Slaying the Myth of Infinite Reactivity of Carbonates

Gdanski, Rick; Domelen, Mary Susan Van

doi:10.2118/50730-ms

Cited by 13 publications

(10 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A temperature survey performed subsequent to the acid treatment indicated the temperature was 158 o F, and the falloff test indicated a BHST of 156 o F. The Arab-D is a dolomitic limestone, and dolomite reacts with HCl under surface reaction kinetics at a temperature less than 175 o F. 16 Recently it was reported that the energy of activation of dolomite was twice that of limestone. 25 This is indicative of a slower reaction, which is supported in the literature. 1 Thus, the acid may preferentially bypass the dolomite and wormhole through the limestone to create deeper penetration.…”

Section: Resultssupporting

confidence: 75%

Field Validation of a Carbonate Matrix Acidizing Model: A Case Study of Seawater Injection Wells in Saudi Arabia

Thomas¹,

Nasr-El-Din²

2003

Proceedings of SPE European Formation Damage Conference

View full text Add to dashboard Cite

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAlthough hydrochloric acid has been used for more than 60 years to matrix acidize carbonate reservoirs, the process is still as much art as science. Historically, design engineers have used a "rule-of-thumb" based on field experience to quantify the design parameters for a candidate well. However, each well is different and this "generic" approach for treatment design can result in under-or over-treating. This paper is directed at matrix acidizing of vertical water injection wells completed in a heterogeneous carbonate reservoir (Arab-D) in Saudi Arabia with focus on field validation of a commercial matrix acidizing design simulator. The "validation" process allows the production engineer to "calibrate" the simulator for his specific field, and use it with confidence to improve treatment designs.In this field study three matrix-acidized injection wells were used for validation of the carbonate acidizing model. The wells were completed in 150 to 200 feet openhole intervals in a reservoir composed of a variety of limestone -dolomite mixtures. Treatments were performed using hydrochloric acid along with particulate diverter stages, which was bullheaded down casing. The post-treatment model validation process consisted of simulation of the actual treatment using various values of "acidizing efficiency" to yield an acceptable match with the final skin. Subsequently, a comparison of the simulated and actual surface treating pressure, and the prepost-treatment wellhead pressure during seawater injection was made. A detailed description of the validation process and the supporting well data are presented.A good match of predicted surface pressure and actual wellhead pressure obtained from the treating report adds credibility to the simulator. Normally, the difference in actual and simulated pressure was less than 10%. Pressure data indicate that the benzoic acid/rock salt diverter systems were inefficient. The simulator indicates diverter inefficiency causes the high permeability zones to become "thief zones" resulting in non-uniform acid distribution. In all cases the pressure dropped 25 to 50% within ten minutes following injection of acid into the formation. An internal acidizing efficiency factor was increased to allow the predicted skin of the simulator to approximate the actual skin determined from a falloff test. It was discovered that the optimum efficiency factor was a function of the amount of dolomite in the reservoir. Guidelines for the determination of the efficiency factor based upon mineralogy are presented along with an explanation for this and other observations.

show abstract

Section: Resultssupporting

confidence: 75%

Field Validation of a Carbonate Matrix Acidizing Model: A Case Study of Seawater Injection Wells in Saudi Arabia

Thomas¹,

Nasr-El-Din²

2003

Proceedings of SPE European Formation Damage Conference

View full text Add to dashboard Cite

show abstract

“…Although the implications of these results for acidizing treatments were evaluated, the underlying cause was not addressed. Reaction rate reduction caused by clays will be discussed in this paper that can explain the results reported by Gdanski and van Domelen (1999).…”

Section: Introductionmentioning

confidence: 59%

“…Anderson showed that significant variations in reactivity existed, but did not explain or investigate the results. Gdanski and van Domelen (1999) reported that carbonate reservoir rocks were often significantly less reactive at reservoir conditions than would be expected from reactivity data reported for pure calcite marble and dolomite marble as given by Lund et al (1973Lund et al ( , 1975. Although the implications of these results for acidizing treatments were evaluated, the underlying cause was not addressed.…”

Section: Introductionmentioning

confidence: 98%

Anomalous Acid Reaction Rates in Carbonate Reservoir Rocks

2006

View full text Add to dashboard Cite

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.

show abstract

“…This instrument has been used extensively to investigate the reaction of HCl, organic acids, and chelating agents with carbonate rocks (Hansford and Litt 1968;Lund et al 1975;de Rozieres et al 1994;Fredd and Fogler 1998a, 1998b, 1998cFredd 1998;Conway et al 1999;Gautelier et al 1999;Gdanski and Van Domelen 1999;Frenier and Hill 2002;Taylor et al 2004aTaylor et al , 2004bTaylor et al , 2006Alkattan et al 1998Alkattan et al , 2002Al-Mohammad et al 2006;Al-Khaldi et al 2007;Nasr-El-Din et al 2008b). It has also been used to study mass and heat transfer in non-Newtonian fluids (Hansford and Litt 1968;de Rozieres et al 1994;Al-Mohammad et al 2006;Nasr-El-Din et al 2008b).…”

Section: Introductionmentioning

confidence: 99%

Quantitative Analysis of Reaction-Rate Retardation in Surfactant-Based Acids

Nasr‐El‐Din

Al-Mohammed

Al-Aamri

et al. 2009

SPE Production &Amp; Operations

View full text Add to dashboard Cite

Fracture acidizing has been a dominant practice in the industry to enhance well productivity in low-permeability carbonate reservoirs. Many acid systems have been developed to improve this stimulation process. The most desirable characteristics for an acid system to be suitable for fracture acidizing are leakoff control and retarded reaction rate. These characteristics are required for deep acid penetration, so that when the fracture closes, long flow channels are etched on the fracture surfaces. Leakoff control can be achieved by pumping a pad containing a viscosifying agent or solid bridging agents to plug wormholes generated by acid dissolution. Reaction retardation is attempted usually by lowering the effective diffusivity of the hydrogen ion.It is well known that during an acid-fracturing operation, the overall reaction rate of hydrochloric acid (HCl) with limestone is mass-transfer-limited. Designing the treatment requires knowing the effective diffusivity of the hydrogen ion in the acid system, which, to the best of the authors' knowledge, has not been determined before. Because of their combined leakoff-control and retardation capabilities, surfactant-based acids have been used in acid-fracturing treatments. Because more carbonate reservoirs are treated by use of this acid system, it is important to obtain the effective diffusivity of H + .The rotating-disk device has been used to investigate the reaction kinetics between a reactive solution and carbonate rocks because the thickness of the boundary layer is uniform throughout the disk surface. This paper discusses the reaction-rate data generated recently for surfactant-based acid by use of a rotating-disk apparatus and presents the methodology used to determine the effective diffusivity from the measurements.The results obtained indicated that the viscoelastic surfactant examined (carboxybetaine-type) reduced the dissolution rate of calcite with HCl acid. The surfactant reduced the diffusion coefficient for H + . The effect of temperature on the diffusion coefficient did not follow the Arrhenius law.

show abstract

Slaying the Myth of Infinite Reactivity of Carbonates

Cited by 13 publications

References 15 publications

Field Validation of a Carbonate Matrix Acidizing Model: A Case Study of Seawater Injection Wells in Saudi Arabia

Field Validation of a Carbonate Matrix Acidizing Model: A Case Study of Seawater Injection Wells in Saudi Arabia

Anomalous Acid Reaction Rates in Carbonate Reservoir Rocks

Quantitative Analysis of Reaction-Rate Retardation in Surfactant-Based Acids

Contact Info

Product

Resources

About