Abstract: A well tool apparatus comprises a control arrangement configured to control response of the downhole tool by varying a bore-annulus pressure difference. The control arrangement includes a valve piston longitudinally slidable in a generally tubular controller housing that is in operation substantially co-axial with the wellbore, to open or close a valve port to a fluid flow connection between the drill strings interior and the tool. A latch mechanism is configured to latch the valve piston against movement in one axial direction, keeping the valve piston in an open or a closed condition. Unlatching of the valve piston requires displacement thereof in the other axial direction to a mode change position. A stay member is automatically displaceable under hydraulic actuation responsive to bore-annulus pressure differences above a trigger threshold value, to obstruct movement of the latched valve piston under hydraulic actuation to the mode change position.

Abstract: A well tool apparatus comprises a control arrangement configured to control response of the downhole tool by varying a bore-annulus pressure difference. The control arrangement includes a valve piston longitudinally slidable in a generally tubular controller housing that is in operation substantially co-axial with the wellbore, to open or close a valve port to a fluid flow connection between the drill strings interior and the tool. A latch mechanism is configured to latch the valve piston against movement in one axial direction, keeping the valve piston in an open or a closed condition. Unlatching of the valve piston requires displacement thereof in the other axial direction to a mode change position. A stay member is automatically displaceable under hydraulic actuation responsive to bore-annulus pressure differences above a trigger threshold value, to obstruct movement of the latched valve piston under hydraulic actuation to the mode change position.

Abstract: A seal assembly for a reamer tool positionable in a wellbore includes an annular seal disposed in a longitudinal bore of a tool housing of the reamer tool; an annular wiper disposed upstream of the annular seal in the longitudinal bore; and a tubular sleeve coupled to and movable with a drive mechanism disposed in the longitudinal bore of the tool housing. The tubular sleeve is disposed in a radial gap between the drive mechanism and a surface of the longitudinal bore of the tool housing. The sleeve includes a radial opening through a sidewall of the sleeve, and the tubular sleeve is slidably engageable with the annular seal and with the annular wiper as the drive mechanism is moved through the longitudinal bore of the tool housing.

Abstract: Systems and methods for drilling operations may use encapsulated explosives to complement the performance of downhole cutting tools. An exemplary method may include drilling a wellbore penetrating a subterranean formation with a downhole cutting tool; circulating a drilling fluid in the wellbore, wherein the drilling fluid comprises a base fluid and an encapsulated explosive having an average diameter of about 10 nm to about 20 microns; triggering detonation of the encapsulated explosive; and detonating the encapsulated explosive proximal to a portion of the subterranean formation adjacent the downhole cutting tool.