Using the Hollow-Core Test To Determine Acid Reaction Rates

1986 ◽  
Vol 1 (02) ◽  
pp. 111-116 ◽  
Author(s):  
R.D. Gdanski ◽  
L.R. Norman
Keyword(s):  
Reaction Rates ◽  
Hollow Core ◽  
Acid Reaction

The Effect of Surface Kinetics in Fracture Acidizing

1974 ◽  
Vol 14 (04) ◽  
pp. 385-395 ◽  
Author(s):  
L.D. Roberts
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Mass Transfer ◽  
Reaction Rates ◽  
Graphical Form ◽  
Mixing Coefficient ◽  
Acid Reaction ◽  
The Mathematical Model ◽  
Plate System ◽  
Acid Leakoff

Abstract A mathematical model is developed that yields the distance to which live aid may penetrate into a fracture under conditions in which the over-all reaction kinetics. The model is solved by an explicit finite-difference method, and the results are presented in graphical form. An example design presented in graphical form. An example design calculation is given for HC1 reaction in a dolomite fracture. Experimental data are presented for acid flow in limestone and dolomite laboratory - prepared fracture systems 4.1 t 9.7 ft long, at 71, 190, and 290F. From these experiments was determined a parameter appearing in the mathematical model-termed the effective mixing coefficient. The mixing coefficient has a minimum in the low Reynolds number region, indicating that rectilinear laminar flow is approached more closely just before the flow becomes turbulent. The mixing coefficient also appears to be dependent upon temperature in the laminar flow region. The mathematical solutions given in this paper are applicable to situations in which the over-all rate of acid reaction is not determined solely by mass transfer. Introduction Acids are widely used in the hydraulic fracturing of reservoirs to stimulate wells. Roughly speaking, the purpose of the acid is to selectively react with and dissolve portions of the fracture wall so that a finite fluid conductivity remains when the well is returned to production. One important variable that must be known in designing these acid fracturing treatments is the distance to which acid will penetrate the fracture before completely reacting penetrate the fracture before completely reacting and becoming spent. This distance is usually termed the acid penetration length and is an essential part of the information needed for predicting productivity after acidizing. Other important design variables include the dynamic fracture geometry and the residual fracture conductivity. Because of its importance in predicting stimulation ratios, acid penetration into a fracture has been studied by several investigators. Both static tests and dynamic tests have been used to predict acid reaction rates in fractures. It seems predict acid reaction rates in fractures. It seems reasonable that a dynamic acid reactor test will be useful for predicting acid spending rates, since the mass transfer rate in an actual fracture may be approached in this type of test. One experimental apparatus used for acid flow tests in parallel plate system such as that used by Barron et al. plate system such as that used by Barron et al. and by Williams and Nierode. In these tests, acid is pumped at a known flow rate through a fracture of known geometry and the inlet and outlet acid composition is measured. From the resulting information it is possible to predict acid penetration in a real fracture with the aid of a mathematical model having experimentally determined parameters. We present here the results of an investigation of the use of mathematical model for predicting acid spending a fracture. Using Williams and Nierode's approach to calculating acid penetration, we have extended their method to allow for the fact that the surface reaction rates of several acid-rock systems (e.g., HC1-dolomite) may be finite compared with the rate of mass transfer to the surface. Experimental data are presented for determining the parameters appearing in the mathematical model and a sample calculation illustrates its use. MATHEMATICAL MODEL FOR ACID FRACTURING The mathematical model presented here is a modification of that introduced by Williams and Nierode to allow for the occurrence of finite reaction rates. This modification makes it possible to calculate theoretical penetration distances for acid featuring when reaction kinetics are important as in the case of the HC1-dolomite reaction. Since an analytical solution of the model is not possible, a finite-difference method was developed and is presented in Appendix A. presented in Appendix A. The model for acid formula is fracturing is presented in Fig. 1. Here the acid leakoff velocity, presented in Fig. 1. Here the acid leakoff velocity, is assumed constant over the fracture length. SPEJ p. 385

