Gas lift design philosophy for chevron s subsea developments
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Gas Lift Design Philosophy for Chevron’s Subsea Developments. Shauna Noonan, Completions Engineering Team Chevron Petroleum Technology Company Houston, Texas. The Challenge. “Size the downhole orifice as big as possible and we can just control the gas injection rates from the FPSO”

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Gas Lift Design Philosophy for Chevron’s Subsea Developments

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Gas lift design philosophy for chevron s subsea developments

Gas Lift Design Philosophy for Chevron’s Subsea Developments

Shauna Noonan, Completions Engineering Team

Chevron Petroleum Technology Company

Houston, Texas


The challenge

The Challenge...

“Size the downhole orifice as big as possible and we can just control the gas injection rates from the FPSO”

- general comments heard from various Chevron engineers

  • THE DOWNHOLE CHOKE (aka orifice) CONTROLS THE RATE OF GAS INJECTION INTO THE TUBING, NOT THE SURFACE CHOKE!!!!!!!!


The challenge1

The Challenge..

“If this stability issue exists, then how come I don’t see this with my platform wells?”

- general comments from various Chevron engineers

Answer: Turns out they are not continuously injecting through the orifice. As these platform wells are completed with a conventional design (unloading valves), the well instability is dampened due to multipointing.


Predicting stability margins with transient programs

Predicting Stability Margins with Transient Programs

OLGA is the primarily tool used within the industry for transient analysis, however it does not look at transient behavior between the surface and downhole injection chokes. DynaLift addresses the gas lift transient issue, but does a poor job of the flowline assessment. Hence, Chevron has to use both programs….

Flowline/ Riser stability OLGA

Gas Lift stability DynaLift


Gas lift design philosophy for chevron s subsea developments

OFFSHORE ANGOLA:

Kuito and Benguela-Belize-Tomboco


Gas lift design philosophy for chevron s subsea developments

Kuito 1A


Gas lift design philosophy for chevron s subsea developments

unstable


Gas lift design philosophy for chevron s subsea developments

U-tube effect


Gas lift design philosophy for chevron s subsea developments

THE CHALLENGE …..

“In order to prevent erosion to the orifice, let’s run two of them. Have the upper orifice the “operating point” and then run a REALLY large unloading orifice below it!”

- comments made by the reservoir engineering staff working on the project


Gas lift design philosophy for chevron s subsea developments

LOWER “UNLOADING” ORIFICE

UPPER “OPERATING” ORIFICE

WHY THIS IDEA WILL NOT WORK ….


Kuito update

Kuito Update

  • Field start-up Jan 2000

  • Gas Lift injection began May 2000

  • Serious Problems with Flowline Stability

  • Engineering currently working on next 11 producers ….. Completed field testing to calibrate Olga model and the engineers using Olga and Dynalift are working as one “unit”.


Gas lift design philosophy for chevron s subsea developments

BENGUELA-BELIZE-TOMBOCO PROPOSED DEVELOPMENT

- ONLY SUBSEA WELLS EXPECTED ARE 2 WATER SOURCE WELLS EACH SUPPLYING 40,000 BWPD


Gas lift design philosophy for chevron s subsea developments

BBT team wanted to lift 40,000 bwpd using gas lift


Gas lift design philosophy for chevron s subsea developments

EAST COAST CANADA: HEBRON


Hebron artificial lift study

HEBRON ARTIFICIAL LIFT STUDY

  • DETERMINE METHOD OF LIFT (ESPs or GAS LIFT)

  • 1870 m TVD, 21 API, 50 m3/m3

  • Emulsions / Hydrates serious issues

  • Front-End engineering only concerned with horsepower / production relationship …. not stability

  • Used both static (for emulsions) and transient programs for the gas lift portion.


Gas lift design philosophy for chevron s subsea developments

SAMPLE CURVE FROM HEBRON


Gas lift design philosophy for chevron s subsea developments

Example: Effect of Wellbore Step Out

For every set of conditions, an optimum and maximum case was done


Gas lift design philosophy for chevron s subsea developments

EFFECT OF WATERCUT / WELLHEAD PRESSURE FOR ALBA

700 PSI

500 PSI

750 PSI

700 PSI

500 PSI

750 PSI

Pr=3200 psi

Pr=2800 psi

0%

40%

95%

0%

40%

95%


Gas lift design philosophy for chevron s subsea developments

EXISTING SUBSEA GAS LIFT COMPLETION THAT CHEVRON DOES NOT RECOMMEND!!

“the name / location has been removed to protect the innocent”

  • 16/64th valve

  • 20/64th valve

  • 28/64th valve

  • DUMMY VALVE !!

Available gas injection pressure = 1300 psi from 3500 m away

In addition, the “flow conduit” ID goes from 3.5” (gravel pack completion) to 9 5/8” (for 700 m / 2300 ft) to 4.5 (upper completion)


Thank you for listening

Thank You For Listening

Chevron’s World of Artificial Lift

North Sea

(ESP/GL)

Canada

(PCP/GL/BP/ESP)

USA

(PCP/GL/BP/ESP/JP)

Kuwait

(PCP)

China

(ESP/GL)

Thailand

(GL)

Nigeria

(ESP/GL)

Venezuela

(BP/ESP/PCP)

Indonesia

(ESP/BP/PCP/GL)

Colombia

(PCP)

Angola

(GL/PCP/CTESP)

Australia

(GL/BP)

Argentina

(BP/ESP/ GL)


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