Abstract: A differential pressure operated free piston for lifting well fluids from a subterranean reservoir to the surface through a well conduit. The free piston includes a piston body adapted for up and down sliding disposition within the conduit and a sealing assembly carried in a cylindrical space surrounding the piston body. The sealing assembly includes upper and lower juxtaposed sets of longitudinally separated cylindrical segments providing relatively smooth cylindrical surfaces on the exterior thereof for sliding and sealing contact with inner walls of the conduit, the upper and lower set of segments being radially oriented so that separations between the segments of the upper set and separations between the segments of the lower set are not aligned, providing a seal which, when pressure in the well conduit near the surface is subsequently reduced, sufficiently elevates the piston and well fluids thereabove to the surface.

Abstract: A gas operated plunger for lifting well fluids from a subterranean reservoir to the surface through a well conduit comprising: a plunger body slidably mountable within the conduit having an upper portion, a lower portion and an intermediate cylindrical portion of reduced diameter; and a sealing assembly surrounding the intermediate cylindrical portion of the plunger body. The sealing assembly may include a plurality of longitudinally divided cylindrical segments of relatively smooth cylindrical surfaces for sliding and sealing contact with the well conduit walls to provide a seal which allows the plunger to gravitate through the well conduit to the reservoir and provides sufficient sealing upon an increase in gas pressure therebelow to elevate the plunger and well fluids thereabove to the surface.

Abstract: A gas operated, plunger lift type pump for use in a subterranean well conduit which extends from a pool of well liquids to the surface comprises a tubular plunger slidably and sealingly mounted in the well conduit and defining a fluid flow passage through the tubular body. An annular valve seat is fixedly mounted within the tubular body and an axially shiftable valve head is engagable with the valve seat to prevent fluid flow through the fluid passage. The valve head is biased to an open position by a surface applied trapped fluid pressure which approximates the hydrostatic pressure existing in the well at the liquid level to which the plunger is permitted to descend, and is further retained in the open position by a latching collet. As the plunger rises in the well due to the gas pressure existing below the plunger, it will raise the fluids trapped above the plunger to discharge through vertically spaced discharge ports.

Abstract: In accordance with an illustrative embodiment of the present invention, a side pocket mandrel having a side pocket laterally offset from the open bore has an opening at the upper end of the pocket adapted to receive a gas lift valve. The axis of the opening is inclined in a downward and inward direction toward the axis of the open bore. A kickover tool for replacing and removing valves includes an orienting section having angularly spaced dogs that are cooperable with a sleeve in the mandrel to cause orientation of the tool and to trigger longitudinal movement of a control rod. Rod movement actuates guides on a pivot arm that cooperates with rails or the like in the mandrel to cause the valve to be inserted through the opening to a position extending upwardly into the annulus with a packing sub thereon engaging the opening.

Abstract: Disclosed is releasable plugging apparatus for selectively closing a tubular member to permit fluid pressure buildup therein. When the fluid pressure is then decreased, a sealing device of the apparatus may be released, and the tubular member subsequently opened. Holding apparatus secures the sealing device in place until a compressed spring is permitted to move a piston so as to permit the holding apparatus to release the sealing device. A locking device prevents such movement by the piston until the pressure buildup first moves the piston in the opposite direction to release the locking device and to further compress the spring. The tubular member is thus not unplugged until the fluid pressure is decreased, thereby avoiding a large pressure pulse which might result if the sealing device were released with the fluid pressure at a high value. The embodiments described are particularly applicable for use with hydraulically-operated well tools, such as well packers.

Abstract: Disclosed is a pumping system using a pneumatically powered, submerged pump for lifting high viscosity oil from a well. The pump includes a flexible, bag-shaped expansible member or "bladder" mounted within a surrounding housing. Pressurized gas is supplied from the well surface to the bladder through a supply line. An inlet check valve permits oil in the formation to flow into the housing when the bladder is collapsed. When the bladder is expanded or displaced by the gas, the oil in the housing is displaced through an outlet check valve into a flow line which extends to the well surface. A submerged control valve channels gas into the bladder to control the bladder expansion. The control valve also functions to permit the gas in the bladder to flow into a vent tube to control bladder deflation.In a modified form of the invention, oil flowing into the housing expands the bladder and gas supplied to the housing collapses the bladder.

Abstract: Artificial lift apparatus for use in a well having an outer pipe string for flow of a first fluid and an inner pipe string for flow of a second fluid. The apparatus may comprise a tubular receiver for connection in the inner pipe string and having ports for providing communication between the inner and outer pipe string. The receiver may include an inner tubular member and a concentrically surrounding outer tubular member defining an annular passageway therebetween through which at least a portion of the first fluid flow may pass. The apparatus may also include a well tool adapted for movement through the inner pipe string for engagement with the receiver inner tubular member and being provided with at least one valve for controlling fluid flow between the inner and outer pipe strings through the ports.