A%20Preliminary%20Review%20of%20Completion%20Practices%20in%20Soft%20(Unconsolidated)%20Sandstone%20Formations

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Preliminary Review- Soft Sand Completion
Practices

• A Preliminary Review of Completion Practices in
  Soft (Unconsolidated) Sandstone Formations
• - Public Domain and JIP Information
• Bjarni Palsson, Stavros Kastrinakis

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General Items for Discussion

• General Completion Options for Water Injectors
• Completion Guidelines for Water Injectors
• Morita et al., paper SPE 39436
• Objective Best Practices Document

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Completion Methods for Water Injection Wells
(General)

• Gravel / frac-packing
• Open hole with a screen or a pre-packed screen
• Cemented perforated casing/liner with a propped
  hydraulic or thermally induced fracture
• Selective perforation
• Open hole (barefoot)

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Soft Sand Completion Issues

• What is a Soft Sand (Definition)
• Formation Failure Mechanism
• Completion Design Criteria
• Completion Field Experience

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What is Soft Sand? (Definition)

• Screening criteria (Tony Settari)
• Low unconfined compressive stress (UCS)
• Low Youngs modulus (E)
• Poro-plastic compressive behaviour (low cohesion)
• Poor core integrity and wash-out during lab tests
• Sand production and wellbore stability problems
• Stress dependent porosity and permeability
• Stress Path (Heriot-Watt)

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Completion Failure in Soft Sand Wells

• Perforation cavity or wellbore collapse
• Hardware damage
• Erosion and corrosion (during installation and
  operation)
• Compaction (well collapse)
• Screen plugging
• Sand production
• Oil and solids in injection water

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Formation Failure in Soft Sand WellsPerforation
Cavity Collapse

• Caused by
• Rock mechanical failure (changes in total stress
  and differential stress)
• Chemical unstability (cementation, capillary
  pressure)
• Due to
• Backflow as a stimulation treatment
• Crossflow during well shut-in (layered sands)
• Pressure disturbance as a result of well shut-in
  (water hammer effect)

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Formation Failure in Soft Sand Wells

• Results in injectivity decline due to sand filled
  perforations
• Morita et al. (SPE 39436) In high permeable
  sand, permeability of sand filled perforations
  can be much lower than the initial permeability
• Up to 70 of the injection pressure drop (Pwf-Pe)
  occurs within the sand filled perforations
• Sand filled perforations may be more prone to
  plug by solids in the injection water

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Design Criteria for Injection Well Completion

• In general, same rules as for production wells
• Difference
• Near wellbore area of injection wells is pressure
  charged
• Injection wells have to withstand solids flow in
  two directions

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Field Experience

• Public Domain Literature
• PWRI JIP Information
• BP Amoco BP-1, BP-2, BP-3, BP-4, BP-5
• Norsk Hydro NH-1
• PanCanadian Petroleum Countess field
• Statoil Heidrun field, Snorre field
• Unconsolidated - not necessarily soft sand!
• Either fulfill screening criteria or
• (Very) high permeability

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Formation Failure after well Shut-in(Water
Hammer Effect)

• Statoil Heidrun Field (PWRI JIP)
• Highly unconsolidated formation
• Injection wells completed without sand control
• Sharp injectivity decline linked to emergency
  shut-ins
• Liquefied sand believed to fill the wellbore
  above perforations
• Possible remedial actions
• Sand control
• Eliminate water hammer effects

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Formation Failure after well Shut-in(Water
Hammer Effect)

• Petrobras Marlim Field (SPE 53789)
• Production wells and horizontal injection wells
  completed with sand screens
• Deviated injection wells without sand control
• Sand production associated with shut-ins (WHE)
• Solved with retainer valves above perforations

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Performance of Pre-Packed Screens

• Successful applications
• BP Amoco Harding Field (SPE 48977)
• Petrobras Marlim (SPE 53789)
• BP-3 and BP-4 (PWRI JIP)
• Sun Oil Britain Balmoral field (SPE)
• Wilmington field, California (SPE 1543)
• Pre-packed screens the best sand control
• But still sand production - Gravel size too high?

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Comparison between Production Well and Injection
Well Completion Strategies

• BP Amoco Forties Field (SPE 6677)
• Initially both producers and injectors cemented
  and perforated but no sand control
• Production wells had no sand production problems
• But sand production in some of the injectors
• Sun Oil Britain Balmoral Field
• Similar formation as Forties ??
• Both producers and injectors (successfully)
  gravel packed

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Issues for Discussion

• Water Hammer Effects (WHE)
• How and when do water hammer effects occur?
• Retainer valves
• Can installation of retainer valves above
  perforations stop water hammer effects?
• Injectors versus producers
• Why Forties injectors have more sand production
  problems than the producers?
• Corrosion and erosion problems
• Need for corrosion protection in injection well
  completions and risk of debris plugging?

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Issues for Discussion

• Innovative solutions
• Mechanical profile control with mandrels in water
  injection wells Needham et al. (SPE 54746)
• Single Trip Perforating and Gravel Pack System
  (STPP) Jones (SPE 54285)
• Low cost formation consolidation with steam
  injection in the Wilmington field Davies et al.
  (SPE 38793)
• Guidelines for solving sand problems in water
  injection wells
• Morita et al. (SPE 39436)

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Issues for Discussion

• Measurements of completion efficiency
• Q, THP, II or Skin
• Permeability-adjusted skin
• Pahmiyer et al. (SPE 54742)
• Trend line relationship between permeability and
  skin