METHOD AND APPARATUS FOR DRILLING A BOREHOLE WITH A BOREHOLE LINER

摘要

A method for drilling a borehole includes; providing a drill string (10) of drill pipe including a center bore (13), a distal end, a bit assembly (15) at the distal end; hanging a liner (18) from the drill string (10), thereby forming an annular space between the drill string (10) and the liner (18) and with the bit assembly (15) extending from a lower end of the liner (18); positioning the drill string (10) with the liner (18) attached thereto in a borehole such that a second annular space (21) is formed between the liner and the borehole wall; operating the bit assembly (15) to proceed with drilling the borehole; and circulating drilling fluid down through the center bore (13) of the drill string out through the bit assembly and down through the second annular space (21) between the liner and the borehole wall, the drilling fluid returning up through the annular space between the drill string and the liner. An apparatus for use in this method is also disclosed.