Abstract: An apparatus for creating pressure pulses in the fluid of a bore hole is described. The preferred embodiment takes the form of a mud pulser apparatus having a signalling valve controlled by a variable pilot valve. The forces on the signalling valve are balanced and controlled by the flow of mud through the variable orifice of the pilot valve. The arrangement is such as to act like a hydraulic amplifier, and results in the signalling valve being compensated for variable flow rates. In the preferred embodiment, the pilot valve has rotary vanes that allow it to be self-cleaning.

Abstract: A modulator is disclosed for creating a pressure pulse in a fluid-filled well. The modulator comprises a tool body on which a plurality of extendable arms are mounted. The arms may be retracted into a stowed position substantially adjacent the tool body, or may be extended to meet the wall of the borehole. The arms are preferably resilient bowsprings that may be flexed outwards from the tool by means of an actuator pushing on at least one end of the springs. A flexible valve sleeve or bag is suspended between the arms and cooperates with a valve mounted adjacent the sleeve on the tool body. The valve sleeve creates a fluid-flow path through the valve, and in operation, the valve closes one end of the valve sleeve to create the pressure pulse. Sealing of the valve sleeve against the wall of the well is a result of the fluid pressure inflating the sleeve against the well wall. As a result, sealing takes place over an extended area of the bag and is dynamically responsive to changes in fluid flow or pressure.

Abstract: An apparatus for creating pressure pulses in the fluid of a bore hole is described. The preferred embodiment takes the form of a mud pulser apparatus (10) having a signalling valve controlled by a variable pilot valve (34). The forces on the signalling valve are balanced and controlled by the flow of mud through the variable orifice of the pilot valve. The arrangement is such as to act like a hydraulic amplifier, and results in the signalling valve being compensated for variable flow rates. In the preferred embodiment, the pilot valve has rotary vanes that allow it to be self-cleaning.

Abstract: A modulator is disclosed for creating a pressure pulse in a fluid-filled well. The modulator comprises a tool body on which a plurality of extendable arms are mounted. The arms may be retracted into a stowed position substantially adjacent the tool body, or may be extended to meet the wall of the borehole. The arms are preferably resilient bowsprings that may be flexed outwards from the tool by means of an actuator pushing on at least one end of the springs. A flexible valve sleeve or bag is suspended between the arms and cooperates with a valve mounted adjacent the sleeve on the tool body. The valve sleeve creates a fluid-flow path through the valve, and in operation, the valve closes one end of the valve sleeve to create the pressure pulse. Sealing of the valve sleeve against the wall of the well is a result of the fluid pressure inflating the sleeve against the well wall. As a result, sealing takes place over an extended area of the bag and is dynamically responsive to changes in fluid flow or pressure.

Abstract: A shock absorbing tool for use in pipelines and oil wells, particularly in combination with perforation guns comprises a central mass supported on two springs between the end terminal members. The shock wave is absorbed in the free oscillation of the mass. The mass is constituted by a piston assembly. A steel rope permits the shock absorbing tool to be maneuvered within the bore hole without damage to the springs.

Abstract: A tubular cutting tool includes two or more sets of electrically actuated retractable anchoring legs mounted at longitudinally spaced apart locations and an electrically driven rotary cutting head with a retractable cutting blade. The anchoring legs can be arranged such that they are capable of compensating for variations in the internal radii of the tubular to be cut, thereby ensuring that the cutting tool is clamped rigidly in position.

Abstract: A method and apparatus for measuring the properties such as permeability of the rock surrounding a borehole in which a directional seismic or sonic signal is generated downhole and propagated into the surrounding formation to generate an electrokinetic signal and the focus of the seismic signal is moved in three dimensions in the surrounding rock by physically moving the source or by having two seismic sources which generate oscillating seismic signals at different frequencies and the focus of the seismic signal is varied by wave interference or wave interaction.

Abstract: A shock absorbing tool for use in pipelines and oil wells, particularly in combination with perforation guns comprises a central mass supported on two springs between the end terminal members. The shock wave is absorbed in the free oscillation of the mass. The mass is constituted by a piston assembly. A steel rope permits the shock absorbing tool to be maneuvered within the bore hole without damage to the springs.

Abstract: A device for measuring the rate of flow of fluids in a conduit is positioned within the conduit and includes a tube having two spaced part detectors which are separated by shielding units either side of them which are not in electrical contact with the detector units, when a variable electrical field is applied between the walls of the conduit and the shielding units the detector units detect discontinuities in the fluid, e.g., by detecting changes in the ratio of voltage to current and by correlating the movement of the discontinuities between the detector units, it is possible to measure the rate of flow of the fluid.

Abstract: A tubular cutting tool includes two or more sets of electrically actuated retractable anchoring legs (52,54) mounted at longitudinally spaced apart locations and an electrically driven rotary cutting head (14) with a retractable cutting blade (14). The anchoring legs can be arranged such that they are capable of compensating for variations in the internal radii of the tubular to be cut, thereby ensuring that the cutting tool is clamped rigidly in position.

Abstract: A fluid density measurement device includes a float (12) and a weight (14), each mounted on links (16) for essentially vertical movement. A crank (22) is mounted above the float and weight and is connected to them,by a float link (24) and a counterweight link (28) to convert the forces from the float and the forces from the weight to rotational forces on the crank acting in opposite directions. The position adopted by the crank will be dependent upon the density of the fluid in which the instrument is immersed. The links (16) are arranged so that a good approximation to straight line motion is obtained at the centre of the float and the weight.