## Water Injection Well - Pressure Drop

## Water Injection Well - Pressure Drop

(OP)

Hello to All,

I would like to discuss some doubts that I have about the way to calculate the pressure drop in a water injection well during fracture operation.

Here is my escenario, I have a 2D well path (vertical 9000 ft; horizontal 8000 ft), the fluid injected is slickwater (density 1300 km/m3) with propant. The pump pressure in the wellhead is 65000 kpa.

My first approach was to use Bernoulli with the addicional term of Head Loss for the horizontal path. This is a turbulent fluid so I calculated the friction factor in the head loss term using colebrook eq. When I try to do the same calcuations using WellFlo I can´t achieve the same results for high flow rate (up to 3 m3/min). In WellFlo I set the Begg & Brill (modified) correlation.

Does anyone know why the difference?. Is it ok to use bernoulli for solving this type of problem (I think it is..). I would appreciate any help on this issue!.

Thanks in advance!

I would like to discuss some doubts that I have about the way to calculate the pressure drop in a water injection well during fracture operation.

Here is my escenario, I have a 2D well path (vertical 9000 ft; horizontal 8000 ft), the fluid injected is slickwater (density 1300 km/m3) with propant. The pump pressure in the wellhead is 65000 kpa.

My first approach was to use Bernoulli with the addicional term of Head Loss for the horizontal path. This is a turbulent fluid so I calculated the friction factor in the head loss term using colebrook eq. When I try to do the same calcuations using WellFlo I can´t achieve the same results for high flow rate (up to 3 m3/min). In WellFlo I set the Begg & Brill (modified) correlation.

Does anyone know why the difference?. Is it ok to use bernoulli for solving this type of problem (I think it is..). I would appreciate any help on this issue!.

Thanks in advance!

## RE: Water Injection Well - Pressure Drop

Every so often, in very small dP cases, that STUPID modification of Bernoulli to tack on a meaningless headloss term matches actual data within a couple of dozen percentage points and everyone sings Hosannas to its vast usefulness. Nonsense.

No, Bernoulli is not appropriate. You can try to use D'Arcy-Weisbach, but it assumes an absolutely incompressible fluid and your hydrostatic plus dynamic pressure is high enough (around 130 MPa minus friction) that you are probably compressing the liquid 20% or so. If you use that, be really careful how you calculate your friction factor, you are going to be way outside the horizontal straight line portion of the Moody Diagram.

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: Water Injection Well - Pressure Drop

What abaut the pressure drop correlations like beggs and brill amongst others?.

## RE: Water Injection Well - Pressure Drop

For an injection stream of single-phase water (even if it does have a specific gravity of 1.3, it should still be mostly Newtonian) I'd tend to calculate a friction drop using D'Arcy-Weisbach (ignoring elevation change) and then determine injection pressure as Surface Pressure + Hydrostatic Pressure - Friction Drop. Compressibility of the water is going to add significantly to your uncertainty, but it probably is not big enough to lead you to a different decision.

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: Water Injection Well - Pressure Drop

Is it possible to apply the Fanning-Liquid Correlation for single phase liquid with good results?. Do you have experience using this one?.

I´m having problem in estimating the friction factor with D'Arcy.

Furthermore, I´m a little confuse about the effect of the hydrostatic colum on the comprensibility of the water, the height of the vertical section is about 3 km and the horizontal section is about 4 km of lenght. How can I check this?

Could your recommend some bibliography, paper, info about this issues?.

Thanks again!

## RE: Water Injection Well - Pressure Drop

## RE: Water Injection Well - Pressure Drop

You can look at any of the closed form equations, but all of them have a rigid set of assumptions that allow them to estimate friction factor in a single step.

I'm not familiar with Fanning Liquid Correlation, but I did find a site that indicated that vertical flow violated one (or more) of Fanning's underlying assumptions.

No I don't have a bibliography.

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: Water Injection Well - Pressure Drop

## RE: Water Injection Well - Pressure Drop

MuleShoe Engineering