the role of the annular gap in expandable sand screen completions spe 86463. j. heiland, j. cook, a....
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The Role of the Annular Gap in Expandable Sand Screen Completions SPE 86463.
J. Heiland, J. Cook, A. Johnson, B. Jeffryes. Schlumberger Cambridge Research
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Outline
• Where does the gap come from?
• How does it influence the mechanics of the completion?– experiments
– theory
• How does it influence the hydraulics?
• Conclusions.
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Origins of the gap
• State of the hole after drilling (enlargement, tortuosity, rugosity).
• Nature of the screen - expansion ratio.
• Nature of the expansion process - fixed diameter or compliant.
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Possible consequences of a gap: short- and long-term
Rock failure behind screen with gap:
• generating load on screen.
• releasing grains and fines.
– transport, and erosion of screen
– plugging of screen
• changing permeability ( or ).
Fluid flow in annular gap:
• intervention or production logging more difficult.
This paper addresses the first two of these.
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Views of the system
Collapse; closure; inflow
Inflow; fluid and sand transport
Transverse
Axial
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Transverse view - experimental
• Aim: observe how the
gap influences closure
and collapse
• using full-size screens in
simulated boreholes in
weak rock.
• Sample is 600 mm OD,
215 mm ID, 1000 mm
long. NB: no fluid flow
through rock pores.
Kerosene
Pressure
Camera
Rock
Screen
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Summary of conditions for the screen closure experiments.
Experiment Screen type Gap Conditions
1 Open hole
2 Basepipe Close fit
3 Basepipe + sand filter 3 mm (0.125 in) gap
4 Full screen type 1 Close fit
5 Basepipe Zero gap, small outward stress
8 Basepipe 12 mm (0.5 in) gap
9 Full screen type 2 Close fit
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Example: Test 4. Full screen, close fit
Pressure in bars(500 bars = 7250 psi)
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Closure data from all the experiments
No. Conditions
1 Open hole
2 Basepipe, close fit
3 Basepipe + filter, 0.125 in gap
4 Full screen type 1, close fit
5 Basepipe, small outward stress
8 Basepipe, 0.5 in gap
9 Full screen type 2, close fit
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Transverse view - modelling
• Simple rock deformation model, incorporating support stress (isotropic stress, perfect plasticity, no pore pressure gradients).
• Couples deformation of rock to that of screen.
• Allows study of effects of stiffness, gap, rock properties….
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Typical results from modelling
Result:Optimum gap for mechanical stability: zero to few mm
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Axial view - modelling
• Accounts for – radial flow from formation into well
– axial flow along gap
– radial flow through screen wall
– axial flow in basepipe.
• Tracks movement of sand (if annulus velocity is above threshold value).
• Allows blockage of screen or annulus.
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Effect of gap size:hole ID 0.2 m, screen OD 0.195 m.
Toe Heel
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Effect of gap size:hole ID 0.2 m, screen OD 0.185 m.
Toe Heel
SPE 86463. The Role of the Annular Gap in Expandable Sand Screen Completions.
Conclusions• Most stable system when movement of both grains and
larger fragments is prevented.
• Small gap (few mm) allows mobilization of rock strength to assist stability.
• Sand movement in annulus prevented by smaller gap, because of lower annulus velocity.
• Sand accumulations, plugged screen sections, and enlarged holes lead to local hotspots and potential erosion.
Very small or zero gap is therefore best for long-term integrity of completion.