Electric well service rig

A mobile service rig for servicing a pumpjack installation, the pumpjack installation comprising a pumpjack and a circular area of land, the pumpjack being selectively activated and deactivated, the circular area of land being defined by a 200-foot radius from a centerpoint of a wellbore, the pumpjack being within the circular area of land, the pumpjack receiving electrical power from an electrical power grid when the pumpjack is activated to draw a fluid up through the wellbore, the pumpjack being inactive when the pumpjack is deactivated, the mobile service rig being operable selectively in a travel mode for traveling, a wellstring pulling mode for pulling a wellstring up from within the wellbore, a wellstring insertion mode for lowering the wellstring down into the wellbore, and a setup mode;

• the mobile service rig comprising:
• a chassis;
• a hoist drum supported by the chassis;
• a first electric motor;
• a gearbox coupling the first electric motor to the hoist drum, the first electric motor being coupled to rotate the hoist drum at least sometimes during the wellstring pulling mode;
• a rechargeable electric power storage system supported by the chassis, the rechargeable electric power storage system being connected to deliver electrical power to the first electric motor during the wellstring pulling mode;
• an electrical cable connecting the rechargeable electric power storage system to the pump jack installation during at least one of the wellstring pulling mode and the wellstring insertion mode, the electrical cable being disconnected from at least one of the pumpjack installation and the rechargeable electric power storage system during the travel mode;
• an auxiliary electric motor supported by the chassis, the auxiliary electric motor being smaller than the first electric motor, the auxiliary electric motor being powered by the rechargeable electric power storage system;
• a hydraulic pump powered by the auxiliary electric motor;
• a tongs tool with a hydraulic motor powered by the hydraulic pump, the tongs tool being adapted to apply torque to the wellstring;
• a mast being pivotal relative to the chassis between a raised position and a lowered position;
• a hydraulic cylinder connected to move the mast between the lowered position and the raised position;
• and
• a winch supported by the chassis, each of the tongs tool, the hydraulic cylinder and the winch being powered by the hydraulic pump, which in turn is powered by the auxiliary electric motor, which is energized by the rechargeable electric power storage system.

A mobile service rig method for lifting and lowering a wellstring, the mobile service rig method involves the use of a mobile service rig that comprises at least one of a chassis, a rechargeable electric power storage system, a first electric motor, a hoist drum, a clutch coupling the first electric motor to the hoist drum, and a brake associated with the hoist drum, wherein the wellstring comprises a plurality of elongate members, the plurality of elongate members being of a quantity that varies upon progressively assembling and disassembling the wellstring, lifting of the wellstring occurs during at least part of a wellstring removal period, lowering of the wellstring occurs during at least part of a wellstring insertion period, the mobile service rig method comprising:

• supporting the set of blocks with the hoist drum;
• connecting the set of blocks to the wellstring during the wellstring removal period;
• conveying electrical energy from the rechargeable electric power storage system to the first electric motor to rotate the first electric motor and the hoist drum in a forward direction, thereby lifting the wellstring with the set of blocks to a raised elevation during the wellstring removal period;
• disengaging the clutch and engaging the brake to momentarily hold the wellstring at the raised elevation during the wellstring removal period;
• partially disassembling the wellstring below the set of blocks during the wellstring removal period;
• disconnecting the set of blocks from the wellstring during the wellstring removal period;
• releasing the brake after disconnecting the set of blocks from the wellstring during the wellstring removal period;
• allowing the set of blocks to descend by gravity so the hoist drum rotates in a reverse direction during the wellstring removal period;
• applying the brake to momentarily stop the hoist drum from continuing to rotate and thereby momentarily stop the set of blocks from continuing to descend during the wellstring removal period;
• connecting the set of blocks to the wellstring during the wellstring insertion period;
• engaging the clutch during the wellstring insertion period;
• releasing the brake during the wellstring insertion period, thereby causing the wellstring to descend by gravity during the wellstring insertion period;
• rotating the hoist drum in the reverse direction as a consequence of the wellstring descending by gravity during the wellstring insertion period;
• and
• applying the brake to momentarily stop the wellstring at a lowered elevation during the wellstring insertion period.

A mobile service rig method for operating a mobile service rig, the mobile service rig method involving the use of at least one of an electrical power grid, a wire, a pumpjack installation, a pumpjack motor, a wellstring, and a wellbore;

• the mobile service rig comprising a rechargeable electric power storage system, an electric motor, and a hoist drum;
• the mobile service rig method having selectively a pumping period during which the pumpjack motor is activated and a service period during which the pumpjack motor is deactivated, the service period having selectively a wellstring pulling mode in which the mobile service rig lifts the wellstring up from within the wellbore at the pumpjack installation and a wellstring insertion mode in which the mobile service rig lowers the wellstring down into the wellbore;
• the mobile service rig method comprising:
• conveying selectively a pumpjack motor current and a charging current through the wire that couples the electrical power grid to the pumpjack motor;
• conveying the pumpjack motor current from the electrical power grid, through the wire and to the pumpjack motor of the pumpjack installation and doing so during the pumping period;
• discontinuing the conveying of the pumpjack motor current to the pumpjack motor during the service period;
• conveying the charging current from the electrical power grid, through the wire and to the rechargeable electric power storage system on the mobile service rig during the service period;
• conveying a supply current from the rechargeable electric power storage system to the electric motor during the wellstring pulling mode of the service period, the electric motor being bigger than the pumpjack motor, the supply current to the electric motor during the wellstring pulling mode of the service period being greater than the pumpjack motor current during the pumping period;
• and
• rotating the hoist drum via the electric motor during the wellstring pulling mode of the service period.