Summary
In this paper, we present a field example where pressure and
distributed-temperature measurements enabled understanding of reservoir
characteristics and fluid movement causing production hindrance in an offshore
horizontal well. The field example has a horizontal well in the South China Sea
that was completed as an openhole monobore oil producer using a slotted liner.
The well began production with an initial oil rate of 1,800 B/D. Oil production
quickly dropped to 1,000 B/D and gradually declined to 200 B/D. During this
period, the gas/oil ratio (GOR) steadily increased from 200 scf/bbl to 2,200
scf/bbl. To arrest production decline, a chemical treatment was conducted to
remove suspected emulsions and polymers assumed to have been depositedduring
drilling. Immediate post-treatment production increased to 3,700 B/D, but
dropped dramatically and stabilized at pretreatment rates soon after. Formation
of emulsions and asphaltenes were believed to be the cause of the production
decline. However, with inadequate information, the diagnosis was inconclusive.
Consequently, another chemical treatment was conducted and this time a
fiber-optic-enabled coiled-tubing (CT) string along with real-time
bottomhole-pressure and temperature gauges were used to acquire distributed
temperatures and pressures of the entire horizontal section of the
wellbore.
Results of the pressure survey revealed that the well was receiving
insufficient pressure support from the water injector, which was causing
gas-cap expansion. The distributed-temperature survey indicated excessive gas
production from the toe of the horizontal section as a result of this
expansion, thus limiting liquid production. The combination of gas rates with
oil and water production has also created tight emulsions, further hindering
production performance. It was concluded that the high gas production from the
toe could not be selectively shutoff or controlled in the horizontal openhole
slotted-liner completion to perform an effective stimulation program and treat
the tight viscous emulsions.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
3 February 2009
- Meeting paper published:
31 March 2009
- Revised manuscript received:
12 August 2009
- Manuscript approved:
25 August 2009
- Published online:
11 March 2010
- Version of record:
11 May 2010
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