Fluid pumping apparatus and method of pumping fluid

A fluid pumping apparatus comprising

• an elongate body having a longitudinal axis, a hollow interior, a lower end and an upper end, and a continuous side wall, said body being closed at its lower end and open at its upper end;
• a plunger assembly having a piston with a longitudinal axis, a lower face and an upper face, disposed in the interior of said body in coaxial substantially fluid-tight sliding relation therewith, said piston dividing said body into a lower chamber and an upper chamber, an elongate plunger shaft having a longitudinal axis, a lower end and an upper end, interconnected at its lower end to said upper face of said piston in coaxial alignment therewith, extending from said piston through said open upper end of said body in substantially fluid-tight sliding relation with said body at said upper end, and an elongate fluid aperture extending from said lower face of said piston, through said piston and through said plunger shaft to form a fluid passageway from said lower chamber of said body to the exterior of said body above said upper end thereof;
• inlet valve means communicating between said lower chamber of the interior of said body and the exterior of said body for the purpose of allowing fluid to flow into said lower chamber from the exterior of said body through said inlet valve means and preventing fluid from flowing from said lower chamber to the exterior of said body through said inlet valve means;
• lower fluid control means at said lower end of said fluid aperture for the purpose of allowing fluid to flow from said lower chamber of said body into said fluid aperture and preventing fluid from flowing from said fluid aperture into said lower chamber;
• and
• upper fluid control means at said upper end of said fluid aperture for the purpose of allowing fluid to flow from said fluid aperture to the exterior of said body and preventing fluid from flowing from the exterior of said body into said fluid aperture.

A method of pumping fluid from a well extending from the surface into the ground, through a string of hollow production tubing extending through the well bore, using a reciprocating pumping apparatus disposed in the well bore, connected to the production tubing and activated by a pump driver, such pumping apparatus having an elongate hollow body stationary in relation to the well bore and connected at its upper end to the lower end of the production tubing, a piston of slightly smaller cross-sectional dimension than the inner dimension of said body and having a lower face, disposed in the body in tightly fitting sliding relation and dividing the body into a lower chamber and an upper chamber, a piston shaft of substantially smaller cross-sectional dimension than the piston, connected at its lower end to the piston in coaxial relation, extending upward from the piston through the upper end of the body in fluid-tight sliding relation therewith and into the production tubing and connected at its upper end to the pump driver, a fluid conduit extending longitudinally through the piston and piston shaft, a one-directional fluid inlet valve at the lower end of the body to allow fluid to flow into the lower chamber of the body, a one-directional lower control valve at the lower end of the fluid conduit to allow fluid to flow into the conduit, and a one-directional upper control valve at the upper end of the fluid conduit to allow fluid to flow from the conduit into the production tubing, comprising the steps of

• lifting the piston and the piston shaft in the body of the pumping apparatus through the full upstroke of the pumping apparatus, with the lower fluid control valve and the upper fluid control valve closed and with the fluid inlet valve open, drawing fluid into the lower chamber of the body;
• closing the fluid inlet valve and initiating lowering of the piston and piston shaft in the body of the pumping apparatus, opening the lower fluid control valve and the upper fluid control valve to open a fluid passageway from the lower chamber of the body through the fluid conduit and into the production tubing;
• continuing lowering of the piston and piston shaft in the body of the pumping apparatus through the full downstroke of the pumping apparatus, forcing fluid from the lower chamber through the fluid conduit and into the production tubing;
• closing the lower fluid control valve and the upper fluid control valve and initiating raising of the piston and piston shaft in the body of the pumping apparatus, opening the fluid inlet valve and beginning to draw fluid into the lower chamber of the body of the apparatus;
• and
• repeating the above steps to continue forcing fluid into the production tubing on each downstroke of the pumping apparatus and produce fluid from the production tubing.