Hydraulic Oil Selection
Hydraulic Oil Selection
(OP)
I'm evaluating a non-return hydraulic system that will run vertically 15,000 ft down a natural gas well. This system has a switching valve on the surface and it vents one line while pressurizing the other line to move a downhole hydraulic piston that is driving a piston pump.
At this depth in 1-inch tubing the two big issues are oil specific gravity and compressibility. SG relates directly to the amount of pressure that I have to design the hydraulic cylinder barrel for. Lighter oil means smaller wall thickness and I can either fit inside a smaller wellbore or can pump more water from the well. This is pretty important, but if I change from the oil I'm using today (SG=0.85) to the lightest oil I've found (SG=0.802) then I can only carve out 1/16 inch of wall thickness, good, but not wonderful.
The bigger issue is compressibility. The oil I'm using now has a compressibility of 0.4%/1000 psi. This means that if I apply 3,000 psig to 400 gallons of fluid I need to make up (including the pump travel) 8 gallons. At 3 gpm it takes nearly 3 minutes to stroke the pump each way, virtually all of it spent compressing the oil.
Does anyone know of an oil (I'm using ESSO Nuto-A10) that might be lighter and less compressible?
David
At this depth in 1-inch tubing the two big issues are oil specific gravity and compressibility. SG relates directly to the amount of pressure that I have to design the hydraulic cylinder barrel for. Lighter oil means smaller wall thickness and I can either fit inside a smaller wellbore or can pump more water from the well. This is pretty important, but if I change from the oil I'm using today (SG=0.85) to the lightest oil I've found (SG=0.802) then I can only carve out 1/16 inch of wall thickness, good, but not wonderful.
The bigger issue is compressibility. The oil I'm using now has a compressibility of 0.4%/1000 psi. This means that if I apply 3,000 psig to 400 gallons of fluid I need to make up (including the pump travel) 8 gallons. At 3 gpm it takes nearly 3 minutes to stroke the pump each way, virtually all of it spent compressing the oil.
Does anyone know of an oil (I'm using ESSO Nuto-A10) that might be lighter and less compressible?
David





RE: Hydraulic Oil Selection
Try posting on www.noria.com. You might get some input there.
Tom
RE: Hydraulic Oil Selection
Ted
RE: Hydraulic Oil Selection
David
RE: Hydraulic Oil Selection
That way the oil would alrady be compressed at the pump and the cycle would not have the 3 minute pause you are experiencing.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: Hydraulic Oil Selection
David
RE: Hydraulic Oil Selection
Was the operation improved??
By how much??
What Failed in that short time period??
Was the improvement great enough for you to try other valve designs??
It seems that if a Piston Pump can operate in that atmosphere a switching valve could be made that would also. Design one that works and patent it and charge big bucks for replacing the unsatisfactory arrangement presently in use.
Just a thought.
Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING
RE: Hydraulic Oil Selection
Offshore Engineering&Design
RE: Hydraulic Oil Selection
I might as well use water (which has a bulk modulus over twice as high as mineral oil so about half the compressibility and no degradation with increased temp).
David