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

1. 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

2. 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

3. 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)

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

5. What is Soft Sand? (Definition) • Screening criteria (Tony Settari): • Low unconfined compressive stress (UCS) • Low Young’s 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)

6. 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

7. 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)

8. 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

9. Injection well BHFP Injection well: Pressure charging Reservoir pressure Production well: Pressure drawdown Production well BHFP r r 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

10. 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

11. 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

12. 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

13. 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?

14. 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

15. 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?

16. 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)

17. 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