摘要
煤层气吸附/解吸特征、渗流机理和排采控制是煤层气井生产的重要因素。为此,进行了煤层气吸附解吸实验和渗流特征实验,结果表明:煤层气吸附/解吸是可逆的,存在"解吸滞后现象";煤层气渗流呈现二级渗流特征,即煤的基质孔隙内流体的渗流呈非达西渗流和天然裂隙及大孔隙内流体的渗流呈达西渗流;煤层气排采过程中,随着排水降压,规模开发可导致"气水分异",局部高点气产量高、水产量低,相对低点产水量高、产气量低。同时,煤层气井排采过快、洗井修井、停抽关井、液面低于煤层顶面等易造成污染,致使气水产量锐减,其伤害机理主要是煤粉堵塞伤害、应力敏感伤害和气锁/水锁伤害。基于伤害特点及伤害机理,结合多年的排采经验,确立了以定压排采、控制合理工作压差和控制煤粉适度产出等排采工作制度。
The characteristics of adsorption /desorption of coal-bed methane,percolation mechanism and drainage control are important factors in the process of CBM production. The experiments on adsorption /desorption of CBM and characteristics of percolation were carried out in this study. The results show that the process of adsorption /desorption of CBM is reversible,while the 'desorption hysteresis'occurs in the process. The seepage of CBM presents the characteristics of secondary percolation,which means that the seepage flow in coal matrix porosity is non-Darcy flow and the flow in natural fractures and large pore is Darcy flow. In addition,the study has found a phenomenon of'gas-water difference'in coal seams at a large scale development for the drainage decompression in the process of gas recovery.The gas yield is high with low water production at local high locations,while the water yield is high with low gas production at relatively low locations. At the same time,the damage process includes fast production,work over,stop pumping and shut-in and low fluid level below the top surface of coal seam can easily lead to pollutions which result in the sharp decrease of gas-water production. Its damage mechanism mainly includes pulverized coal jam damage,stress sensitivity damage,air lock damage and water lock damage. Based on the damage characteristics,damage mechanisms andmany years' practical experience on CBM production,a drainage working system has been developed including draining with constant pressure,controlling a reasonable working pressure difference and maintaining a sound pulverized coal production rate.
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2014年第9期1927-1931,共5页
Journal of China Coal Society
基金
国家科技重大专项资助项目(2011ZX05034-003
2011ZX05042-001
2011ZX05063)
关键词
煤层气
产气机理
控压
控粉
排采
coal-bed methane
CBM production mechanism
bottom-hole pressure
coal fines
production
