Annulus gas rate 2

[muli]

thread469-189800
Assuming that besides reducing back pressure on the formation you also want to use the annulus gas to fuel a gas engine as your pumping unit prime mover, does anybody know a "low tech" wellsite test to determine the gas daily flow rate? I mean, something without orifice plates or flowmeters, and similar to the "Bucket Test" we use to estimate oil production.

 

[zdas04]

Without any instrumentation you can guess.

I suppose you can put a recording gauge upstream of a valve, start it recording and open the valve to atmosphere. Until the pressure is around 15 psig the flow will be choked and you can figure volume flow rate from the sonic velocity at each pressure and the area of the exit pipe.

David

 

[dcasto]

I use to be able to put my hand over a 2" vent line and give you a good answer. That was back when we'd do tests with the open ended orifice and manometer.

 

[muli]

Thank you David, but assuming you don´t have a recording gauge how could you guess or know if a particular pumped well is capable to produce enough gas through a pressurized annulus to run a gas engine? I mean, before you commit yourself ordering an engine without knowing if you have enough gas production to run it.

 

[muli]

Thank you also dcasto and I wished I had a hand like yours, as I wished to have a nose like some wine connaiseurs. My concern is really that, guess somehow if a particular pumped well is suitable to a gas engine as prime mover. If I´m not mistaking, I was told or read in the past that someone could guess a gas rate by the length of a burning gas flame, provide you knew the size of the discharge pipe. Is that possible? All I need is a rough guess.

 

[zdas04]

You can purchase a recording electronic gauge that will nearly fit in a shirt pocket for about $400 USD.

Your fundamental problem is one that has existed in pumped wells for decades. The gas flow in the annulus is dominated by the liquid level above the pump, so any pre-pumping gas-flow test you run will not accurately represent the gas available. The nearly universal solution is to set a propane tank to pump the well down some and then try the annular gas. If there is enough then you can redeploy the propane tank. If there isn't enough then you have to decide if the well can tolerate the cost of propane.

David

 

[muli]

OK David, my problem is not so difficult because the wells are already operating with sucker rods and the annulus is bypassed to the flowline. I would appreciate any advising from you to buy one of this electronic handheld devices. The engines I´m looking for require something like 50 to 60 thousand SCF of gas per day

 

[dcasto]

wow, 300HP engines????? maybe you mean 5 or 6 thousand?

 

[zdas04]

dcasto,
I can't find the reference to 300 hp engines above. What am I missing? 50 MSCF/day from 0 psig to 50 psig is 100 hp/MMCF or 5 hp. 50-60 MSCF/d of fuel use is a pretty big load (maybe 300 hp, is that what you're talking about?), but not outrageous.

David

 

[dcasto]

the engines require 50 MCFD. 1 HP uses 8 cf per hour. A CAT 3516 uses 260 MCFD of lean gas, not 1400 BTU/CF casinghead gas.

 

[zdas04]

Maybe his total load is more than just a rod pump? Or maybe it is a REALLY BIG well with a REALLY Deep pump? How about an oil transfer pump? Air Conditioning for the dog house? Free gas taps that have to be compressed at his expense? A safety factor?

Anyway, the 8 cf/hp-hr is an ok number for a small rich burn engine (I think Arrow calls it 9 on the 330, Ajax under part load is closer to 12, but the 8 number shows up pretty often). A big lean burn like the Cat 3516 LE is closer to 6 cf/hp-hr.

David

 

[dcasto]

A lot of stars, but I still don't know if we have really helped anyone, yet.

 

[muli]

Sorry folks, but it was my fault, my mistake. Engine consuption is 5 to 6 MSCFD

 

[dcasto]

here is a simple look. 6000 SCFD is 6000/1440 = 4.1 CFM. A 2 inch line has an area of .026 square feet. so the velocity will be 158 feet/min or 1.8 miles per hour.

Look at a Beufort wind scale, it says 2 miles per hour, it says a wind vane will not move much.

For 60 MCFD, the velocity will be 18 miles per hour and small trees will move.

A $40 aneometer can go a long way.

http://www.dasdistribution.com/products/anemometers/index.htm