There is also a screenless method of frac packing that involves oriented perforating, injecting resin to stabilize the formation and using resin-coated proppants and fi ber technol- ogy to prevent proppant flowback (see “ Going Screenless in Japan,” page 21). This technique joins a growing list of screenless options when operators choose to prevent failure rather than to exclude sand production. In moderately weak but consolidated zones, screenless-completion techniques offer effective solutions to reduce or eliminate sanding, often at lower cost and risk and with increased hydro- carbon production.24
As an important part
of sand management, screenless techniques draw from a range of individual or combined technologies such as selective, dynamically underbalanced, optimally phased and oriented perforating techniques, TSO fracturing designs and indirect vertical fracturing (IVF) techniques, proppant-flowback control, and resin injection for formation consolidation. Extensive research and fi eld experience have demonstrated the importance of perforation orientation to perforation stability and sand pro- duction. When hydraulic fracturing is planned to help prevent sand production, perforations should be aligned with the preferred fracture plane (PFP), or parallel with the maximum in- situ stress direction.25
Orienting perforations
along the maximum in-situ stress direction reduces tortuosity, or the restrictions on near-
20. Venkitaraman A, Behrmann LA and Chow CV:
“ Perforating Requirements for Sand Control,” paper SPE 65187, presented at the SPE European Petroleum Conference, Paris, France, October 24– 25, 2000.
21. Bakker E, Veeken K, Behrmann L, Milton P, Stirton G, Salsman A, Walton I, Stutz L and Underdown D:
“ The New Dynamics of Underbalanced Perforating,” Oil eld Rev iew 15, no. 4 (Winter 2003/2004): 54– 67.
Stenhaug M, Erichsen L, Doornbosch FHC and Parrott RA: “ A Step Change in Perforating Technology Improves Productivity of Horizontal Wells in the North Sea,” paper SPE 84910, presented at the SPE International Oil Recovery Conference in Asia Paci c, Kuala Lumpur, Malaysia, October 20– 21, 2003.
22. Ali et al, reference 19.
23. Ali S, Norman D, Wagner D, Ayoub J, Desroches J, Morales H, Price P, Shepherd D, Toffanin E, Troncoso J and White S: “ Combined Stimulation and Sand Control,” Oil eld Rev iew 14, no. 2 (Summer 2002): 30– 47.
24. Acock et al, Riddles et al, and Pitoni et al, reference 11.
25. Behrmann L, Brooks JE, Farrant S, Fayard A, Venkitaraman A, Brown A, Michel C, Noordermeer A, Smith P and Underdown D: “ Perforating Practices That Optimize Productivity,” Oil eld Rev iew 12, no. 1 (Spring 2000): 52– 74.
Almaguer et al, reference 13. 26. Sulbaran AL, Carbonell RS and Ló pez-de-Cá rdenas JE:
“ Oriented Perforating for Sand Prevention,” paper SPE 57954, presented at the SPE European Formation Damage Conference, The Hague, The Netherlands, May 31– June 1, 1999.
U K
0 0
km 200 miles 200
> Location of Mirren eld (bottom). Complex stresses surround a salt diapir in Mirren eld and must be considered in both drilling and completion operations (top). 3D modeling predicts that the maximum stress orientation near the diapir is tilted 20° to 40° from horizontal, making perforated completion design more complex.
3,000 Stress contrast 4,000 0 1,000 2,000 Norway
Mirren field
3,000 Offset, m
0 to 1 MPa 1 to 2 MPa 2 to 5 MPa 5 to 10 MPa 10 to 20 MPa 20 to 30 MPa 30 to 40 MPa
>40 MPa Surfaces 4,000
5,000 6,000 2,000
wellbore fl ow during hydraulic fracturing. Today, unsurpassed accuracy, repeatability and verifi ca- tion are available with the OrientXact tubing-conveyed oriented perforating system (see “ Perforations on Target,” page 28). However, for wells with perforated-only com- pletions in weak reservoirs, alignment with the PFP will not necessarily result in the most stable perforation tunnels and may instead lead to increased sand production. With a 3D sand-prediction model, the state of stress— the magnitude and direction of the three principal stresses— around the wellbore is modeled, allowing completion experts to select the perfo- ration orientations that minimize stress contrast and maximize perforation stability (previous page, bottom).26
New oriented perforating tech-
nologies have allowed the industry to exploit an increased understanding of the relationship between near-wellbore stresses and sand pro- duction. This technique has now been applied worldwide and its use continues to grow.
0
Oriented Perforating Success in the North Sea Stress contrasts, or high deviatoric stresses, are the source of many borehole-stability and sand- production problems and can be made more severe by local geologic features such as salt diapirs. Given the complex state of stress in the strata adjacent
to a salt diapir, BP was
concerned about the potential for sand produc- tion to jeopardize well productivity and integrity, and production facilities at Mirren fi eld, east of Scotland in the North Sea. Moreover, as the wells produce, depletion causes the effective stress in the reservoir to increase, raising the potential for sand production. With only two sub- sea horizontal producing wells planned for fi eld development, BP needed to select a completion method that would avoid potential
sand
production and minimize future intervention requirements. To simulate the principal stress conditions in the presence of a salt diapir, BP constructed a comprehensive MEM for the Mirren fi eld (below).
1,000 Salt
Spring 2004
19
N o r t h S e a
Depth, m
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