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TUALP Abstract
 

Maria M. Tinoco (Master of Science in Petroleum Engineering)
Validation and Improvement of Stability Criteria for Gas-Lift Wells
(147pp.- Chapters VII)
Directed by Dr. Dale Doty and Dr. Stefan Miska
(206 words)

This study validates and improves Alhanati' s stability criteria for gas-lift wells. Field data gathered from 25 unstable wells from Lake Maracaibo, Venezuela, support the conclusion that Alhanati's stability criteria are unable to accurately predict instability when the gas-lift valve operates in the throttling critical flow regime.

A new stability model was developed for gas-lift wells. The model properly takes into account the gas-lift valve throttling flow regime by including the friction component in the tubing pressure gradient calculation, and by developing new equations for Kvt and Kve which describe the behavior of the gas-lift valve. The new model exhibited dramatically improved accuracy in predicting the stability of the 25 wells.

Hypothetical studies were performed to analyze conditions not covered by the range of the field data. It was found that the predicted stability behavior can be significantly influenced by the surface injection choke flow regime, especially when the gas-lift valve is operating in the subcritical flow regime.

A sensitivity analysis was performed which showed that some variables influence a well's stability more than others, depending on the operating valve's flow regime. This study supports the conclusion that both the gas-lift valve and surface choke flow regimes must be considered to accurately predict a gas-lift well's stability.

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Last updated September 04, 2012