Summary
Liquid loading is a serious problem in areas where gas fields are maturing.
This paper presents an analysis of the production behavior of liquid-loaded
wells over time. This clearly shows that these wells can operate at two
different rates—a stable rate, at which full production is taking place, and at
a lower metastable rate, at which liquid-loading effects play a role.
A model has been constructed that enhances the understanding of the process
of water buildup and drainage in gas wells. It assumes a single gas- and
water-coproduction point and a single water reinjection point. As expected, a
water column is built up in the well as soon as production takes place below
the critical rate. As observed in the field, for good inflow performance, a
metastable flow rate can be observed. At this state, the water-reinjection and
water-coproduction rate are equal to one another, and the water-column height
stabilizes.
A sensitivity analysis has been carried out to determine how well parameters
influence the metastable flow rate, the time required to reach this metastable
rate, the corresponding water-column height, and the shut-in time required to
drain this water column. The results of the analysis indicate that significant
metastable flow rates occur in wells that have good inflow performance, a low
water/gas ratio, and a large distance between injection and production
point.
Furthermore, a steady-state analytical solution has been derived for the
metastable rate and stabilized water-column height confirming the
numerical-analysis results.
Introduction
Many of the mature offshore gas fields in the southern North Sea have
already experienced considerable pressure depletion resulting in significantly
reduced gas flow rates and, eventually, liquid loading. Insight into the flow
characteristics of these liquid-loaded wells will help manage tail-end
production (i.e., will help define the most effective means of accelerating and
maximizing their ultimate recovery.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
30 May 2005
- Meeting paper published:
6 September 2005
- Revised manuscript received:
1 March 2006
- Manuscript approved:
3 March 2006
- Version of record:
20 November 2006
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