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# Calculate fluid specific gravity

## Calculate fluid specific gravity

(OP)
dear all

i was a question regarding fluid specific gravity

i was infrmed that Watercut is 30 % so oil is 70% and water is 30%,so i calculated specific garavity by :-

W.S.G= 0.3 * 1.016,AND o.s.g = 0.7 * 0.842 Then added them to get total fluid S.G ,,am i rigth ?.

also how i can calculate this fluid viscosity,centipoise.?

### RE: Calculate fluid specific gravity

Your arithmetic is correct, if your species specific gravity is correct then you should hove the correct specific gravity.

Finding the viscosity of a mix of liquids is much more difficult. If you use the mole percent contribution of each of the species you will be ignoring interfacial reactions which can be larger than the friction component of parasitic pressure drop. The only reliable method I've found has been experimentation. Even experimentation is of limited value since small changes in fluid temperature make a big change in viscosity.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

### RE: Calculate fluid specific gravity

If it was a hydrocarbon liquid other than oil + water, I might try ASTM D7152 to try and approximate the viscosity. Otherwise, one is probably compelled to purchase one of the scholarly articles related to the prediction of oil-water emulsions; the ones I found were about \$40.00 USD.

Who is right doesn't matter. What is right is all that matters.

### RE: Calculate fluid specific gravity

(OP)
dear all

thanks for your answers,,i need the viscsty in drwing pump curves,,as i set it at one but i dont know real number

### RE: Calculate fluid specific gravity

No number is ever going to be reliable. Crude is a tough fluid. Very small changes in either temperature and pressure can put you into a region where emulsions are common. No pump curve is going to tell you how to pump an emulsion with a dynamic pump (generally you want to use a low shear PD pump like a PCP). You can make up a number (which is about all you are going to get from a correlation or an experiment, a made up number) but you have to realize that the fluid interactions can result in any value for viscosity at any moment.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

### RE: Calculate fluid specific gravity

agree with David, temperature is very important and the experimental way is probably the only reliable if you want to know a number for certain. Most process simulation tool will give you an estimate - but not for emulsions. But its not a given thing that water and a crude oil will form an emulsion.

Best regards, Morten

### RE: Calculate fluid specific gravity

(OP)

i have another question.in some wells ,wehn i start esp well operating with a sensor,the application engineer tells me the pump will start to produce oil at certian Pd,,,how can he figure certian Pi and Pd ,how he can know the limits of each

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