Field Evaluation of an Offshore Pumping System

Field Evaluation of an Offshore Pumping System

Jeffrey A. Bennett1, Augusto Garcia-Hernandez1, Marco Antonio Muñoz Prior2

Moisés León Dorantes2, 1 - Southwest Research Institute®

2 - PEMEX Exploración y Producción

Jeffrey A. Bennett (Presenter)• Research Engineer, Southwest Research Institute• Experienced in thermal fluid network modeling• MSc – Turbomachinery Aeromechanics, KTH/Université de Liège • BS – Mechanical Engineering, Virginia Tech

Augusto Garcia-Hernandez• Group Leader, Pipeline Simulation, Southwest Research Institute• 12 years experience modeling pipelines and associated machinery• MS – Petroleum Engineering, University of Tulsa• BS – Mechanical Engineering, Universidad Central de Venezuela

2/22-25/2016 Field Evaluation of an Offshore Pumping System 2

Slide 2: Presenter/Author Bios

Marco Antonio Muñoz Prior• Mechanical Engineer Electrician, Design and Optimization of

Crude Oil Infrastructure, PEMEX Exploración y Producción• Mechanical Engineering, Instituto Politecnico Nacional

Moisés León Dorantes• Former superintendent in the Coordination of Transport and Oil

Distribution, PEMEX Exploración y Producción• Mechanical Engineering, Instituto Politecnico Nacional


Slide 3: Presenter/Author Bios

An evaluation was performed on one of the largest offshore facilitiesbelonging to PEMEX Exploration and Production due to forecasts predictingthat future crude oil production will contain heavier oils. The primary functionof the evaluation was to assist PEMEX in determining if the facility’s pumpsneeded to be upgraded. In addition, several of the centrifugal pumps of theplatform had been recently replaced with screw pumps. Therefore, theevaluation was performed in three parts: first, the remaining centrifugalpumps were evaluated in the field at available testing conditions; second, ahydraulic analysis of the network was conducted to predict the systemperformance with heavier oils; and third, an interactive pump simulator wasdeveloped to train operators on the new screw pump equipment. Thispresentation/paper will focus on the first step, the field evaluation of thecentrifugal pumps, and the remaining steps will be discussed briefly.


Short Abstract

Presentation Overview

• Field Evaluation– System Background– Performance Testing

Approach– Pipeline Modeling Results– Field Testing Results

• Hydraulic Modeling• Simulator Development







Background

• PEMEX Exploration and Production’s off-shore pumping system transports approximately 50% of Mexican crude oil production

• Complex interconnected platform network where different crude oils are mixed

• Historically has operated with 19 API oil, however, forecasts predict mixtures of approximately 16 API oil

• Screw pumps recently installed to help transport heavier oil

• Aging centrifugal pumps require a performance evaluation


TERMINAL MARITIMA DOS BOCAS

Cayo Arcas

Rebombeo

FSO Ta’Kuntah

Nohoch-A

POL-A

Akal-N

L-1

L-1

L-4

L-2

L-2

Akal-B

36"

Akal-L

Akal-J

L-2L-1

L-3

ABK-ARMSO

L-3

Akal-C

36"36"

36"36"

36"

36"

24"

24"

30"

20"20"

24"36"

36" 36"

AIKMZ

FPSOYùum

K'ak'náab

36"36"

Rebombeo Platform

• The booster platform “Rebombeo” is located in the Gulf of Mexico approximately 25 miles off-shore

• Two 36-inch sub-sea pipelines travel 52 miles

• Platform has 10 pumps connected in parallel– 6 centrifugal– 4 screw (new)


TB-A TB-C TB-DTB-BTB-01 TB-02 TB-03 TB-04 TB-05 TB-06

LINE 2 INLET

LINE 2 OUTLET

REBOMBEO PLATFORM

LINE 1 INLET

LINE 1 OUTLET

FILTERS FILTERS

CENTRIFUGAL PUMPS

SCREW PUMPS

Performance Testing

• Goal: Traverse entire pump curve at a given speed (follow ASME PTC-8.2 Standard)

• This test requires the system pressure difference to decrease as the flow rate increases

• Platform’s 6 centrifugal pumps come in 2 varieties – high capacity and low capacity

• Can we take advantage of the different pump types?


