Expandable reamer for drilling subterranean formation has blades carried by tubular body and each carrying cutting structure(s), blade biasing element, structure to retain movable blade at outermost lateral position, and actuation device

Expandable reamer for drilling a subterranean formation comprises blades carried by a tubular body and each carrying cutting structure(s), a blade biasing element to hold a laterally movable blade at an innermost lateral position corresponding to an initial diameter of the reamer, a structure for retaining the movable blade at an outermost lateral position corresponding to an expanded diameter of the reamer, and an actuation device. Expandable reamer for drilling a subterranean formation comprises a tubular body (532) having a longitudinal axis (525) and a leading end for connecting to a pilot drill bit and a trailing end for connecting to a drill string, a drilling fluid flow path extending through the expandable reamer for conducting drilling fluid through it, radially and longitudinally extending blades (512, 514) carried by the tubular body and each carrying at least one cutting structure (536), a blade biasing element for holding a laterally movable blade at an innermost lateral position corresponding to no more than an initial diameter of the reamer with a force, a structure (516, 520) for retaining the laterally movable blade at an outermost lateral position corresponding to an expanded diameter of the reamer, and an actuation device positioned along an inner diameter of the tubular body and configured to selectively prevent or allow drilling fluid communication with the laterally movable blade according to a flow rate of drilling fluid passing through it. An independent claim is also included for a method of reaming a borehole in a subterranean formation, which comprises disposing an expandable reamer apparatus within the subterranean formation, biasing the laterally movable blade to a laterally innermost position corresponding to an initial diameter of the reamer, flowing drilling fluid through the reamer via a drilling fluid flow path while preventing drilling fluid from communicating with the movable blade, allowing drilling fluid to communicate with the movable blade, causing the movable blade to move to an outermost lateral position, and reaming a borehole in a subterranean formation by rotation and displacement of the reamer within the subterranean formation. Elargisseur expansible pour forer une formation souterraine, comprenant un corps tubulaire, un trajet d'écoulement de fluide de forage s'étendant à travers l'élargisseur pour guider du fluide de forage au travers, une pluralité de lames qui s'étendent radicalement et longitudinalement da