Oil well pump
A pump system for use in with a downhole pipe string has a pump comprising at least one cylinder with at least one piston inside the cylinder, the movement of the piston causing fluid to be drawn into the pump through a pump inlet before being pushed out through a pump outlet. The pump is housed in a tube having a cammed surface formed by internal wall of the tube, and the piston has a cam follower such that rotation of the piston relative to the tube causes the piston to move relative to the cylinder. Further, a pump system is shown which has two or more such pumps arranged along the downhole pipe string, the pump outlets feeding into a common manifold. The strokes of the piston or pistons of one pump may be out of step with the strokes of the piston or pistons of another pump such that the outlet stream is more uniform.
1. A modular pump system for use downhole in a well, having at least a first pump comprising a tube and a cylinder block, the cylinder block defining at least one cylinder with a respective piston inside the cylinder, the movement of the piston in the cylinder causing fluid to be drawn into the first pump through a pump inlet before being pushed out through a pump outlet, the cylinder block being housed in the tube, the tube having a cammed surface formed by an internal wall of the tube, the piston having a cam follower such that rotation of the cylinder block to the tube causes the piston to move relative to the cylinder;
the first pump having two ends, the tube and the cylinder block being connectable at each of the ends in series relation respectively to the corresponding tube and cylinder block of a further said pump such that the tube is rotationally locked to the corresponding tube of the further said pump to form a modular pump assembly.
2. A modular pump system according to claim 1 , wherein the pump outlet feeds into a bore which extends through the pump, the bore being connectable at each of the ends to the corresponding bore of a further said pump to form a common manifold.
3. A modular pump system according to claim 2 , wherein the tube and the cylinder block are connectable at each of the ends respectively to the corresponding tube and cylinder block of a further said pump in a rotationally oriented position, so that the strokes of the piston or pistons of the first pump are out of step with the strokes of the piston or pistons of the further pump such that the outlet stream is more uniform.
4. A modular pump system according to claim 1 , wherein the cammed surface is a groove formed in the internal wall of the tube.
5. A modular pump system according to claim 4 , wherein the piston is axially aligned with the tube.
6. A modular pump system according to claim 5 , wherein at least a further piston is axially aligned with the tube, the further piston acting as a valve to control a path from the cylinder to the pump inlet or pump outlet.
7. A modular pump system according to claim 1 , wherein the cammed surface is an elliptical surface lying in a plane oblique to the tube's axis.
8. A modular pump system according to claim 1 , wherein pumping surfaces of the first pump are hard faced and honed to a precision fit.
9. A modular pump system according to claim 2 , wherein the bore extends axially centrally through the pump.
10. A modular pump system according to claim 1 , wherein the tube includes a respective splined connection means at each of the ends whereby the tube may be connected in series to the corresponding tube of a further said pump.
11. A modular pump system according to claim 10 , wherein the cylinder block includes a respective threaded connection means at each of the ends whereby the cylinder block may be connected in series to the corresponding cylinder block of a further said pump.