A New Finding in the Interaction Between Chelating Agents and Carbonate Rocks During Matrix Acidizing Treatments

Author(s):  
Ahmed Issam Assem ◽  
Hisham A. Nasr-El-Din ◽  
Corine De Wolf
SPE Journal ◽  
2011 ◽  
Vol 16 (03) ◽  
pp. 559-574 ◽  
Author(s):  
M.A.. A. Mahmoud ◽  
H.A.. A. Nasr-El-Din ◽  
C.A.. A. De Wolf ◽  
J.N.. N. LePage ◽  
J.H.. H. Bemelaar

Summary Matrix acidizing is used in carbonate formations to create wormholes that connect the formation to the wellbore. Hydrochloric acid (HCl), organic acids, or mixtures of these acids are typically used in matrix-acidizing treatments of carbonate reservoirs. However, the use of these acids in deep wells has some major drawbacks, including high and uncontrolled reaction rates and corrosion to well tubulars, especially those made of chromium-based tubulars (Cr-13 and duplex steel); and these problems become severe at high temperatures. To overcome problems associated with strong acids, chelating agents were introduced and used in the field. However, major concerns with most of these chemicals are their limited dissolving power and negative environmental impact. L-glutamic acid diacetic acid (GLDA), a newly developed environmentally friendly chelate, was examined as a replacement for acid treatments in deep oil and gas wells. The solubility of calcium carbonate (CaCO3) in the new chelate was measured over a wide range of parameters. Coreflood tests were conducted using long Indiana limestone cores 1.5 in. in diameter and 20 in. in length, which allowed better understanding of the propagation of this chemical in carbonate rocks. The cores were X-ray scanned before and after the injection of chelate solutions into the cores. The concentration of calcium (Ca) and chelate was measured in the core effluent samples. To the best of our knowledge, this is the first study to examine the fate and propagation of chelating agents in coreflood studies. GLDA has a very good ability to dissolve Ca from carbonate rocks over a wide pH range by a combination of acid dissolution and chelation. The addition of 5 wt% sodium chloride (NaCl) did not affect the GLDA performance at pH = 13 but significantly accelerated the reaction at pH = 1.7. Compared with other chelating agents, GLDA dissolved more Ca than ethanoldiglycinic acid (EDG) but less than hydroxyethyl ethylenediamine triacetic acid (HEDTA) at high pH values. GLDA of pH = 1.7 was able to form wormholes at 2 and 3 cm3/min. GLDA was found to be thermally stable at temperatures up to 350°F.


Petroleum ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 67-76 ◽  
Author(s):  
Mian Umer Shafiq ◽  
Hisham Khaled Ben Mahmud ◽  
Mohsen Ghasemi

2018 ◽  
Author(s):  
Emil Panait ◽  
Constantin Isac ◽  
Csaba Marton ◽  
Arlinda Dos Santos ◽  
Stefano Girardi

2015 ◽  
Author(s):  
T. T. Bekibayev ◽  
I. K. Beisembetov ◽  
B. K. Assilbekov ◽  
A. B. Zolotukhin ◽  
U. K. Zhapbasbayev ◽  
...  

2019 ◽  
Vol 9 (4) ◽  
pp. 2793-2809 ◽  
Author(s):  
Mian Umer Shafiq ◽  
Hisham Khaled Ben Mahmud ◽  
Muhammad Khurram Zahoor ◽  
Arshad S. A. Shahid ◽  
Reza Rezaee ◽  
...  

SPE Journal ◽  
2019 ◽  
Vol 24 (05) ◽  
pp. 2163-2181 ◽  
Author(s):  
W.. Wei ◽  
A.. Varavei ◽  
A.. Sanaei ◽  
K.. Sepehrnoori

Summary Matrix acidizing is a widely used stimulation process during which acid is injected into the formation at pressures that are less than the fracturing pressure. The purpose of matrix acidizing is to improve formation permeability or to bypass damaged zones through rock dissolution. Because of precipitation and diagenesis, carbonate rocks might contain different compositions, including calcite (CaCO3), dolomite [CaMg(CO3)2], and other minerals. When acid is injected into the formation, reactions between acid and multiple minerals of carbonate rocks occur simultaneously. In this paper, a two–scale continuum model is implemented in UTCOMP, a 3D compositional reservoir simulator, coupled with IPhreeqc, a generalized code of PHREEQC as a module. PHREEQC is an open–source program that performs a wide variety of geochemical calculations (Charlton and Parkhurst 2011). For the UTCOMP/IPhreeqc coupled model, the two–scale continuum model describes the mechanisms of convection and dispersion, whereas IPhreeqc is used for the calculation of reactions between aqueous phase and minerals. We have validated the simulation model through comparison with the analytical solution. We also compared the UTCOMP/IPhreeqc coupled model with a simple–reaction model, in which the reaction is assumed to be a first–order reaction between acid and calcite, by modifying the IPhreeqc database to obtain consistent results. On this basis, we have investigated the effects of mineral compositions on acidizing efficiency and the wormhole–propagation process. It is found that mineralogy heterogeneity is a key factor that affects acidizing efficiency and the dissolution structure. This work contributes to simulating the acidizing process with complex geochemical reactions considering the chemistry of the aqueous solution interacting with minerals. The presented model improves our understanding of carbonate–acidizing optimization.


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