Recent laboratory and field studies indicated that polymer-based in situ gelled acids can cause formation damage. Coreflood experiments using single-stage and multistage acids were conducted at 250 °F. 15 wt. % regular HCl and 5 wt. % in situ gelled acid-based on Fe(III) as a crosslinker were the acids that were used in this study. Propagation of acids and crosslinker inside 20 in. long cores was examined for the first time in detail. Stage volume and injection rate, which were the parameters that affect the propagating of various chemical species, were examined. Samples of the core effluent were collected and the concentrations of calcium, crosslinker, and acid were measured. Material balance was conducted to determine the amount of cross-liker that retained in the core. The results show that in situ gelled acid should be pumped at low injection rates. In situ gelled acid at low injection rate instantaneously plugged the tip of the wormhole and did not create additional wormholes inside the core. Therefore, when the final regular acid stage bypassed the gel, it started to propagate from nearly the last point that the first stage ended. In site gelled acid stage volume should not exceed 0.5 PV. No benefits were gained by increasing the volume of in situ gelled acids. Retention of total iron in the core increased in multistage acid treatments, especially at low acid injection rates.

References

References
1.
Kalfayan
,
L. I.
, and
Martin
,
A. N.
, 2009, “
The Art and Practice of Acid Placement and Diversion: History, Present State and Future
,”
SPE Annual Technical Conference and Exhibition
, New Orleans, Louisiana, Oct. 4–7, SPE 124141.
2.
Li
,
J.
,
Crabtree
,
A.
,
Kuchel
,
M.
, and
Diaz
,
J.
, 2008, “
Sand/Well Vacuuming Technology With Concentric Coiled Tubing: Best Practices and Lessons Learned from Over 600 Operations
,”
SPE Asia Pacific Oil and Gas Show and Exhibition
, Perth, Australia, Oct. 20–22, SPE 115303.
3.
Smith
,
C. L.
,
Anderson
,
J. L.
, and
Roberts
,
P. G.
, 1969, “
New Diverting Techniques for Acidizing and Fracturing
,”
SPE California Regional Meeting held in San Francisco
, CA, Nov. 6–7, SPE 2751.
4.
Jin
,
L.
,
Wong
,
P.
, and
Sinanan
,
B.
, 2007, “
Optimizing Diversion and Pumping Rate to Effectively Stimulate Long Horizontal Carbonate Gas Wells
,”
SPE European Formation Conference
, Scheveningen, The Netherlands, 30 May–1 June, SPE 107749.
5.
Deysarkar
,
A. K.
,
Dawson
,
J. C.
,
Sedillo
,
L. P.
, and
Knoll-Davis
,
S.
, 1984, “
Crosslinked Acid Gel
,”
J. Can. Pet. Technol.
,
23
(
1
), pp.
24
26
.
6.
MaGee
,
J.
,
Buijse
,
M. A.
, and
Pongratz
,
R.
, 1997, “
Method for Effective Fluid Diversion When Performing a Matrix Acid Stimulation in Carbonate Formations
,”
SPE Middle East Oil Show
, Bahrain, Mar. 15–18, SPE 37736.
7.
Hill
,
D. G
, 2005, “
Gelled Acid
,” U.S. Patent No. US2005/0065041 A1, Mar. 24.
8.
Yeager
,
V.
and
Shuchart
,
C
, 1997, “
In Situ Gels Improve Formation Acidizing
,”
Oil Gas J.
,
95
, pp.
70
72
.
9.
Metcalf
,
S.
,
Lopez
,
H.
,
Hoff
,
C.
, and
Woo
,
G.
, 2000, “
Gas Production From Low Permeability Carbonates Enhanced Through Usage of a New Acid Polymer System
,”
SPE/CERI Gas Technology Symposium
, Calgary, AB, Canada, Apr. 3–5, SPE 59756.
10.
Saxon
,
A.
,
Chariag
,
B.
, and
Abdel Rahman
,
M. R.
, 2000, “
An Effective Matrix Diversion Technique for Carbonate Reservoirs
,”
SPEDC
,
15
(
1
), pp.
57
62
.
11.
Mohamed
,
S. K.
,
Nasr-El-Din
,
H. A.
, and
Al-Furaidan
,
Y. A.
, 1999, “
Acid Stimulation of Power Water Injectors and Saltwater Disposal Wells in a Carbonate Reservoir in Saudi Arabia: Laboratory Testing and Field Results
,”
SPE Annual Technical Conference and Exhibition
, Houston, Texas, Oct. 3–6, SPE 56533.
