I have a chart from a gas lifted well. Checkout the behaviour and tell me what you think is causing it. I know its switching between valves but it only does this at low gas lift system pressure.
Thanks,
S.
Originally Posted by Eng.Koriesh
i think at low gas what happens that a deeper valve is not completely open , probably causing the gas coming into annulus to be less than gas coming out of annulus , which cause pressure build up in the annulus , to extent that open a shallower valve that time more gas come into tubing causing flow of higher rate and increase in well head pressure . the opening force in the shallower valve comes from the tubing pressure and annulus pressure , the low flow rate and low injection rate of gas caused a high tubing pressure in front of valve orifice so the valve opens in the low rate , in the high injection rate surging is less because deeper valve is completely open and handles the designed injection rate and hence cause tubing pressure to be low in front of the shallower valve and hence the valve is kept in close position .. then the rate of injection gas coming into annulus is equal to that leaving annulus through orifice . hence no surging is seen .
It sounds good to find such analysis of gas lift chart as it happens now on this page, as continious disscussion in this regard, let me say that Mr. Kourish just said " Surging is rare to happen in case of higher gas lift injectiion rate" ,
His comment is right but surging may happen where there is a high gas lift injection pressure, the deepest valve may face a problem of incapability of handeling such high gas lift rate, in turn the gas lift downstream pressure " the annulus pressure" will increase which in turn may open the shallower valve and that point the well will face a problem of fluid surging and the same sequence of surging will occur as it is for low gas lift pressure.
Let me explain in details: with the higher gas lift pressure, the gas lift rate will increase as well, and if this gas lift rate comes to a point that the deepest valve couldn't handle, so there will be a back pressure in the annulus will appear which in turn will be a back pressure exereted on the shallow valve and this may reach to open it and this will lightening the liquid coming up in the tubing and may reach to a very low gradient (High GLR) which will increase the friction losses and in turn will force the fluids to fall back in the tubing then the shallow valve will close and the deeper still injecting the highest gas rate that can be handeled through it (as the gas lift injection pressure high), and the same phenomenon will repeat all the time without any fluids being produced at surface or may mist flow will be seen at surface (you can say, no fluids coming out of the well)
Finally, i want to ascertain that well surging is common in each two cases (high gas lift pressure or even low gas lift pressure)
Originally Posted by Eng.Koriesh
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