| 摘要 |
<p>K 9647 A B S T A C T METHOD OF DRILLING A BOREHOLE A method of drilling a borehole is provided using a drill bit coupled to the lower end of a pair of concentric drill pipes. During drilling a first low-viscosity fluid, such as oil or water, is circulated through the pipes while a second fluid, such as a weighted viscosified mud, is kept stationary in the pipe-formation annulus. DZRH04</p> |
