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