BiOBr photocatalyzed decarboxylation of glutamic acid: reaction rates, intermediates and mechanism

RSC Advances ◽  
2015 ◽  
Vol 5 (69) ◽  
pp. 55727-55730 ◽  
Author(s):  
Yanfen Fang ◽  
Hongwei Yang ◽  
Wei Zhou ◽  
Yue Li ◽  
David M. Johnson ◽  
...  
Keyword(s):  
Glutamic Acid ◽  
Succinic Acid ◽  
Reaction Rates ◽  
Direct Oxidation ◽  
Acid Reaction

BiOBr-photocatalyzed degradation of glutamic acid starts from the direct oxidation of the amino-carboxyl end and leads initially to succinic acid. Both the O-atoms from O2 and H2O incorporate into this product.

Anomalous Acid Reaction Rates in Carbonate Reservoir Rocks

SPE Journal ◽  
2006 ◽  
Vol 11 (04) ◽  
pp. 488-496 ◽  
Author(s):  
Kevin C. Taylor ◽  
Hisham A. Nasr-El-Din ◽  
Sudhir Mehta
Keyword(s):  
Saudi Arabia ◽  
Rotating Disk ◽  
Reaction Rates ◽  
Carbonate Reservoir ◽  
Reservoir Rock ◽  
Acid Dissolution ◽  
Gas Reservoir ◽  
Dissolution Rates ◽  
Reservoir Rocks ◽  
Acid Reaction

Summary It is generally assumed that the reaction of acid with limestone reservoir rock is much more rapid than acid reaction with dolomite reservoir rock. This work is the first to show this assumption to be false in some cases, because of mineral impurities commonly found in these rocks. Trace amounts of clay impurities in limestone reservoir rocks were found to reduce the acid dissolution rate by up to a factor of 25, to make the acid reactivity of these rocks similar to that of fully dolomitized rock. A rotating disk instrument was used to measure dissolution rates of reservoir rock from a deep, dolomitic gas reservoir in Saudi Arabia (275°F, 7,500 psi). More than 60 experiments were made at temperatures of 23 and 85°C and HCl concentration of 1.0 M (3.6 wt%). Eight distinctly different rock types that varied in composition from 0 to 100% dolomite were used in this study. In addition, the mineralogy of each rock disk was examined before and after each rotating disk experiment with an environmental scanning electron microscope (ESEM) using secondary and backscattered electron imaging and energy dispersive X-ray (EDS) spectroscopy. Acid reactivity was correlated with the detailed mineralogy of the reservoir rock. It was also shown that bulk anhydrite in the rock samples was converted to anhydrite fines by the acid at 85°C, a potential source of formation damage. Introduction A study of acid reaction rates and reaction coefficients of a dolomitic reservoir rock was recently reported by Taylor et al. (2004a). In that work, it was found that reaction rates depended on mineralogy and the presence of trace components such as clays. This paper examines in detail the relationship between acid reactivity and mineralogy of a deep, dolomitic gas reservoir rock. An accurate knowledge of acid reaction rates of deep gas reservoirs can contribute to the success of matrix and acid fracture treatments. Many studies of acid stimulation treatments of Formation K, a deep, dolomitic gas reservoir in Saudi Arabia, have been published (Nasr-El-Din et al. 2001, 2002a, 2002b; Bartko et al. 2003). It is generally assumed that the reaction of acid with limestone reservoir rock is much more rapid than acid reaction with dolomite reservoir rock during acidizing treatments. However, much of the reported data were obtained with pure limestones, dolomites, and marbles. These include calcite marble (CaCO3) (Lund et al. 1975; de Rozieres 1994; Frenier and Hill 2002), dolomite marble [CaMg(CO3)2] (Lund et al. 1973; Herman and White 1985), Indiana limestone (Mumallah 1991), St. Maximin and Lavoux limestones (Alkattan et al. 1998), Haute Vallée de l'Aude dolomite (Gautelier et al. 1999), Bellefonte dolomite (Herman and White 1985), San Andres dolomite (Anderson 1991), Kasota dolomite (Anderson 1991), and Khuff dolomite reservoir cores (Nasr-El-Din et al. 2002b). The effects of common acid additives on calcite and dolomite dissolution rates were reported in detail (Frenier and Hill 2002; Taylor et al. (2004b; Al-Mohammed et al. 2006). The effects of impurities such as clays on rock dissolution have not been reported.

