Die Erfindung betrifft ein Verfahren zur Energieversorgung von Meß- und/oder Steuereinrichtungen im Bereich des Bohrkopfes von Vortriebsmaschinen für Bohrungen. insbesondere Horizontalbohrungen sowie eine Vortriebsmaschine mit einer Einrichtung zur Durchführung dieses Verfahrens. Um Zuleitungen zum Schneidschuh (3) zu vermeiden und somit die Manipulation während der Bohrung zu erleichtern, ist vorgesehen, daß die Meß- und/oder Steuereinrichtungen über die Drehung einer Förderschnecke (2) angetrieben werden. Eine Vortriebsmaschine mit einem lenkbaren Schneidschuh (3) und einer in einem Schutzrohr (6) drehbar angeordneten Förderschnecke (2) sieht vor, daß zwischen der Förderschnecke (2) und dem Schutzrohr (6) ein Zahnrad (10) od. dgl. angeordnet ist. welches über die Drehung der Förderschnecke (2) antreibbar ist. Die Übertragung der Drehung der Förderschnecke (2) auf das Zahnrad (10) kann beispielsweise durch eine an der Förderschnecke (2) angeordnete Leiste (7) gebildet sein, welche einen mit einem Zahnkranz (9) verbundenen Mitnehmer (8) mitnimmt, wobei über den Zahnkranz (9) das Zahnrad (10) antreibbar ist.

A system for controlling the rotation of a roll stabilisable control unit in a steerable rotary drilling assembly comprises an instrument carrier (24) rotatably mounted on a support (23) connected to the drill string. A first rotatable impeller (28) is mounted for rotation by a flow of drilling fluid over the impeller and is coupled to the instrument carrier (24) so as to transmit a torque to it. Sensors (27) carried by the instrument carrier sense the rotational orientation of the instrument carrier and produce a control signal indicative of its rotational orientation, and the torque applied to the instrument carrier by the impeller (28) is controlled, at least partly in response to said signal, so that the instrument carrier can, for example, be roll stabilised if required. A second rotatable impeller (38) is coupled to the instrument carrier for transmitting to it a second torque, which may also be controlled, in the opposite direction to the torque transmitted by the first impeller (28). The provision of two opposed impellers allows the rotation of the control unit to be controlled over a greater range than is possible with a single impeller.

A steerable rotary drilling system includes a roll stabilised instrument assembly (12) having an output control shaft (85), the rotational orientation of which represents a desired direction of steering. The control shaft is coupled to a bottom hole assembly which includes a drill bit 50 and a synchronous modulated bias unit including means (59,60,61,62) for applying a lateral displacement to the drill bit. Rotation of the bias unit relatively to the control shaft (85) modulates the lateral displacement in synchronism with rotation of the drill bit, and in a phase relation thereto determined by the rotational orientation of the control shaft, so that the maximum lateral displacement is applied to the bit at a rotational orientation thereof which is dependent on the rotational orientation of the control shaft, thereby causing the bit to become displaced laterally in the desired direction as drilling continues. Means (86) are provided for decoupling the control shaft (85) from the bias unit while maintaining the integrity of both the roll stabilised assembly and the bias unit.

A measuring tool for collecting down hole information, which essentially has a sensor sub including plural data collecting sensors secured at a forward portion of a drilling pipe and a sonde movable in the drilling pipe. Both the sensor sub and sonde employ a set of loop antennas to effect radiocommunication between them to thereby certainly send data detected by means of the sensors to the sonde. A metering valve for producing mud-pulse used in the measuring tool, wherein there is provided a changeover means switching the main mud-flow stream from one of the detour/interference passages and the straight/open passage to the other.

A downhole electrical power supply apparatus has a high fluid pressure source zone (102) and a low fluid pressure discharge zone (104) each defined at least partially within the apparatus. A fluid powered engine (106) provides rotational mechanical output and is powered by fluid flowing from the source zone (102) through the engine (106) to the discharge zone (104). An electrical generator (118) converts the rotational mechanical output of the engine into electrical output power supply.

A downhole electrical power supply apparatus has a high fluid pressure source zone (102) and a low fluid pressure discharge zone (104) each defined at least partially within the apparatus. A fluid powered engine (106) provides rotational mechanical output and is powered by fluid flowing from the source zone (102) through the engine (106) to the discharge zone (104). An electrical generator (118) converts the rotational mechanical output of the engine into electrical output power supply.

An adjustable drill string stabiliser has a plurality of fins (232) biased inwardly and movable outwardly by follower portions (234A, 234B) bearing on a cam surface (205). The cam surfaces (205) for the several fins (232) are formed in a non-uniform manner to provide control enabling the fins to project from the stabiliser by different amounts.

0 A downhole tool for an oil or gas well includes a self-contained power supply having a housing (6) in which a primary fuel source (18), a Stirling cycle engine (20), and a linear alternator (22) are disposed. The primary fuel source includes a radioisotope which, by its radioactive decay, provides heat to operate the Stirling engine which in turn drives the linear alternator to provide a suitable electrical output for us by the circuit of the downhole tool.

The invention relates to a means for generating electric energy in a borehole during drilling thereof, which means comprises a housing (30) having connector means (33, 34) at the ends thereof for inserting the housing (30) in a drill string. The housing (30) includes a conduit system (130) for passing fluid through the housing (30) a valve (111, 131) located in the conduit system (30) and an electric generator (110). The electric generator (110) consists of a stator (114) and an anchor (112). The stator (114) is mounted immovably in the housing (30) and the anchor (112) is mounted such that it can move in a reciprocating mode relative to the stator (114) by the action of changes in the fluid flow through the conduit system (130) caused by the operation of the valve (111, 131).

Data are transmitted through a column of drilling fluid in a drill string that is being applied in drilling a borehole in an underground formation. The data are in the form of pressure waves (such as pressure pulses) and are generated by means of a downhole liquid motor (34, 35) that is driven by the drilling fluid. The pressure waves are generated by varying the load on the electric generator (38) driven by the liquid motor. The load is varied to a predetermined pattern that is representative of the data to be transmitted.

A mud by-pass regulator apparatus for regulating the flow of drilling fluid through the turbine of a downhole power generator supply in a measurement while drilling system includes a valve (94), valve actuator (50), and a valve actuator control (60, 64, 72). Pressure differential across the turbine is sensed by a piston (60) located between high pressure (72) and low pressure (64) chambers increase in pressure differential moves valve actuator (50) against the bias of a spring (58) to move valve (94) away from turbine (88) and allow more fluid to by-pass the turbine. This ensures regulation of the drilling fluid flowing through the power supply so that its operation is maintained within required limits of the downhole portion of the measurement while drilling apparatus.

The present invention relates to a downhole drilling system (100), comprising: a drill string (1) having a drill head (6) configured to drill a borehole (2) having a borehole wall (3) forming an annulus (4) between the drill string and the borehole, a plurality of sensor units (10) forming a mesh network, wherein each one of said sensor units is distributed in a drilling fluid flowing in the annulus and in the drill string, and at least one of said sensor units is provided with a detector (14) for measuring position data. The present invention also relates to a method for providing a downhole drilling system according to the present invention and to a method for determining drilling direction.