| 摘要 |
<p>Method and apparatus for drilling a well bore in a hydrocarbon formation using concentric drill string (4) having an inner pipe (6) and an outer pipe (12) defining an annulus there between. A drilling means such as an air hammer or a rotary drill bit and driving system is provide at the lower end of the concentric drill string and drilling medium (76) is delivered through the annulus or inner pipe for operating the drilling means to form a borehole. Drilling medium, drilling cutting and hydrocarbon are removed from the well bore by extracting the drilling medium, drilling cutting and hydrocarbon through the other of the annulus or inner pipe.</p> |
