Gas well deliquification using PCP
Gas well deliquification using PCP
(OP)
Gents,
further to my message about the PCP trial to dewater a gas well, here are some more information:
Reservoir: Gas
Perf. Depth: 1714,5-1717,5 m
Static fluid level: 200m
Expected gas production @ 1200-1400m dynamic fluid level
Gas Prod.: 700scbm/d
WaterProd expected.: 50cbm/d
Pump depth 1680m
H2S: 0
CO2 0,1%
Installed PCP: NTZ350*200*ST25
Rotor: P6
Stator(elastomer) HNBR01
The PCP was installed twice and failed after couple of days operation due to parted rotor @ 150 rpm. The elastomer was found to have excessively swollen.
Does anybody have experience with this type of gas dewatering and can help us to analyse/discus the problem?
further to my message about the PCP trial to dewater a gas well, here are some more information:
Reservoir: Gas
Perf. Depth: 1714,5-1717,5 m
Static fluid level: 200m
Expected gas production @ 1200-1400m dynamic fluid level
Gas Prod.: 700scbm/d
WaterProd expected.: 50cbm/d
Pump depth 1680m
H2S: 0
CO2 0,1%
Installed PCP: NTZ350*200*ST25
Rotor: P6
Stator(elastomer) HNBR01
The PCP was installed twice and failed after couple of days operation due to parted rotor @ 150 rpm. The elastomer was found to have excessively swollen.
Does anybody have experience with this type of gas dewatering and can help us to analyse/discus the problem?





RE: Gas well deliquification using PCP
RE: Gas well deliquification using PCP
I would first look at getting the pump below perfs. If not possible a gas anchor would be beneficial.
Also because of the depths, I would seriously consider a Beam Pumping system.
RE: Gas well deliquification using PCP
One thing I would strongly agree with is the need to get the pump intake below the perforations to minimize the gas coming through the pump. Running the intake above the perfs will result in significant free gas inflow and will reduce the pump efficiency resulting in additional heat that must be dissipated by what will also be reduced mass flow do to the inefficient operation. If the pump begins to heat up then the torque will increase and in the absense of poor lubrication it can be quite severe. Was there any particular reason for landing the pump above the perfs?
With regard to your failure in these dewatering applications rod problems are quite common due to underestimating of the friction as well as harmonics that often occur due to stick and slip in the pump especially if it is not operating fast enough (my experience is that low speeds are bad here and that you want to be in the 150 to 250 RPm range) and if the rotor/stator fit is too tight due to swell or heat generation. You mention you had a rotor failure which is unusual as normally the rod string is the weak point. Was this rotor failure at the connection, near the top in the profile or elsewhere such as in a weld? If near the top it may be from improper space-out (either too high or too low, this can usually be determined in a post inspection of the rotor and stator). If in the connection or at a weld may be due to high torques due to what you indicate was excessive swelling. Elastomer swell in dewatering applications is usually not a problem unless (1) the wrong elastomer is chosen and the temperature are high enough to escalate the water swell or (2) you are seeing explosive decompression effects from the CO2 and CH4. A detailed pump inspection can quantify the extent of the swell and isolate whether it was due to the fluid or the gas. According to your information you ran a hydrogenated nitrile elastomer which is not the normal choice for dewatering or any PCP application for that matter except where there is H2S or high temperatures (above 100C). I don't have any specific experience with that particular elastomer to know how it would react to water but normally in these dewatering applications With you are best to stick to a low ACN nitrile to minimize the water swell.
If you want to provide answers to the questions above as well as some insight on your downhole temperature, casing size, rod string size and operating speeds I might be able to share some more specific experience.
Lonnie