A new hole cleaning method by using hydraulic jet for plugged drainage boreholes in soft coal seams

作者：Lyu Youchang; Kou Jianxin; Zhou Zhe^*

来源：Electronic Journal of Geotechnical Engineering, 2016, 21(14): 4745-4758.

• CBM extractions
• Cbm productions
• Extraction efficiencies
• Hole cleaning
• Laboratory experiments
• Plugging problems
• Safety production
• Single hole

The coal bed methane (CBM) drainage boreholes in soft coal seams are easy to collapse and have problems of plugged boreholes. The CBM extraction ability of plugged borehole is very low, and the extraction amount and concentration is almost zero when the plugging problems are serious. The plugging problems can affect the CBM production seriously, and threaten the safety production of coal mines. To solve above problems, this paper proposes a new method of using hydraulic jet self-propelled bit to break down the plugged sections of boreholes in order to improve the CBM extraction efficiency. Based on the theoretical analysis on the reasons of borehole collapse and the hole cleaning principle of hydraulic jet self-propelled bit, the laboratory experiments were conducted to optimize hole cleaning parameters, and the field tests were carried out in Pingdingshan No.12 mine. After the implementation of hole cleaning, the CBM daily extraction amount of single-hole increased from the original 101m3/d to 247m3/d~435m3/d, and the extraction concentration of single-hole increased from 5% to 47%~92%, significantly increasing the extraction efficiency. The experimental results show that using hydraulic jet self-propelled bit can effectively dredge the plugged drainage boreholes.

• 出版日期2016