Abstract: A hydraulically powered tractor includes an elongated body, two gripper assemblies, at least one pair of aft and forward propulsion cylinders and pistons, and a valve system. The valve system comprises an inlet control valve, a two-position propulsion control valve, a two-position gripper control valve, two cycle valves, and two pressure reduction valves. The inlet control valve spool includes a hydraulically controlled deactivation cam that locks the valve in a closed position, rendering the tractor non-operational. The propulsion control valve is piloted on both ends by fluid pressure in the gripper assemblies. The propulsion control valve controls the distribution of operating fluid to and from the propulsion cylinders, such that one cylinder performs a power stroke while the other cylinder performs a reset stroke. Each end of the gripper control valve is piloted by a source of high-pressure fluid selectively admitted by one of the cycle valves.

Abstract: A gripper assembly for anchoring a tractor within a downhole passage and for assisting movement of the tractor within the passage. The gripper assembly includes an elongated mandrel and flexible toes that can be radially displaced to grip onto the surface of the passage. The toes are displaced by the interaction of a driver slidable on the mandrel and a driver interaction element on the toes. In one embodiment, the toes are displaced by the interaction of rollers and ramps that are longitudinally movable with respect to one another. In another embodiment, the toes are displaced by the interaction of toggles that rotate with respect to the toes.

Abstract: A tractor for moving within a borehole comprises an elongated tractor body and two propulsion assemblies that are longitudinally movably engaged with the body. The tractor body has annular pistons configured to receive hydraulic thrust to propel the body longitudinally. Each propulsion assembly includes a gripper and one or more propulsion cylinders. The gripper has an actuated position in which the gripper limits relative movement between the gripper and the inner surface of the borehole, and a retracted position in which the gripper permits substantially free relative movement between the gripper and the inner surface of the borehole. Each propulsion cylinder contains one of the pistons. The tractor includes a control assembly having a plurality of valves and hydraulic circuitry which control the sequencing of fluid distribution to the propulsion cylinders, and of the actuation and retraction of the grippers. A throttle valve controls the fluid flowrate to the pistons.

Abstract: A sensor assembly including a sensor mounted on the piston and a transmitter mounted on either the piston or cylinder. Preferably the transmitter includes a wheel which engages the wall of the cylinder so as to rotate as the piston reciprocates within the cylinder. The wheel includes one or more magnets which emit a magnetic field that is received by the sensor as the wheel rotates whereby the sensor provides a signal indicative of the rotation of the wheel. The sensor then sends the signal to a logic component which determines the direction, travel and position of the piston within the cylinder.

Abstract: A downhole drilling tractor for moving within a borehole comprises a tractor body, two packerfeet, two aft propulsion cylinders, and two forward propulsion cylinders. The body comprises aft and forward shafts and a central control assembly. The packerfeet and propulsion cylinders are slidably engaged with the tractor body. Drilling fluid can be delivered to the packerfeet to cause the packerfeet to grip onto the borehole wall. Drilling fluid can be delivered to the propulsion cylinders to selectively provide downhole or uphole hydraulic thrust to the tractor body. The tractor receives drilling fluid from a drill string extending to the surface. A system of spool valves in the control assembly controls the distribution of drilling fluid to the packerfeet and cylinders. The valve positions are controlled by motors. A programmable electronic logic component on the tractor receives control signals from the surface and feedback signals from various sensors on the tool.

Abstract: A downhole drilling tractor for moving within a borehole comprises a tractor body, two packerfeet, two aft propulsion cylinders, and two forward propulsion cylinders. The body comprises aft and forward shafts and a central control assembly. The packerfeet and propulsion cylinders are slidably engaged with the tractor body. Drilling fluid can be delivered to the packerfeet to cause the packerfeet to grip onto the borehole wall. Drilling fluid can be delivered to the propulsion cylinders to selectively provide downhole or uphole hydraulic thrust to the tractor body. The tractor receives drilling fluid from a drill string extending to the surface. A system of spool valves in the control assembly controls the distribution of drilling fluid to the packerfeet and cylinders. The valve positions are controlled by motors. A programmable electronic logic component on the tractor receives control signals from the surface and feedback signals from various sensors on the tool.

Abstract: A tractor for moving within a borehole comprises an elongated tractor body and two propulsion assemblies that are longitudinally movably engaged with the body. The tractor body has annular pistons configured to receive hydraulic thrust to propel the body longitudinally. Each propulsion assembly includes a gripper and one or more propulsion cylinders. The gripper has an actuated position in which the gripper limits relative movement between the gripper and the inner surface of the borehole, and a retracted position in which the gripper permits substantially free relative movement between the gripper and the inner surface of the borehole. Each propulsion cylinder contains one of the pistons. The tractor includes a control assembly having a plurality of valves and hydraulic circuitry which control the sequencing of fluid distribution to the propulsion cylinders, and of the actuation and retraction of the grippers. A throttle valve controls the fluid flowrate to the pistons.

Abstract: A tractor for moving within a borehole comprises an elongated tractor body and two propulsion assemblies that are longitudinally movably engaged with the body. The tractor body has annular pistons configured to receive hydraulic thrust to propel the body longitudinally. Each propulsion assembly includes a gripper and one or more propulsion cylinders. The gripper has an actuated position in which the gripper limits relative movement between the gripper and the inner surface of the borehole, and a retracted position in which the gripper permits substantially free relative movement between the gripper and the inner surface of the borehole. Each propulsion cylinder contains one of the pistons. The tractor includes a control assembly having a plurality of valves and hydraulic circuitry which control the sequencing of fluid distribution to the propulsion cylinders, and of the actuation and retraction of the grippers. A throttle valve controls the fluid flowrate to the pistons.