　　金：国家自然科学基金项目(51804050);重庆市自然科学基金项目(cstc2019jcyj-bshX0041);全职博士后出站留(来)渝项目(2020LY15)。

摘　　要：煤层气排采过程中,气水两相流阶段极易产生储层伤害,正确认识气水产出机理对高效开发煤层气具有重要意义。本文利用核磁共振技术,基于CPMG回波序列法,实时测试煤岩不同围压条件下饱水及氮气驱水过程中的横向弛豫时间,结合分形理论分析煤岩气驱水过程中围压及驱替压力对气水运移路径的影响,研究煤岩气液两相微观流动特征。结果表明:在饱水条件下,随着围压的增加,煤基质在围压与孔隙水压的共同作用下发生摩擦挤压作用,导致大孔明显减少,而微孔及中孔增加;气驱水过程中,气体会优先占据大孔中央,高围压会对煤岩产生不可逆的损伤,含水饱和度的降低主要发生在运移孔中,残余水主要分布在煤岩狭小喉道和孔隙盲端及被狭小喉道连通的大孔中。该研究对加深煤层气水产出机理的认识及煤层气开发排采技术选择具有重要意义。In the process of coalbed methane drainage,the gas-water two-phase flow stage is very easy to cause reservoir damage.Correctly understand of the mechanism of the gas-water production is a great significance for the efficient development of coalbed methane.In this work,based on CPMG echo sequence method,the lateral relaxation time of coal during the process of water saturation and nitrogen flooding under different confining pressures was measured in real time by nuclear magnetic resonance technology.Moreover,the effects of confining pressure and displacement pressure on the evolution of pore structure were analyzed by combining the fractal theory.The experiments of micro seepage of gas-liquid two-phase flow in coal were carried out.The results indicate that frictional extrusion of coal matrix occurred duo to the interaction of confining pressure and pore water pressure.Further,the frictional extrusion caused porosity of large pore decrease,and micro pore and middle size pore increased with the increase of the confining pressure during the process of flooding.Gas would preferentially occupy the center of large pores and the coal would be irreversibly damaged under high confining pressure during the process of nitrogen flooding.In addition,the migration pores make a great deal of contribution to the decrease of water saturation.Residual water is mainly distributed in the narrow throats dead-end pores and the large pores connected by the narrow throats.This work has a great significance to comprehend mechanism of the gas-liquid two-phase seepage in coal and to select the coalbed methane development technology.

关 键 词：实时核磁共振 气驱水 围压 微观渗流 

分 类 号：TD981[矿业工程—选矿]