Summary
Matrix acidizing is used in carbonate formations to create flow channels
from the formation to the wellbore; in sandstone formations, however, the goal
is to dissolve materials that impair well performance. However, the use of
acids in deep wells has some major drawbacks, including high reaction rate and
corrosion to well tubulars.
We have discovered a new stimulation chemical that can be used as a
replacement for or in combination with acid treatments in deep wells. A
polyacid whose structure allows for acidification is described. The polyacidic
chelate L-glutamic acid, N, N-diacetic acid (GLDA) is manufactured from
L-glutamic acid (MSG). The chelate-based fluid very effectively dissolves
CaCO3, and it is less corrosive to the equipment and easy to
handle.
This paper discusses the reaction of the new chelate, GLDA, with calcite and
compares its performance with other available chelates, including
ethylenediaminetetraacetic acid (EDTA), hydroxyethylethylenediaminetriacetic
acid (HEDTA), nitrilotriacetic acid (NTA), and ethanoldiglycine (EDG). GLDA
dissolves calcite over a wide pH interval, although it is less effective than
HEDTA at pH > 5. A unique property of GLDA is its high solubility;
solutions exceeding 40 wt% can be achieved at a pH of approximately 2, whereas
HEDTA solubility is limited to approximately 10 wt%. A mole of GLDA with a
natural pH of approximately 1.5 is capable of dissolving up to two moles of
CaCO3. Throughout the pH range, GLDA appears to be as thermally
stable as HEDTA.
As an additive to hydrochloric acid (HCl), GLDA is as effective as HEDTA in
preventing precipitation of moderate levels of Fe3+ in spent acids.
At high Fe3+ concentrations, GLDA is slightly less effective than
HEDTA on a molar basis; but, to deal with high Fe3+ levels, GLDA may
be better because significantly higher concentrations of it are possible in
various acids. In 28 wt% HCl, HEDTA has limited solubility while GLDA's
solubility exceeds 40 wt%.
From an environmental standpoint, GLDA is readily biodegradable and is made
from a renewable raw material, monosodium glutamate. GLDA has low toxicity and
aquatic toxicity characteristics. As a replacement for HCl, GLDA is
significantly safer and less corrosive.
© 2010. Society of Petroleum Engineers
View full textPDF
(
438 KB
)
History
- Original manuscript received:
24 February 2009
- Meeting paper published:
21 April 2009
- Revised manuscript received:
2 March 2010
- Manuscript approved:
9 March 2010
- Published online:
19 August 2010
- Version of record:
15 March 2011
View Cart
