Summary
The critical gas velocity and flow rate for unloading liquids from a gas
well has been the subject of much interest, especially in old gas-producing
fields with declining reservoir pressures. For low-pressure gas wells, Turner's
model (also called Coleman's model) is judged as more suitable for predicting
liquid loading in gas wells. However, field practice proves that there are
still a number of low-pressure gas wells producing without loadup when the
production rate is lower than Turner's minimum production rate.
On the basis of experimental results, a new approach for calculating the
critical gas-flow rate is introduced in this paper, which adopts Li's basic
concepts, while taking into account the impact of the changes of gas-lifting
efficiency caused by the rollover of droplets in the process of rising. A
dimensionless parameter, loss factor S, is introduced in the new model to
characterize the extent of the loss of gas energy.
Well data from Coleman's paper (Coleman et al. 1991) were used in this paper
for validation of the new model. The predicted results from the new model are
better than those from Li's model, and even better than Turner's model. The new
model is simple and can be evaluated at the wellhead when the pressure is less
than 500 psia and the liquid/gas ratios range from 1 to 130 bbl/MMscf, which is
suggested by Turner et al. (1969) to ensure a mist flow in gas wells.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
11 June 2010
- Revised manuscript received:
9 January 2012
- Manuscript approved:
11 January 2012
- Published online:
19 July 2012
- Version of record:
20 November 2012
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