Application of slimpulse MWD instruments in buried-hill aerated underbalanced drilling

During aerated unbalance drilling process, if the liquid-gas ratio is beyond some value in drill pipes, conventional slurry pulse MWD signal intense decreases fast, leading to inaccuracy data transmitting. So the issue of wellbore trajectory control in underbalanced drilling section limits the development of MWD and its application. Through the survey on various MWD instruments in China and abroad, Slimpulse MWD instrument is selected to conduct the function. The article analyzed the reason affecting the MWD pulse signal in aerated unbalance drilling process, proposed the principle of optimizing MWD instrument in aerated drilling high-temperature deep buried-hill formations, and briefly introduced the principle of slimpulse instrument from Schlumburger. It also made a point that the instrument could meet the normal orientation inclinometer requirements. Through the successful applications on the Well NP1-83, NP1-88, sidetracked NP1-88 and so on, it achieved trajectory control in high-temperature buried-hill aerated underbalanced drilling.