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”
Gas Lift Design Philosophy for Chevron’s Subsea Developments
Shauna Noonan, Completions Engineering Team
Chevron Petroleum Technology Company
“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
“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.
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
Kuito and Benguela-Belize-Tomboco
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
LOWER “UNLOADING” ORIFICE
UPPER “OPERATING” ORIFICE
WHY THIS IDEA WILL NOT WORK ….
BENGUELA-BELIZE-TOMBOCO PROPOSED DEVELOPMENT
- ONLY SUBSEA WELLS EXPECTED ARE 2 WATER SOURCE WELLS EACH SUPPLYING 40,000 BWPD
BBT team wanted to lift 40,000 bwpd using gas lift
EAST COAST CANADA: HEBRON
SAMPLE CURVE FROM HEBRON
Example: Effect of Wellbore Step Out
For every set of conditions, an optimum and maximum case was done
EFFECT OF WATERCUT / WELLHEAD PRESSURE FOR ALBA
EXISTING SUBSEA GAS LIFT COMPLETION THAT CHEVRON DOES NOT RECOMMEND!!
“the name / location has been removed to protect the innocent”
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)
Chevron’s World of Artificial Lift