Northeast Permafrost Gas Hydrate Scientific Drilling Test And The Analysis of Factors Influencing Drilling Efficiency

In the Northeast permafrost zone of China,MK-2 hole was drilled for natural gas hydrate drilling test by using gas hydrate coring technology and drilling parameter monitoring system.Drilling parameter monitoring system can collect parameters such as depth,WOB,ROP,rotary speed,rotary torque,flow rate and mud pump pressure.Combining with these parameters and the formation conditions,the factors that affect the drilling efficiency were analyzed.By the analysis,some results are gotten: ①low drilling efficiency is in the broken belt,carbonaceous slate and mylonite formation;while high drilling efficiency in sandstone,sandy shale and slate;②obtaining the optimal WOB for different strata;③test technology,equipment and test results in the MK-2 hole can be reference for future natural gas hydrate drilling.