incrustração

An Environmentally Friendly Stimulation Fluid for
High Temperature Applications
J.N. LePage, C.A. De Wolf and J.H. Bemelaar – AkzoNobel
H.A. Nasr-El-Din – Texas A&M University

SPE 121709

Overview
Strong and weak acids in stimulation
Use of chelates in stimulation
GLDA chelate and properties
GLDA performance in stimulation fluids:
- iron control
- calcite dissolution
- thermal stabilty
Conclusions

Stimulation with Strong Acids
2 HCl + CaCO3 → Ca2+ + 2 Cl- + CO2 + H2O
‘Protonation reaction mechanism’
Advantages of HCl:
1 gallon of 15 % HCl dissolves ~ 1.8 lbs CaCO3
Readily available - cheap
Lots of experience
Highly effective

Stimulation with Strong Acids
2 HCl + CaCO3 → Ca2+ + 2 Cl- + CO2 + H2O
Disadvantages of HCl:
Reaction may be too fast / uncontrolled
Corrosion of tubulars
Temporary migration of Fe3+ → Fe(OH)3
Problems are aggravated at high temperatures.

Stimulation with Weak Acids
2 HAn + CaCO3

Ca2+ + nA- + CO2 + H2O

Advantages (acetic, formic, citric)
Slower / controlled reaction
Reduced corrosion
Some Fe3+ control (citric)
Disadvantage:
Greatly reduced CaCO3 dissolving power
(higher molecular weight and ~ 10 wt % solutions)

Alternatives – Chelates
Chelates are chemical agents that interact (complex) with metal ions, thus changing the chemical property of the metal ion.
Virtually all multi charged metal ions like Ca2+ and Fe3+ can be chelated.
Usually allows for greater solubility of the metal ion.
The chelate-metal ion bond is reversible.

Chelates Used in Stimulation
COOH
HOOC

N

N

COOH

HOOC

COOH
HO
HOOC

EDTA

HOOC

COOH

N

N

N

HEDTA

COOH

HO

N

COOH

NTA

COOH
COOH

EDG
(HEIDA)

Stimulation with Chelates
Chelates are used with acids to prevent Fe3+ precipitation:
EDTA4- + Fe3+

[EDTA-Fe]1-

But chelates can also dissolve calcite:
EDTA4- + CaCO3

[EDTA-Ca]2- + CO32-

Stimulation with Chelates
EDTA4- + CaCO3