6 replies to this topic

[FacilitiesEng]

Dear All

Currently we are having a problem with our existing water injection pump. The existing pump can only deliver up to 25,000 bbl/day at 2100 psig.

One of our well are having a problem with the its permeability that requiring higher perssure in order to fracture it. The new required pressure is at a min 2700 psig to 3000 psig. Therefore, the existing pump was not able to cater with the new requirement.

New direction has been made by installing new pump for the dedicated problematic well. The new requirement for the dedicated pump is :-
Discharge Pressure :3000 psig@5000 bbl/day
Liquid : Treated Sea water
Location : Offshore Platform
Space : Space are very limited. Dect extension required for the new unit. Plan for the new unit to be temporarily install & commission on top of the deck.

Currently I only have 2 quotation for the above proposal. The quotation are :-

1. 10 Stages Multistage Horizontal Centrifugal Pump
Flow Rate : 146 GPM (5000 bbl/d or 33 m3/hr)
Head : 2243 feet (684 m)
Suction Pressure : 2000 psig
Discharge Pressure : 3000 psig
NPSHr : 9 feet
Design Efficiency : 57%
Design BHP : 149 HP
EOC HP : 214 HP
Driver : Diesel Engine 254 HP (Intermittent)@2300 RPM
Source of water (Suction Side) : From discharge side of the existing water injection pump

2. Reciprocating Pump
Type : Single Acting Triplex Plunger Pump
Rated Pressure : 3030 psi Max. Operating Pressure
Inlet Pressure : Min. 15-20 psi
2.75" Diameter Plungers, Tungsten Carbide Coated
Flow Rate : 131 GPM @ 260 RPM
Driver : Diesel Engine CAT 3406 325 HP@ 1800 RPM
Source of water (Inlet) : From the suction side of existing water injection pump

What was happening in my mind was I do not know which one to choose. Appreciate if any of you guys could give some advice on the pump selection either opt for centrifugal pump or reciprocating pump.


Thanks

Cheer

[Art Montemayor]

Facilities:

I just got through applying several high pressure, 10-stage, produced water injection pumps – one 2,000hp and two 7,000hp each. These were driven by electric induction motor-VFD-gear box. It may be my bad calculations and my increasing senility, but I have several comments/questions on this application:

1) You are on an offshore platform, so space & volume are a premium. Yet you are evaluating the replacement options differently: a) the second centrifugal pump is just that – it is a pump in series with the existing and, therefore, takes up additional space. b) the triplex pump is a "stand-alone" – it replaces the existing centrifugal. This doesn't seem equitable for economic and engineering evaluation.

2) You say that option (a) has a TDH ("Head") of 2,243 feet; the differential pressure is 1,000 psi (3,000 – 1,000psig) but my calculations show that 1,000 feet of salt water (Sp. Gravity = 1.024) is equal to 2,255 feet, not 2,243 feet. This is minor, but maybe my calcs are wrong. However, you are proposing to apply a TDH of 3,000 psi (7,665 feet of head) to the triplex.

3) Are you unable to put a triplex in series with the existing centrifugal? Is the suction pressure rating on the triplex too low? Operating a PD on the discharge of a centrifugal is much easier operationally than two centrifugals in series, in my opinion. And if you have the space, this would be my first option.

4) The water hp for case (a) = (1.024) (150 gpm) (2,255 ft)/(3960) = 87.5 hp (@ 100% eff.). At 57% efficiency, this = 87.5/0.57 = 153.5 hp (close to the design 149 hp).

5) If the triplex is run in series, it needs less hp for the same 2,255 ft of TDH due to its much higher efficiency (approx. 90%). Also, the wear and maintenance will be much less.

For the relatively low flow rate of 150 gpm, the positive displacement triplex seems to me to be the practical and economical (on operating costs) choice. However, the capital costs may override the operating advantage. You are the only one who knows this.

One last item: the length – or duration of service – may be a strong factor on the final selection. If you are going to operate this field for 5 years or 15 years might have a bearing on the decision.

