Acid Fluid Design

8/22/2019 Acid Fluid Design

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BJ Services

Acidizing Treatment

Fluid Design
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Acidizing Treatment Fluid Design

The Main Problems:-

1. Corrosion of Tubulars

2. Iron Precipitation

3. Changes in Relative Permeability4. Emulsions

5. Sludges

6. Formation Water Incompatibility7. Fines

8. Asphaltenes and Paraffins

9. Problem Formations


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The Problem:-

Corrosion of steel tubulars by HCl,

HF and organic acids whilst they

are downhole.


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The Solution:-Use Corrosion Inhibitors and Inhibitor

Intensifiers in the acid. Inhibitors

greatly reduce corrosion rate.


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Corrosion Inhibitors

We Need to Know:-

TemperatureAcid Blend (strength and type)

Job Type (coil tubing?)

Completion Type (N80, Chrome etc)H2S?

Other Additives in Acid


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Corrosion Inhibitors

Inhibitors:

CI-25, CI-27 General PurposeCI-30 High Temperature

Intensifiers:

Hy-Temp OHy-Temp I

Hy-Temp 400


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2. Iron Precipitation

The Problem:-

The precipitation of Iron Hydroxidesand Iron Sulphide.

The Solution:-

Iron Reducing Agents, Iron Chelating

Agents and pH Control Additives.


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Iron Precipitation

We Need to Know:-


H2S?

Other Additives in AcidCondition of Tubulars

Iron Compounds in Formation


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Iron Precipitation

FeCl3 causes precipitates if pH > 2.5

FeCl2 causes precipitates if pH > 4.5

and if H2S is present

FeS precipitates if pH > 1.9


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Iron Precipitation

So, Either Keep the pH < 1.9

orReduce the Fe(III) to Fe(II) and

Keep the pH < 4.5

orChelate the Iron into Soluble

Complexes


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Iron Precipitation

pH Control Additives:

SAPP, Acetic Acid

Reducing Agents:

Ferrotrol-200, -210

Chelating Agents:

Ferrotrol-300, -800, -810, -900, -1000


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3. Changes in Relative Permeability

The Problem:-

Changes in the wettability of the

formation.

The Solution:-Use of surfactants.


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We Need to Know:-



Formation MineralogyFormation Fluids

Changes in Relative Permeability


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Changes in Relative Permeability

BJs products help keep the formation

water wet, and reduce surface tension.

Flo-Back 20, 30Inflo-100, -150


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4. Emulsions

The Problem:-

Formation of thick, pore blockingemulsions by interaction of formation

and acid.

The Solution:-

Use of surfactants.


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We Need to Know:-

Temperature

Acid Blend (strength and type)


Formation Fluids

We Also Need:-

Samples of All Formation Fluids

Emulsions


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Emulsions

BJ Products:-

Inflo-100

NE-2A, -32, 940

BJ Services has a very wide rangeof surfactant products.


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5. Sludges

The Problem:-

Formation of sludges by action ofheavy oils with acid blends, in the

presence of Fe3+ ions.

The Solution:-

Use of anti-sludging agents,

iron reducing agents.


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We Need to Know:-

Temperature

Acid Blend (strength and type)Other Additives in Acid

Formation Fluids

We Also Need:-

Samples of All Formation Fluids

Sludges


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Sludges

Anti-Sludging Agents:-

NE-13, -32AS-3, -7

Iron Reducing Agents:-Ferrotrol-200, -210


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6. Formation Water Incompatibility

The Problem:-

Formation of precipitates due tobrines and acid incompatibility

The Solution:-Testing of formation water


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Formation Water Incompatibility

We Need to Know:-



We Also Need:-

Sample of Formation Water


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7. Fines

The Problem:-

Formation of fine insoluble particles

The Solution:-

Accurate knowledge of formationmineralogy, fines suspending agents.


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Fines

We Need to Know:-



Formation Mineralogy


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Fines

Fines Suspending Agents:-

LT-21

NE-38


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8. Asphaltenes and Paraffins

The Problem:-

Asphaltene and paraffin depositsfrom oil production

The Solution:-Solvent-acid blend


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Asphaltenes and Paraffins

We Need to Know:-



We Also Need:-

Sample of Deposits


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Asphaltenes and Paraffins

Acid System:-

One Shot Acid Plus


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1. Carbonate w ith High Quartz Con tent.

Acidizing this formation can lead

to the production of sand and fines.


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2. Carbonate w ith High Iron content.

Increased tendency to produce iron

hydroxide precipitates - acid will

neutralise almost completely, giving

a high pH.


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Problem Formations

3. Soft Carbonate Format ions.

These formations will tend to deform

after acid treatment, closing up

wormholes and other areas of rock

removal.


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Problem Formations

4. Sandstones w i th High Carbonate

Content.

These formations will produce

significant amounts of CaF2 solids

when stimulated with HCl:HF.


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Problem Formations

5. Sandstones w ith High Clay Con tent.

Reduced penetration of live HCl:HF.

Increased tendency to produce

precipitates.


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Problem Formations

6. Weak o r Unconsol idated Sandstones

Acidizing these formations will

lead to the production of sand.


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Core Flow Testing

Core Flow Testing is THE BEST WAY

to ensure compatibility between the

formation and the stimulation fluids.

It can also be used to optimise thetreatment and fluid design.


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Summary

Most of the problems with acidizing can

be countered if we know:-

1. Temperature

2. Formation Fluids

3. Formation Mineralogy4. Completion

Documents

Acid Fluid Design