The Perfect
Stimulation Solution™
CASE STUDY
4. Dissolvine® StimWell™
Field Proven Stimulation Technology
A vertical gas well in a deep, sour carbonate reservoir was
successfully stimulated using Dissolvine® StimWell™. Previous
matrix stimulation treatments with conventional acids in this
high temperature gas well did not sustain the performance
and fracturing of the well was considered. However, this case
clearly proves that matrix acidizing with Dissolvine® StimWell™
was the best choice in terms of gas production, well integrity,
and environmental impact.
18
Introduction
The productivity of the well decreased after a
recent work over procedure. Repeated attempts
with various conventional matrix treatments
did not result in persistence of performance.
The well was completed with chrome-nickel
based corrosion resistance alloys. Selection of
stimulation fluid proved challenging because
of the high temperature – greater than 300 °F,
corrosive gases – H2S and CO2, and the presence
of high chrome-nickel alloys, along with low
carbon steel content tubular.
Design
To address the difficulties posed by the tough
field conditions, a careful set of laboratory
studies was conducted at bottom-hole
­conditions, including: corrosion tests for
­different metallurgies present in the well,
compatibility with various production fluids
and core-flood tests.
Core-flood tests helped determine the optimum
treatment volume and concentration. To protect
the down-hole equipment under the heavy H2S
and CO2 conditions, corrosion tests were an
integral part of the treatment preparation.
With a minimal amount of corrosion inhibitor the
corrosion rate was kept well below the required
0.05 lbs/ft2 limit. In addition to the superior
corrosion performance, Dissolvine® StimWell
passed all required compatibility tests with other
production related chemicals.
Treatment program
A customized matrix program was designed
to cope with the challenging reservoir condition
and the strict environmental legislation of the
region. The treatment included a pre-flush,
main-flush and a post-flush. The objective of
the pre and post flushes was to prevent water
blockage and to improve the flow back
­performance. The main fluid contained
­Dissolvine® StimWell, with minimum
­concentration (less than1%) of a corrosion
inhibitor for added protection at the elevated
temperature and against the corrosive gases.
The treatment was applied by bull-heading.
The flush back and production was started after
certain soaking time.
Production Rate (% of original rate)
250
+110%
200
150
Figure 11: Measured gas
production before and
after treatment with
Dissolvine® StimWell.
For comparison the
expected acidizing and
fracturing treatment
results are given.
100
50
0
pretreatment
post
treatment
target
expected
fracturing
result
19
Results
The treatment with Dissolvine® StimWell
resulted in significant increase in gas
production. After the treatment the gas
production of the well improved by 110 percent
of the initial production. The treatment efficiency
with Dissolvine® StimWell was excellent, as the
result exceeded not only the target set for the
acidizing job, but the resulting production rate
nearly equaled the result expected if the well
was fractured. Extensive analysis of the flow
back samples after treatment indicated that
Dissolvine® StimWell dissolved large amounts of
calcite and dolomite without any adverse impact
on the well tubular.
Based on the narrow gap between the improved
production rate achieved and the expected result
of fracking the well, Dissolvine® StimWell can be
a real alternative to fracturing systems,
especially considering the economic,
environmental and regulatory aspects.
Environment and safety
Due to its environmentally-friendly nature and
non-hazardous properties Dissolvine® StimWell
easily met all the strict regulations and
environmental guidelines set by the regulatory
bodies and by the operator. Dissolvine® StimWell
proved easy to handle in the field, leading to
much safer working conditions, especially in
comparison with conventional acid treatments.
Less logistics were also needed as only two
components were in use for the main treatment
and a much smaller volume was pumped when
compared with conventional acids.
Overall this case study convincingly proves that
Dissolvine® StimWell is The Perfect Stimulation
Solution™
• combining numerous advantages
• removing formation damage
• improving production rate
• maintaining well integrity.
Dissolvine® StimWell™
The Perfect Stimulation Solution™
Improving the production of an oil well by stimulation with
strong acids such as HCl is a well-established and effective
technique. However, due to the increasingly difficult and high
temperature conditions, the application of these acids may
create more problems than it actually solves.
We have found a solution for these challenging conditions.
AkzoNobel has developed a stimulation fluid based on the
chelating agent GLDA which can be used under tough conditions
in carbonate and sandstone formations. Dissolvine® StimWell
combines all the advantages of current stimulation fluids ­without
the disadvantages.
Dissolvine® StimWell:
Effective for carbonate and sandstone
Applicable over a wide temperature range (up to 400°F)
No or very low corrosion
Requires minimum additives
C
auses no formation damage
• no face dissolution
• prevents iron precipitation
• prevents sludge formation
• compatible with clays
Biodegradable
Safe and easy to handle
Cost effective