[FacilitiesEng]

Facilities:

I just got through applying several high pressure, 10-stage, produced water injection pumps – one 2,000hp and two 7,000hp each. These were driven by electric induction motor-VFD-gear box. It may be my bad calculations and my increasing senility, but I have several comments/questions on this application:

1) You are on an offshore platform, so space & volume are a premium. Yet you are evaluating the replacement options differently: a) the second centrifugal pump is just that – it is a pump in series with the existing and, therefore, takes up additional space. the triplex pump is a "stand-alone" – it replaces the existing centrifugal. This doesn't seem equitable for economic and engineering evaluation.Initially we plan to operate the PD pump at the discharge of the existing water injection pump but since the pressure (up to 2100 psi) found to be too high for pump inlet we had decided to install it at the suction of the existing water injection pump. In other word, for option (a) the centrifugal pump will be install in series and act as the booster pump. For option ( the PD pump will be install in parallel to the existing pump and they are sharing the common suction.

For the space, we will gonna have some deck extension in the near future or we could bear with the temporary installation (on top of the deck) until the rental of the platform expired within 3 years from now. At that time, we should have our own platform (FEED for the new platfrom - ongoing).

For power generation, the platform have 4 unit generator (diesel engine driven). Due to the high power consumption, we opt (for both option) the be drive by diesel engine instead of electric motor. So the space requirement for both option are quite the same (I think). FYI, currently we rent 2 units of High Pressure (Single Acting Triplex Plunger pump) for the dedicate problematic well. Once we procure the new pump (either option (a) or () we will replace the rented unit with the new one (a or . The space usually used for loading and well intervention activity i.e wireline unit. Do you think that centrifugal pump could be suitable to operate in that space when compared to PD pump?

2) You say that option (a) has a TDH ("Head") of 2,243 feet; the differential pressure is 1,000 psi (3,000 – 1,000psig) but my calculations show that 1,000 feet of salt water (Sp. Gravity = 1.024) is equal to 2,255 feet, not 2,243 feet. This is minor, but maybe my calcs are wrong. However, you are proposing to apply a TDH of 3,000 psi (7,665 feet of head) to the triplex.

3) Are you unable to put a triplex in series with the existing centrifugal?YES..discharge pressure is too high for inlet of the PD pump. Is the suction pressure rating on the triplex too low? Inlet connection for triplex - 6" CL 150# RF. Operating a PD on the discharge of a centrifugal is much easier operationally than two centrifugals in series, in my opinion. And if you have the space, this would be my first option.You said to operate the PD on the discharge of a centrifugal..what if operate the PD on the suction of the centrifugal?

4) The water hp for case (a) = (1.024) (150 gpm) (2,255 ft)/(3960) = 87.5 hp (@ 100% eff.). At 57% efficiency, this = 87.5/0.57 = 153.5 hp (close to the design 149 hp).

5) If the triplex is run in series, it needs less hp for the same 2,255 ft of TDH due to its much higher efficiency (approx. 90%). Also, the wear and maintenance will be much less.

For the relatively low flow rate of 150 gpm, the positive displacement triplex seems to me to be the practical and economical (on operating costs) choice. However, the capital costs may override the operating advantage. You are the only one who knows this.We have two quotation and the cost for the option (a) is a bit higher than option (. I am not sure the operating and maintenance cost for the both options.

One last item: the length – or duration of service – may be a strong factor on the final selection. If you are going to operate this field for 5 years or 15 years might have a bearing on the decision. Duration of the service is 3 years.

[/color]Dear 'Art Montemayor'

Thanks for your fruitful reply. Please find my comments in [color="#0000FF"]blue.


When you talk about VFD, thats trigger me something that currently happening on the existing water injection pump. Since the source (water) for the rental unit was tapped from the suction of the existing water injection pump (sharing the common line), the existing pump have experienced multiple tripped due to VFD failured. Is it because we are sharing the common suction which cause the pump to cavitate? FYI the suction line pressure is 7.7 bar@rated 168m3/hr.

[Dexco]

Typically if you are unsure of what pressures you may encounter in the future it is better to stick with a Multiplex pump, the multistage centrifugal works off of a pump curve the more pressure you have the less flow will be pumped, and you are restricted to the small variance in the curve. But with a positive displacement pump you are allowed "X" amount of discharge pressure whether you are pumping 6,000BBL or 20,000BBL. Meaning you will never lose your flow rate with a triplex pump, as presure comes up .

