Patent ID: 7108080
Filing Date: 2006-09-19
Classification: E21B

Abstract:
1. A borehole drilling apparatus comprising: a drill string including a center bore and a distal end; a bit assembly at the drill string's distal end; a ported sub mounted on the drill string, the ported sub including an upper surface, a lower surface, a bore extending from the upper surface to the lower surface to which the drill string is connected, an axially extending port for providing fluid communication between the lower surface and the upper surface separate from fluid communication with the bore and a lateral port for providing fluid communication between the drill string center bore and an outer surface of the sub between the upper surface and the lower surface, the lateral port being substantially isolated against fluid communication with the axially extending port during operation; and a liner engaging surface encircling the lower surface, the liner engaging surface formed to releasably secure a borehole liner such that the drill string extends through the borehole liner with the bit assembly extending beyond a liner shoe of the liner with an opening between the drill string and the liner.