Application of self-advanced water jet drilling technology in coalbed methane exploration

Self-advanced high pressure water jet drilling technology is to use mechanical or water jet apparatus to form a cavity at the selected coal seam,a specially made whip-stock is then to be installed in the cavity to drill inseam horizontal holes from the vertical well.A self-advanced drilling head consists of spinning jet nozzles,cutting treatment apparatus and thrust providing apparatus etc.The drilling head drags the high pressure water hose to form holes continuously.High pressure water flows through the hose to provide drilling power and propelling thrust as well as flush coal cuttings out of the well.Using this technology can bore a number of radial holes at different coal seams from the single well.As the horizontal inseam holes form new methane flow passages,the space of vertical wells can be significantly increased by drilling these radial boreholes thus dramatically increases the methane production.