Summary
Over 28 production well tests and two interference tests have been conducted
in the Albertine Graben basin in Uganda since the first oil discovery in 2006.
The Uganda crude is moderately viscous, and low-gas/oil ratio (GOR), and later
discoveries were mostly in shallow lower-energy systems. In addition, Uganda
crude has relatively high pour points and wax appearance temperatures (WATs),
which result in flow-assurance challenges during production testing operations.
Production challenges brought about by the low energy scenario are offset by
high formation permeability (mostly in the multidarcy range).
Field X was discovered in 2008 by Well X-1, and subsequently appraised by
several wells. Zone 1 of Well X-1 was production tested under natural flow
without a rig. Although hydrocarbons were brought to surface successfully
during the testing operation, the maximum flow rate achieved was approximately
262 BOPD, and a stable flow rate could not be sustained. Fluid-segregation
effects distorted the early-time data. In addition, flow-assurance challenges
prevented acquisition of late-time response from the pressure buildup (PBU).
Therefore, important dynamic information, particularly in regard to flow
barriers, was not obtained.
A change in completion philosophy was proposed after detailed analysis of
the test results. Well X-1 was retested with a new completion design
incorporating real-time surface-readout (SRO) pressure and temperature
monitoring capability, a hydraulically controlled inflow control valve (ICV), a
progressing cavity pump (PCP), and a surface-controlled electrical heat trace
system. High-quality well-test data was acquired, and the real-time data was
used extensively throughout operations to optimize flow and buildup periods and
well operating envelopes. Several challenges were faced during the first
completion run, leading to the use of the contingent insert PCP system to
retest Zone 1.
This paper highlights the first application of a PCP completion in Uganda
and describes the challenges faced during the completion and well-testing
operation. The experience from Well X-1 has demonstrated that high-quality
exploration and appraisal well-test data can be acquired using a PCP
completion. Similar well-completion designs will be used in Uganda for
appraisal of other discoveries.
© 2013. Society of Petroleum Engineers
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History
- Original manuscript received:
9 June 2012
- Meeting paper published:
8 October 2012
- Revised manuscript received:
24 October 2012
- Manuscript approved:
5 November 2012
- Published online:
22 January 2013
- Version of record:
26 February 2013
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