A Preliminary Review of Completion Practices in Soft (Unconsolidated) Sandstone Formations- Public Domain and JIP Information
Bjarni Palsson, Stavros Kastrinakis
Preliminary Review:- Soft Sand Completion Practices
General Items for Discussion
General Completion Options for Water Injectors
Completion Guidelines for Water InjectorsMorita et al., paper SPE 39436
Objective: Best Practices Document
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)
Soft Sand Completion Issues
What is a Soft Sand (Definition)
Formation Failure Mechanism
Completion Design Criteria
Completion Field Experience
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 testsSand production and wellbore stability problemsStress dependent porosity and permeability
Stress Path (Heriot-Watt)
Completion Failure in Soft Sand Wells
Perforation cavity or wellbore collapse
Hardware damageErosion and corrosion (during installation and
operation)
Compaction (well collapse)
Screen pluggingSand production
Oil and solids in injection water
Formation Failure in Soft Sand Wells
Perforation 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)
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
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
r
Reservoir pressureReservoir pressure
Injection well BHFPInjection well BHFP
Injection well:Pressure charging
Injection well:Pressure charging
Production well:Pressure drawdown
Production well:Pressure drawdown
Production well BHFPProduction well BHFP
r
Field Experience
Public Domain Literature
PWRI JIP InformationBP Amoco: BP-1, BP-2, BP-3, BP-4, BP-5Norsk Hydro: NH-1PanCanadian Petroleum: Countess fieldStatoil: Heidrun field, Snorre field
Unconsolidated - not necessarily soft sand!Either fulfill “screening criteria” or(Very) high permeability
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 actionsSand control
Eliminate water hammer effects
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
Performance of Pre-Packed Screens
Successful applicationsBP 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 controlBut still sand production - Gravel size too
high?
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 controlProduction wells had no sand production
problemsBut sand production in some of the injectors
Sun Oil Britain: Balmoral FieldSimilar formation as Forties ??Both producers and injectors (successfully)
gravel packed
Issues for Discussion
Water Hammer Effects (WHE)How and when do water hammer effects occur?
Retainer valvesCan installation of retainer valves above perforations
stop water hammer effects?
Injectors versus producersWhy Forties injectors have more sand production
problems than the producers?
Corrosion and erosion problemsNeed for corrosion protection in injection well
completions and risk of debris plugging?
Issues for Discussion
Innovative solutionsMechanical 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)
Issues for Discussion
Measurements of completion efficiencyQ, THP, II or SkinPermeability-adjusted skin
Pahmiyer et al. (SPE 54742):
Trend line relationship between permeability and skin
0
5
10
15
20
25
30
35
40
0 500 1000 1500 2000 2500 3000
Permeability (md)
Skin factor
Frac-pack trendline
HRWP