12.
Nasr-El-Din
,
H. A.
,
Chesson
,
J. B.
,
Cawiezel
,
K. E.
, and
Devine
,
C. S.
, 2006, “
Field Success in Carbonate Acid Diversion, Utilizing Laboratory Data Generated by Parallel Flow Testing
,”
SPE Annual Technical Conference and Exhibition
, San Antonio, TX, Sept. 24–27, SPE102828
13.
Coulter
,
G. R.
and
Jennings
,
A. R.
, 1999, “
A Contemporary Approach to Matrix Acidizing
,”
SPE Prod. Facil.
,
14
(
2
), pp.
144
149
.
14.
Bazin
,
B.
, 2001, “
From Matrix Acidizing to Acid Fracturing: A Laboratory Evaluation of Acid/Rock Interactions
,”
SPE Prod. Facil.
,
16
(
1
), pp.
22
29
.
15.
Nasr-El-Din
,
H. A.
,
Taylor
,
K. C.
, and
Al-Hajji
,
H. H.
, 2002, “
Propagation of Cross-Linkers Used in In-Situ Gelled Acids in Carbonate Reservoirs
,”
SPE/DOE Improved Oil Recovery Symposium held in Tulsa, OK
, Apr. 13–17, SPE 75257.
16.
Amro
,
M. M.
, 2006, “
Extended Matrix Acidizing Using Polymer-Acid Solutions
,”
SPE Technical Symposium of Saudi Arabia Section
, Dhahran, Saudi Arabia, May 21–23, SPE 106360.
17.
Taylor
,
K. C.
,
Al-Ghamdi
,
A. H.
, and
Nasr-El-Din
,
H. A.
, 2004, “
Effect of Additives on the Acid Dissolution Rates of Calcium and Magnesium Carbonates
,”
SPE Prod. Facil.
,
19
(
3
), pp.
122
127
.
18.
Lynn
,
J. D.
, and
Nasr-El-Din
,
H. A.
, 2001, “
A Core-Based Comparison of the Reaction Characteristics of Emulsified and In-Situ Gelled Acids in Low Permeability, High Temperature, Gas Bearing Carbonates
,”
SPE International Symposium on Oilfield Chemistry
, Houston, TX, Feb. 13–16, SPE 65386.
19.
Bazin
,
B.
,
Roque
,
C.
,
Chauveteau
,
G. A.
, and
Boute
,
M. J.
, 1999, “
Acid Filtration Under Dynamic Conditions to Evaluate Gelled Acid Efficiency in Acid Fracturing
,”
SPE J.
,
4
(
4
), pp.
360
367
.
20.
Taylor
,
K. C.
, and
Nasr-El-Din
,
H. A.
, 2002, “
Core Flood Evaluation of In-Situ Gelled Acid
,”
SPE International Symposium and Exhibition on Formation Damage
, Lafayette, LA, Feb. 20–21, SPE 73707.
21.
Welton
,
T. D.
, and
Van Domelen
,
M. S.
, 2008, “
High-Viscosity-Yield Acid Systems for High-Temperature Stimulation
,”
SPE Prod. Oper.
,
23
(
2
), pp.
177
183
.
22.
Gomaa
,
A. M.
, and
Nasr-El-Din
,
H. A.
, 2010, “
New Insights into the Viscosity of Polymer-Based In-Situ Gelled Acids
,”
SPE Prod. Oper.
,
25
(
3
), pp.
367
375
, SPE 121728-PA.
23.
Gomaa
,
A. M.
,
Mahmoud
,
M. A.
, and
Nasr-El-Din
,
H. A.
, 2011, “
Effect of Shear Rate on the Propagation of Polymer-Based In-Situ-Gelled Acids Inside Carbonate Cores
,”
SPE Prod. Oper.
,
26
(
1
), pp.
41
54
.
24.
Al-Ghamdi
,
A. H.
,
Mahmoud
,
M. A.
,
Hill
,
A. D.
, and
Nasr-El-Din
,
H. A.
, 2009, “
Diversion and Propagation of Viscoelastic Surfactant-Based Acid in Carbonate Cores
,”
SPE International Symposium on Oilfield Chemistry
, The Woodlands, TX, Apr. 20–22, SPE 121728.
25.
Hill
,
A. D.
,
Zhu
,
D.
, and
Wang
,
Y.
, 1995, “
The Effect of Wormholing on the Fluid-Loss Coefficient in Acid Fracturing
,”
SPE Prod. Facil.
,
10
(
4
), pp.
257
264
.
You do not currently have access to this content.