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Quartz School for Well Fluids Site Supervisors 9. Completion Module – 12 Well Completions Schlumberger Private

Section – 9 Completions Fluids

Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Content Functions and Properties Design of Completion Fluid Types and Applications Testing

Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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• • • •

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9. Completion Fluids

Functions & properties Definition Schlumberger Private

• A clear, solids free fluid that is displaced into the hole prior to running the completion. • The density of the fluid is achieved by dissolving soluble salts in the water. • Eg: NaCl, KCl, CaCl2, CaBr, NaBr, ZnBr or formate salts – potassium, caesium

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9. Completion Fluids

Content Functions and Properties Design Formulation and Composition Testing

Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

Schlumberger Private

• • • •

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9. Completion Fluids

Functions & properties Applications Schlumberger Private

A completion fluid can be used for:

• Conditioning the well prior its activation • Conducting completion operations • Performing work over operations & well intervention • Temporal or definitive well abandonment

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9. Completion Fluids

Functions & properties General Procedure: Schlumberger Private

• Displace the drilling fluid with a clean fluid (like filtered brine) • Perform well clean up after work over operations • Completion brines are frequently used as perforating or gravel pack fluids

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9. Completion Fluids

Functions & properties Drilling fluid displacement Schlumberger Private

The reasons the drilling fluid must be displaced are: • To have a clean fluid (solids free) inside the casing in front of the intervals to perforate •

A viscous spacer is regularly pumped ahead the completion fluid to avoid its contamination and improve the displacement

•

Polymers and surfactants are commonly added to the spacers

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9. Completion Fluids

Functions & properties Displacement and spacers Mud Schlumberger Private

Chemical wash: - Cleaning wellbore Completion Fluid Spacer: Separation

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9. Completion Fluids

Content Functions and Properties Design Formulation and Composition Testing

Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

Schlumberger Private

• • • •

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9. Completion Fluids

Design Basis of Design Schlumberger Private

• The design of these fluids will depend on reservoirs and production techniques, • The constraints in formulating the fluid : • Rock character, • Pore size distribution, • Pore pressure, • Hydrostatic pressure, • Temperature. Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Design Options for Fluid Design:

•

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• Completion fluids may be formulated as foams, brines, crude / refined oil, pneumatic fluids or emulsions, Low and high density completions brines are available on the market.

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9. Completion Fluids

Design Completion fluid design

Density

Crystallization

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Completion Fluid Compatibility

Filtration

Corrosion Rheology

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9. Completion Fluids

Design Density requirement Schlumberger Private

• The primary performance requirement for a completion fluid is hydrostatic pressure control, • The density must be sufficient to produce a hydrostatic pressure in the wellbore to control formation pressures, • An over balance of 200 of 300 psi above bottom hole reservoir pressure is generally used for well control. • An exception can be when a well is displaced to underbalanced completion fluid with a cemented and tested liner and with BOPs on. After installing the tree, it can be perforated under balance in a controlled environment. Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Design Density requirement

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• Temperature and pressure corrections are generally needed for deep wells to control pressure and avoid excessive overbalance pressures • The brine density decreases with increasing temperatures because of thermal expansion • Density increases with increasing pressure because of compressibility • The temperature effects dominate the pressure effects as the depth of the well increases

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9. Completion Fluids

Design • Density and Temperature correction ; • The brine density to be mixed at surface at Schlumberger Private

• 70 °F will be related to the density required at bottom hole temperature with Schmidt equation :

Density ( 70 F = Density + ( T avg - 70 ) * E f Ef : expansibility factor T avg = average well Temperature T avg = ( Surface Temp + bottom hole Temp) / 2

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9. Completion Fluids

Design Crystallization requirement Schlumberger Private

• The crystallization temperature is the second most important selection criterion for a completion brine, • The crystallization temperature is the temperature at which the least-soluble salt becomes insoluble and precipitates out.

