Systems and methods for drilling boreholes with noncircular or variable cross-sections

摘要

In a pulsed-electric drilling system, a nonrotating bit is given a noncircular shape to drill a correspondingly-shaped borehole, e.g., triangular, rectangular, polygonal, oval, or a more complex shape. Some embodiments employ a reconfigurable bit that deploys extensions as needed to dynamically vary the cross-section of the borehole at selected locations. In this fashion, a driller is able to create borehole with a preferred cross-sectional shape to, e.g., drill the smallest possible hole while simultaneously providing additional clearance for equipment or instrumentation, additional surface area for well inflow, channels for improved borehole cleaning, teeth for improved cementing, reduced contact area to reduce drag on the drillstring, or any other benefits achievable by customizing the borehole cross-section.

主权项

1. A method for drilling a noncircular earth borehole, the method comprising:
maintaining a bit in position at a bottom of the noncircular earth borehole without rotating said bit through more than 60° per inch of forward progress, said bit having a noncircular transverse cross-section; detaching material from the bottom of the noncircular earth borehole with pulses of electrical current; and flushing detached material from the noncircular earth borehole with a flow of drilling fluid.