Measurement of Acid Reaction Rates with the Rotating Disk Apparatus

2009 ◽  
Vol 48 (06) ◽  
pp. 66-70 ◽  
Author(s):  
K.C. Taylor ◽  
H.A. Nasr-El-Din
Keyword(s):  
Rotating Disk ◽  
Reaction Rates ◽  
Acid Reaction

Measurement of Acid Reaction Rates of a Deep Dolomitic Gas Reservoir

2004 ◽  
Vol 43 (10) ◽  
Author(s):  
K.C. Taylor ◽  
A.H. Al-Ghamdi ◽  
H.A. Nasr-El-Din
Keyword(s):  
Reaction Rates ◽  
Gas Reservoir ◽  
Acid Reaction

The Evaluation and Introduction of Novel Acid-Based Crosslinked Gel for HPHT Acid Fracturing Applications in Carbonate Formations

2022 ◽  
Author(s):  
Khalid Fahad Almulhem ◽  
Ataur Malik ◽  
Mustafa Ghazwi
Keyword(s):  
Traditional Approach ◽  
Reaction Rates ◽  
Field Trials ◽  
Gas Production ◽  
Carbonate Reservoir ◽  
Fluid System ◽  
Acid Fracturing ◽  
Acid Reaction ◽  
Carbonate Formations

Abstract Acid Fracturing has been one of the most effective stimulation technique applied in the carbonate formations to enhance oil and gas production. The traditional approach to stimulate the carbonate reservoir has been to pump crosslinked gel and acid blends such as plain 28% HCL, emulsified acid (EA) and in-situ gelled acid at fracture rates in order to maximize stimulated reservoir volume with desired conductivity. With the common challenges encountered in fracturing carbonate formations, including high leak-off and fast acid reaction rates, the conventional practice of acid fracturing involves complex pumping schemes of pad, acid and viscous diverter fluid cycles to achieve fracture length and conductivity targets. A new generation of Acid-Based Crosslinked (ABC) fluid system has been deployed to stimulate high temperature carbonate formations in three separate field trials aiming to provide rock-breaking viscosity, acid retardation and effective leak-off control. The ABC fluid system has been progressively introduced, initially starting as diverter / leak off control cycles of pad and acid stages. Later it was used as main acid-based fluid system for enhancing live acid penetration, diverting and reducing leakoff as well as keeping the rock open during hydraulic fracturing operation. Unlike in-situ crosslinked acid based system that uses acid reaction by products to start crosslinking process, the ABC fluid system uses a unique crosslinker/breaker combination independent of acid reaction. The system is prepared with 20% hydrochloric acid and an acrylamide polymer along with zirconium metal for delayed crosslinking in unspent acid. The ABC fluid system is aimed to reduced three fluid requirements to one by eliminating the need for an intricate pumping schedule that otherwise would include: a non-acid fracturing pad stage to breakdown the formation and generate the targeted fracture geometry; a retarded emulsified acid system to achieve deep penetrating, differently etched fractures, and a self-diverting agent to minimize fluid leak-off. This paper describes all efforts behind the introduction of this novel Acid-Based Crossliked fluid system in different field trials. Details of the fluid design optimization are included to illustrate how a single system can replace the need for multiple fluids. The ABC fluid was formulated to meet challenging bottom-hole formation conditions that resulted in encouraging post treatment well performance.

Measurement of Acid Reaction Rates of a Deep Dolomitic Gas Reservoir

2003 ◽  
Author(s):  
K.C. Taylor ◽  
A.H. Al-Ghamdi ◽  
H.A. Nasr-El-Din
Keyword(s):  
Reaction Rates ◽  
Gas Reservoir ◽  
Acid Reaction
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