• The crystallization point is the equilibrium temperature when the crystals form

• The crystals can be either solids or freshwater ice. Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Design Crystallization • FCTA - TCT - LCTD Schlumberger Private

°F

ZnBr 2 / CaBr 2 curve ( 19.2 ppg )

40 Crystal Dissolve

30 Crystallization Temperature

20 First Crystal 10

Cooling 10

Heating 20

30

40

50

60

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9. Completion Fluids

Design Crystallization

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• Crystals and precipitation can lead to a number of problems

• The density may be reduced • The crystallized salts settle in the pits, • Brine viscosity increases with salt crystals, brine appears to be frozen solid, • Lines are plugged, • Ice plugs form in the riser or the wellhead or the BOP stack • Lost rig time and significant expense • The process requires a significant amount of energy (heat) to reverse the effects. Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Design Formation compatibility requirements Schlumberger Private

• The third selection criterion is the completion brine will be chemically compatible with the formation rock, water and hydrocarbons • Incompatibilities cause formation damage, blocking pore openings and pore-throat plugging.

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9. Completion Fluids

Design Compatibility with formation clays Schlumberger Private

• The main concern is with formation clay compatibility • The contact with reservoir rock will cause swelling and / or deflocculating of formation clay To prevent clay swelling a completion fluid must meet a minimum salinity requirement. ( 3% NH4Cl or 2 % KCl )

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9. Completion Fluids

Design Compatibility with formation waters Schlumberger Private

• Incompatibility with formation water can lead to the formation of scales • Scales are the result of the deposition of inorganic material • The scales found in formation water are Calcium, Iron carbonates, sulfates and silicate, • Scales can be formed by mixing incompatible waters Example is formation water containing Barium and seawater with sulfates leading to Barium Sulfate deposition

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9. Completion Fluids

Design Compatibility with formation fluids

• The incorporation of surfactants or solvents will be necessary • Natural gas as such CO2 could cause calcium carbonate precipitation if a calcium based brine (CaCl2) is selected • Compatibility with completion equipment seals This is important for ‘‘packer fluid’’ (fluid left between tubing hanger and packer). PH plays a part here as well. Example: amine base inhibitors are not compatible with Viton seals Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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• The main concern is the formation of oil-water emulsion and / or sludge which will block pores and cause formation damage

9. Completion Fluids

Content Functions and Properties Design Formulation and Composition Testing

Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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• • • •

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9. Completion Fluids

Formulation & Composition Completion fluids Schlumberger Private

• Low density fluids • Foams • Emulsions • High density fluids, • Brines

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9. Completion Fluids

Formulation & Composition High density Brines:

POTASSIUM SODIUM MAGNESIUM CALCIUM SODIUM CALCIUM ZINC

( 8.3 ppg)

Schlumberger Private

Brines : 1.00sg

- 2.3sg ( 19.0 ppg )

Chloride -( K Cl ) d : 1.16 ( 9.6 ppg ) Chloride- ( NaCl ) d : 1.20 ( 9.9 ppg ) Chloride- ( Mg Cl 2 ) d : 1.30 (10.8 ppg ) Chloride- ( Ca Cl 2 ) d : 1.40 (11.6 ppg ) Bromide- ( Na Br2 ) d : 1.51 (12.5 ppg ) Bromide- ( Ca Br 2 ) d : 1.80 (14.9 ppg ) Bromide- ( Zn Br 2 ) d : 2.30 (19.0 ppg )

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9. Completion Fluids

Formulation & Composition High density Brines

Brine mixtures* : 1. 00 ( 8.3 ppg)Economical formulations d = 1.20 - 1.40 - NaCl + CaCl2 - NaCl + Na2CO3 d = 1.20 - 1.27 - NaCl + NaBr d = 1.20 - 1.51 - CaCl2 + CaBr2 d = 1.40 - 1.80 - CaBr2+ ZnBr2 d = 1.80 - 2.30

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2.3 ( 19.0 ppg )

