Patent ID: 7273109
Filing Date: 2007-09-25
Classification: E21B

Abstract:
1. A tool for moving within a passage, comprising: an elongated body; a first fluid-actuated gripper assembly engaged with and longitudinally movable with respect to the body, the first gripper assembly configured to grip onto an inner surface of the passage when the first gripper assembly receives a pressurized fluid; a first barrel surrounding and engaged with the body, the first barrel being longitudinally fixed with respect to at least one end of the first gripper assembly and longitudinally movable with respect to the body, the first barrel and the body defining a first annular space therebetween, wherein one or more interfaces between the first barrel and the body are sealed to substantially prevent escape of fluid from the first annular space to an exterior of the first barrel; a first piston longitudinally fixed with respect to the body and positioned within the first barrel, the first piston fluidly separating the first annular space into aft and forward chambers of the first barrel, wherein sizes of the aft and forward chambers of the first barrel vary as the first piston moves longitudinally within the first barrel; a second fluid-actuated gripper assembly engaged with and longitudinally movable with respect to the body, the second gripper assembly configured to grip onto the inner surface of the passage when the second gripper assembly receives a pressurized fluid; a second barrel surrounding and engaged with the body, the second barrel being longitudinally fixed with respect to at least one end of the second gripper assembly and longitudinally movable with respect to the body, the second barrel and the body defining a second annular space therebetween, wherein one or more interfaces between the second barrel and the body are sealed to substantially prevent escape of fluid from the second annular space to an exterior of the second barrel; a second piston longitudinally fixed with respect to the body and positioned within the second barrel, the second piston fluidly separating the second annular space into aft and forward chambers of the second barrel, wherein sizes of the aft and forward chambers of the second barrel vary as the second piston moves longitudinally within the second barrel; a valve assembly within the tool for directing fluid to and from the first and second gripper assemblies, the aft and forward chambers of the first barrel, and the aft and forward chambers of the second barrel to propel the tool within the passage; a closed system fluid circuit within the tool, for circulating a fluid through the valve assembly, the gripper assemblies, and the barrels to propel the tool within the passage; a pump configured to circulate fluid within the closed system fluid circuit; and a motor configured to power the pump; wherein the valve assembly comprises a main valve having a first position in which the main valve provides (1) a flow path from an outlet of the pump to the first gripper assembly and to the aft chamber of the first barrel, (2) a flow path from the pump outlet to the forward chamber of the second barrel, (3) a flow path from the second gripper assembly and the aft chamber of the second barrel to a low-pressure chamber that conveys fluid to an inlet of the pump, and (4) a flow path from the forward chamber of the first barrel to the low-pressure chamber, the main valve having a second position in which the main valve provides (1) a flow path from the pump outlet to the second gripper assembly and to the aft chamber of the second barrel, (2) a flow path from the pump outlet to the forward chamber of the first barrel, (3) a flow path from the first gripper assembly and the aft chamber of the first barrel to the low-pressure chamber, and (4) a flow path from the forward chamber of the second barrel to the low-pressure chamber.