I have 4 W-2250 pumps (see attached spec sheet) in stock that will pump 25,000 BBL/day @ approx. 3000 PSI up to 4,000 PSI intermittent no problem. We can have it accept the 2000 PSI inlet pressure as well, requiring approximately 475HP to run. Or to reduce the footprint further you can remove the existing pump and us ethe triplex to pump the entire flow with approx. 20 PSI inlet pressure. These W-2250's are relatively a small footprint compared to a lengthy multistage centrifugal(s) that you would need to achieve the same flow and pressure. We have a large stock of pumps that will cover the 3000 PSI and 5000 BBL/day application.
Dexco has produced numerous small footprint packages that are "air frieght friendly" Specially built for offshore rig applications. Multistage centrifugals are nice pumps to have but they do not always perfectly suit the application.

Dexco International is a Distributor for National Oilwell Varco pumps as well as Borets-Weatherford HPS and ESP pumps. We stock pumps from 2-2250HP and our complete turnkey packaged pumps are ready for shipping in 2-4 weeks. Guaranteed.

check out our website for more information on what we do. www.dexcointernational.com

Steven
Phone: 1-403-896-9444

Attached Files

•  W2250.pdf   303.98KB   94 downloads

[Dexco]

When you talk about VFD, thats trigger me something that currently happening on the existing water injection pump. Since the source (water) for the rental unit was tapped from the suction of the existing water injection pump (sharing the common line), the existing pump have experienced multiple tripped due to VFD failured. Is it because we are sharing the common suction which cause the pump to cavitate? FYI the suction line pressure is 7.7 bar@rated 168m3/hr.
[/quote]
It is not good practice to run a multistage centrifugal off of any common line with a PD pump Suction or Discharge. The pulsations in the line are too much for a typical multistage pump to handle and will definetly have an outcome on your electrical system. Imagine every little flutter of pulsation going into the multistage to be compensated by the VFD. I have seen this scenario before. The HPS or "multistage" pump had to have it's own piping that was not shared with the PD pumps in the plant. Also a PD pump should be fed with 1.5 times the flow rate to reduce pulsation in the suction line.

Attached Files

•  DEXCO_WEATHERFORD_Brochure.pdf   361.33KB   87 downloads

[FacilitiesEng]

Typically if you are unsure of what pressures you may encounter in the future it is better to stick with a Multiplex pump, the multistage centrifugal works off of a pump curve the more pressure you have the less flow will be pumped, and you are restricted to the small variance in the curve. But with a positive displacement pump you are allowed "X" amount of discharge pressure whether you are pumping 6,000BBL or 20,000BBL. Meaning you will never lose your flow rate with a triplex pump, as presure comes up .

I have 4 W-2250 pumps (see attached spec sheet) in stock that will pump 25,000 BBL/day @ approx. 3000 PSI up to 4,000 PSI intermittent no problem. We can have it accept the 2000 PSI inlet pressure as well, requiring approximately 475HP to run. Or to reduce the footprint further you can remove the existing pump and us ethe triplex to pump the entire flow with approx. 20 PSI inlet pressure. These W-2250's are relatively a small footprint compared to a lengthy multistage centrifugal(s) that you would need to achieve the same flow and pressure. We have a large stock of pumps that will cover the 3000 PSI and 5000 BBL/day application.
Dexco has produced numerous small footprint packages that are "air frieght friendly" Specially built for offshore rig applications. Multistage centrifugals are nice pumps to have but they do not always perfectly suit the application.

Dexco International is a Distributor for National Oilwell Varco pumps as well as Borets-Weatherford HPS and ESP pumps. We stock pumps from 2-2250HP and our complete turnkey packaged pumps are ready for shipping in 2-4 weeks. Guaranteed.

check out our website for more information on what we do. www.dexcointernational.com

Steven
Phone: 1-403-896-9444

Dear Steven

That was quite an interesting info though..I believe I could get a proposal from you then. OUr requirement is as per below :-


Pump Flowrate : 5000 bbl/day
Pump Type : Centrifugal or Reciprocating (whichever more suitable)
Discharge Pressure : minimum 2700 psig
Suction Source : 1. Common suction line of the existing Water Injection Pump (Multistage pump) - Pressure at 7.7 barg (112 psig).
OR
2. Discharge of the existing water injection pump - Pressure at 2000 psig
Driver Unit : Diesel Engine
Operating Philosophy : 24 hrs running - Portable Unit - due to space constraint.
Load Capacity : Below 200 lb/ft2


Please provide me your email add.

[Dexco]

For now use pumps@dexcointernational.com I will give you my correct e-mail once you reply to it.

Steven