( 9.9 - 11.6 ppg ) ( 9.9 - 10.5 ppg ) ( 9.9 - 12.5 ppg ) (11.6 - 14.9 ppg ) (14.9 - 19 ppg )

* Crystallization points / Tables Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Formulation & Composition High density Brine POLYBRINE system : Schlumberger Private

Formulation of polymers and carbonates used as a viscosifier and seepage loss control agent in completion brines. Prevent excessive filtrate invasion Formation protection from solids block Acid soluble

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9. Completion Fluids

Formulation & Composition Products Schlumberger Private

• Others acid soluble products used • XC Polymer if suspension is required, • Blends of polymers, calcium lignosulfonate and NaCl particulate, • Used as bridging, viscosifier and suspension agent • The sealing ability may be enhanced with the addition of supplemental bridging agent

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9. Completion Fluids

Content Functions and Properties Design Formulation and Composition Testing

Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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• • • •

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9. Completion Fluids

Testing Testing issues Schlumberger Private

• The fluid properties need to be tested in the field. • Tests conducted on : • Filtration, • Rheology, • Fluid loss control, • Weighting, • Crystallization temperature • Corrosion. Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Testing Filtration Schlumberger Private

• The fluid that contacts the formation must IDEALLY be particle – free • particularly in the case of overbalanced perforating • Even in under balance perforating, solids content affects perforation crush zone permeability • Sources of particles inside fluids: • Solids from mud incorporated during displacement, • Scales in pits and storage, • Insoluble impurities in salts or other components, • Solids and fines in suspension with waters.. Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Testing Filtration process Schlumberger Private

• Mixing plant filtration use two stages process : • Fluid is passed through a 10-micron filter cartridge, • Then fluid is filtered with a 2-micron pleated paper cartridge.

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9. Completion Fluids

Testing Filtration process Schlumberger Private

• The quality control of filtration is the degree of clarity. • Additional measurements will be conducted: • Turbidity, • Particle size distribution, • Gravimetric measurements of total solids.

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9. Completion Fluids

Testing Rheology measurement Schlumberger Private

• Rheology is tested with the rotating viscosimeter Fann, model V-G (Viscosity and Gel measurements), widely used in the drilling- fluid industry, • A rotating - cylinder turning around a bob connected to a torsion spring measures the viscosity in terms of the relationship between the shear stress vs. shear rate • The Brookfield viscometer is used to measure a very low shear rates viscosity to enhance suspension properties of the fluid. Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Testing Fluid loss control

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• The completion fluid must be designed for minimum filtrate invasion in the formation in static and dynamic conditions. • Tests conducted: • Spurt loss, • API test filtration , • High temperature and high pressure static filtration • An alternative is the use of one CaCO3 / polymer ‘pill’ to control fluid loss

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9. Completion Fluids

Testing Weighting Schlumberger Private

• The density of a completion fluid will need adjustments. • Weighting up (increasing density) with solids salts or heavy brine • Weighting down (decreasing density) will be done by dilution with fresh water or a lower-density brine, • Testing with mud balances or hygrometer.

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9. Completion Fluids

Testing Corrosion Schlumberger Private

• Electrical conductivity of fluid (brine ) permits corrosion of metals • Corrosion rate is important if the fluid has a low pH or contains dissolved oxygen, • The solubility of oxygen decreases in brines as salt saturation is approached • Injection of oxygen scavenger (eg ammonium bisulfite) may be needed • Filming -amine type - brine soluble corrosion inhibitors are frequently used in completion brines • Thioconate chemicals as corrosion inhibitors will form a film on the surface of steel or iron in zinc based brine environment. Quartz School. Module 12: Well Completions / Section 9: Completions Fluids

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9. Completion Fluids

Conclusion

• • • •

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• Working with completion fluids, aspects to be considered are: • Rig equipment and precautions • Field mixing procedures Displacement procedures Typical properties of the fluids Calculations and formulations tables Health and Safety implications of mixing and handling various brines

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