Summary
The Cannonball field is a 1 Tcf gas/condensate development offshore Trinidad
producing at a sustained rate in excess of 800 MMcf/D from three wells. The
completion design selected was 7⅝-in. production tubing with an openhole gravel
pack. The initial well (CAN01) has produced at 333 MMcf/D. These rates are
higher than typically experienced, which has raised concerns about the
resultant potential for metal erosion. As a result, a rigorous erosion study
was initiated. The objective was to evaluate erosion quantitatively at various
rates over the life cycle of the well to design the completion appropriately
and select the appropriate materials.
The erosion nodes within the completion--changes in flow direction (e.g., a
tee such as in the wellhead) and/or flow constrictions--were identified as the
tree, a landing-nipple profile near the surface, and a formation-isolation
device (FID) positioned in the gravel-pack assembly. The key parameters were
defined as particles of sharp sand, with a diameter of 50 μm, at a
concentration of 0.1 lbm/MMcf. Erosion rates were calculated using the erosion
model, Sand Production Pipe Saver (SPPS), developed by the Erosion/Corrosion
Research Center (E/CRC) at the University of Tulsa, USA. Erosion rates were
calculated over the life cycle, starting at initial rates of 280 and 400
MMcf/D. Erosion rates were also calculated with and without a liquid film (a
protective layer on the pipe wall that can reduce the erosion rate). Erosion
results (without a liquid film) at all nodes exceeded BP's erosion limit;
however, the erosion results with a thin liquid film were mostly below the
company's erosion limit. Determination of the presence and thickness of the
liquid film was critical. A multiphase-pipeline simulation calculated that a
sufficient liquid film would exist at all critical areas. Erosion of the tree
was assessed further by computation-fluid-dynamics (CFD) models, which
identified several hot spots; thus, additional cladding of all flow-wetted
surfaces and rounding of the outlet corner was required. The Cannonball
completion design, including the tree, was determined to be capable of
sustained rates up to a maximum of 400 MMcf/D. The three-well development,
where initial rates have been as high as 333 MMcf/D, has been on production for
several years without any erosion issues.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
7 July 2008
- Meeting paper published:
21 September 2008
- Manuscript approved:
15 July 2009
- Published online:
21 January 2010
- Version of record:
11 March 2010
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