Methods and Apparatus for Wireline Drilling On Coiled Tubing

Abstract

Apparatus for drilling an underground borehole, comprising:a tubular conveyance system (18) including an electric cable and a supply of drilling fluid, the supply of drilling fluid being arranged in use to pump fluid from the surface down the inside of the tubular conveyance so as to return to the surface via the annulus between the outside of the tubular conveyance and the borehole;a drilling system comprising an electrically powered pump and a drilling motor, the pump being arranged in use to pump fluid from the borehole outside the drilling system up through the inside of the drilling system;a connector connecting the drilling system to the tubular conveyance system (18), through which the pump and motor are connected to the electric cable, anda flow diverter at which flow down the inside of the tubular conveyance system (18) is diverted into the annulus, and flow up the inside of the drilling system is diverted into the annulus.

Description

TECHNICAL FIELD [0001]This invention relates to methods and apparatus for drilling boreholes that is particularly applicable to drilling with wireline drilling apparatus carried on coiled tubing.BACKGROUND ART [0002]Current conventional coiled tubing drilling (CTD) employs high hydraulic power delivered from the surface through the coiled tubing (CT) to power a drilling positive displacement motor (PDM) that in turn powers the drill bit. This high drilling power requires a large-diameter CT that demands larger surface installations.[0003]Current methods of changing the trajectory in CTD typically involve a fixed bend on the PDM, and a hydraulic or electric-over-hydraulic means of rotating the bend azimuth. Apart from the larger and heavier surface equipment, this way of drilling on CT is limited in reach by the buckling limit of the CT, and involves a low-efficiency conversion of hydraulic power to drilling footage.[0004]U.S. Pat. No. 2,548,616 describes a method of drilling a well ...

AI Technical Summary

Benefits of technology

[0015]The use of the flow diverter makes it possible to provide reverse circulation (circulation of fluid from the annulus into the BHA) where drilling is taking place, so improving hole cleaning in small diameter boreholes and reducing the risk of sticking.

[0019]In use, the flow diverter can direct part of the drilling fluid down around the outside of the drilling system and the remainder of the fluid back to the surface around the outside of the tubular conveyance. Thus the reverse circulation around the drilling system changes to conventional circulation around the tubular conveyance which allows improved cuttings transport in the main part of the borehole. The flow diverter can be arranged to divert flow from the inside of the drilling system to the annulus above the point at which it diverts flow from the tubular conveyance system into the annulus.

Problems solved by technology

This high drilling power requires a large-diameter CT that demands larger surface installations.

Apart from the larger and heavier surface equipment, this way of drilling on CT is limited in reach by the buckling limit of the CT, and involves a low-efficiency conversion of hydraulic power to drilling footage.

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