Downhole hydraulic control system
AssigneeSmith International, Inc.
InventorJay Milton Eppink
Life of this patent
Estimating the term…
Abstract
A purely mechanical hydraulic control system includes at least one drilling fluid chamber and a hydraulic fluid chamber. A system pressure spring is deployed in one of the drilling fluid chamber(s) between a positioning piston and a system pressure piston. The spring is disposed to pressurize oil in the hydraulic fluid chamber via applying a spring force to the system pressure piston. When the system is actuated (e.g., via turning on the mud pumps), the positioning piston is urged in place against a stop (e.g., a shoulder) thereby compressing the system pressure spring and pressurizing oil in the hydraulic chamber. The invention advantageously converts highly variable drilling fluid pressure to a near constant pressure hydraulic fluid.
Claims25
A downhole tool comprising:
- a substantially cylindrical drill collar having a through bore;
- a first drilling fluid chamber connected with the through bore via an inlet port, the first drilling fluid chamber located between a positioning piston and the inlet port, the positioning piston disposed to reciprocate between first and second opposed positions, the positioning piston being disposed in the first position when a pressure in the drilling fluid in the through bore is greater than a predetermined threshold;
- a hydraulic fluid chamber;
- and
- a system pressure spring deployed between the positioning piston and a system pressure piston, the system pressure piston in contact with the hydraulic fluid chamber, the system pressure spring disposed to pressurize hydraulic fluid in the hydraulic fluid chamber when the positioning piston is in the first position.
A downhole tool comprising:
- a substantially cylindrical though bore;
- a hydraulic module in fluid communication with a hydraulic replenishing system, the hydraulic replenishing system disposed to replenish hydraulic fluid in the hydraulic module;
- and
- a hydraulic fluid channel disposed between a hydraulic chamber in the replenishing system and a hydraulic chamber in the hydraulic module;
- the fluid channel including a check valve and a push rod deployed therein, the check valve disposed to permit fluid flow from the hydraulic module to the replenishing system, the push rod deployed between a piston in the hydraulic module and the check valve, the piston in the hydraulic module disposed to urge the push rod into contact with the check valve thereby opening the check valve when a fluid volume in the hydraulic module is below a predetermined threshold, said opening of the check valve allowing hydraulic fluid to flow down a pressure gradient from the replenishing system to the hydraulic module.
A hydraulic module for use in a downhole tool, the hydraulic module disposed to provide substantially constant hydraulic pressure, the hydraulic module comprising:
- first and second drilling fluid chambers, the first drilling fluid chamber in fluid communication with drilling fluid inside the tool, the second drilling fluid chamber in fluid communication with drilling fluid outside the tool;
- a hydraulic fluid chamber;
- a positioning piston deployed between the first and second drilling fluid chambers, the positioning piston disposed to displace between first and second longitudinally opposed positions, the first position adjacent a stop in the second drilling fluid chamber and the second position adjacent an inlet port disposed to permit drilling fluid in the through bore to enter the first drilling fluid chamber;
- a system pressure piston deployed between the second drilling fluid chamber and the hydraulic fluid chamber;
- and
- a system pressure spring deployed in the second drilling fluid chamber, the system pressure spring being loaded between the positioning piston and the system pressure piston, the system pressure spring disposed to pressurize hydraulic fluid in the hydraulic fluid chamber when the positioning piston is in the first position.
Dependencies are inferred from the claim text.