0

500

1,000

1,500

2,000

2,500

3,000

3,500

0 2,000 4,000 6,000 8,000 10,000 12,000

Hea

d [F

t]

Flow [GPM]

Pump Curves

Low Capacity PumpHigh Capacity Pump

Pipeline System Curves

• Dissimilar to the pump curve, the pipeline system curve requires an increasing pressure difference for high flow rates

• For standard operation this is great -> stable operating point

• For testing a means to vary flow conditions is necessary to follow the testing standard


0

100

200

300

400

500

600

700

800

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Pres

sure

[PSI

A]

Flow [GPM]

Pipeline System Curves

Pipeline to PlatformPipeline from Platform

Sample Test Point

• Pumps are in parallel, thus equal head across each

• Test pump kept at constant speed

• Speed of other pumps varied to change flow through test pump

• Pipeline simulations used to prove approach and determine necessary test conditions


0

500

1,000

1,500

2,000

2,500

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Hea

d [F

t]

Flow [GPM]

Sample Test Point

Test Pump @ 5,200 RPMFlow - Test PumpLow Capacity Pump @ 5,210 RPMFlow - Low Cap. PumpHigh Capacity Pump @ 3,100 RPMFlow - High Cap. PumpHead Level

Pipeline Network and Machinery Model

• 1-D pipeline fluid model of the existing facility including L1, L2, and L3 lines

• Used previous pump field measurements to represent pump curves

• Various emulsion of water-in-oil up to 30% water-cut

• Flow, pressure, and temperature field data was previously used to validate the hydraulic model within 1.12%


REBOMBEO

NH-AAKAL-C

L-1L-2

20” ∅AKAL-J

24” ∅

36” ∅

36

” ∅

L-3

TMDB

INT-26INT-52

INT-27

L= 5.2 km

L= 8.6 km

L= 5.3 km

L-3

Crude Oil Pipeline System from the Production Platforms to TMDB

Modeling Results

• Modeling demonstrated that test approach of varying speed of adjacent pumps is able to vary flow through the test pump

• However, unable to traverse entire pump curve with this approach

• Traverse of entire pump curve requires a change in platform operation conditions

• Limitation primarily due to platform pressure limits


0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Hea

d [f

t]

Flow [GPM]

Predicted Pump Performance

Test RPM - Corrected with Affinity LawsTest RPM - Corrected for ViscosityBEPTest Point 1: 1,846 GPMTest Point 2: 2,615 GPMTest Point 3: 3,650 GPMTest Point 4: 4,600 GPM

Test Set-up: Flow Measurements


Ultrasonic Flow Meter

Test Set-up: Pressure Measurements


Differential Pressure

Suction Pressure Discharge Pressure

Pump Speed

Measured Pump Performance

• Only one platform flow condition available for testing – limited to current production

• Performance test was able to traverse a portion of pump curve

• Results used to estimate the pump degradation

• Testing was performed on 3 of the 6 centrifugal pumps


0

200

400

600

800

1,000

1,200

1,400

1,600

1,800

2,000

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000H

ead

[ft]

Flow [GPM]

Measured Pump Performance

Test RPM - Corrected with Affinity Laws

Test RPM - Corrected for Viscosity

Test RPM - Corrected for Degradation

Test RPM - Corrected for Degradation and Viscosity

Measurements

BEP






Hydraulic Modeling Evaluation

• After performance testing complete, additional simulations performed to predict scenarios that are undesirable for experimentation at an operating platform either due to expense or safety

• Water hammer scenarios used to predict worst-case pressure spikes

• Also simulated changes to system valve configurations


0

2,750

5,500

8,250

11,000

13,750

16,500

19,250

22,000

0

10

20

30

40

50

60

70

80

0 5 10 15 20

Flow

Rat

e (G

PM)

Pres

sure

(Kg/

cm^2

)

Time (min)

SDV-3101closed

Valve beginsclosingValve beginsclosingValve beginsclosing

Valve Closed

Valve Starts to Close






Purpose of Developing a Training Simulator

• Safely train operators to use newly installed screw pumps

• Helps platform operators comply with API 1120, ASME B31Q, RP 1161 and RP T-2


Training on the Simulator

• Simulator has screens that mimic control screens and a computational engine that predicts system response to trainee actions

• Additional screens added to provide operators with insight into the system hydraulics

• Ability to simulate complex procedures such as start-ups and shutdowns


• Field evaluation of offshore pumps was performed

• Pipeline simulations were used to provide insight into test conditions necessary to perform a full sweep of pump curve

• Limited flow conditions in the field resulted in a limited range of the pump curve being tested

• Pump degradation was estimated from the field testing and adopted in the model

• Hydraulic system evaluation used to estimate worst-case water hammer scenarios

• Training simulator was developed to train operators to use newly installed screw pumps


Conclusions

Centrifugal Pump with Shaft Guard On


Thank you for your attention!

I will be happy to address any questions.

Jeffrey A. BennettResearch Engineer

[email protected]

Augusto Garcia-HernandezGroup Leader

[email protected]

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Field Evaluation of an Offshore Pumping System

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