Aluminum Scaling and Formation Damage due to Regular Mud Acid Treatment

Nasr‐El‐Din, Hisham A.; Hopkins, John A.; Shuchart, Chris E.; Wilkinson, Tim

doi:10.2118/39483-ms

Cited by 33 publications

(11 citation statements)

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“…However, chemical analysis of well flow back in different fields show high levels of iron, even after the preflush stage. 27,28 Based on these field data and the results obtained from this study, iron precipitation should be considered in modeling matrix acidizing of sandstone formations.…”

Section: Impact On Field Applicationmentioning

confidence: 79%

Iron Precipitation During Acid Treatments Using HF-Based Acids

Nasr‐El‐Din

Al-Dahlan

As-Sadlan

et al. 2002

International Symposium and Exhibition on Formation Damage Control

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDescription of the Paper: Iron precipitation during spending of four HF-based acids was examined using an experimental procedure similar to that of Taylor et al. 1,2 Regular mud acid (HCl:HF weight ratios of 12/3 and 6/1.5) and three retarded HF acids based on AlCl 3 , boric acid, and a phosphonic acid were examined. Iron (III) was added to these acids at concentrations of 1,000 and 10,000 mg/L and the acid neutralization tests were conducted using sodium carbonate at ambient conditions. Results, Observations, Conclusions:For full strength regular mud acid, the onset of iron precipitation occurred at pH 0.6, and complete precipitation of iron occurred at pH 1. These values are lower than those noted with 15 wt% HCl. Values of pH at the onset and complete precipitation of iron were found to be a function of initial HF acid concentration. For the retarded HF acid based on AlCl 3 , aluminum compounds (sodium hexafluoroaluminate) precipitated at all pH values examined, while iron compounds (sodium hexafluoroferrate) precipitated at pH values that depended on initial iron (III) and HF acid concentrations. For the retarded HF acid based on boric acid, iron compounds precipitated at pH values similar to those noted with 15 wt% HCl. For the retarded HF acid based on phosphonic acid, iron compounds precipitated over a narrow pH range (4.7-5.3) because of the chelating characteristics of the phosphonic acid.Applications: Sandstone formations are commonly acidized using an HF-based acid system. Precipitation of iron compounds during acid treatments can cause formation damage by plugging the formation and stabilizing acid/oil sludges. Unlike acid treatments using HCl, previous studies on iron control with HF-based acids are sparse. These new findings reflect the complex chemical interactions that occur with various HF-based acid systems. They will be used to better control iron precipitation during acid stimulations of sandstone reservoirs.Technical Contributions: 1. Iron precipitation in the presence of various HF-based acids was identified. 2. Precipitation of aluminum and iron compounds was noted with the retarded HF acid based on AlCl 3 . 3. Iron precipitation in the presence of boric acid was similar to that noted with 15 wt% HCl, and 4. Minimal iron precipitation was noted over a narrow pH range with the HF acid based on phosphonic acid.

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Section: Impact On Field Applicationmentioning

confidence: 79%

Iron Precipitation During Acid Treatments Using HF-Based Acids

Nasr‐El‐Din

Al-Dahlan

As-Sadlan

et al. 2002

International Symposium and Exhibition on Formation Damage Control

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“…[14][15]18,20 Primarily, limestone (CaCO 3 ) reacts at high reaction rate with hydrochloric acid (HCl) and moderately with formic acid and acetic acids but dolomite (CaMg[CO 3 ] 2 ) reacts slow and less. [20][21] The reaction rate of acid (HCl) in sandstone mainly depends on the carbonate content within the sandstone minerals. However, the silicon dioxide, clay and silt can not react with hydrochloric acid (HCl).…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, Hydrofluoric acid (HF) has only the ability to dissolve the silicon dioxide, clay and silt at different level of strength power. [20][21] Due to chemical reaction of HF acid with clays, silt and sandstone, it has effectively used as a formation damage removal. In addition, the by-product of HF acid reaction with sandstone is complex and critical with insoluble precipitations of calcium fluoride (CaF 2 ), sodium hexaflourosilicate (Na 2 SiF 6 ), hydrated silica (SiO 2 .2H 2 O) and potassium hexaflourosilicate (K 2 SiF 6 ).…”

Section: Introductionmentioning

confidence: 99%

“…In addition, the by-product of HF acid reaction with sandstone is complex and critical with insoluble precipitations of calcium fluoride (CaF 2 ), sodium hexaflourosilicate (Na 2 SiF 6 ), hydrated silica (SiO 2 .2H 2 O) and potassium hexaflourosilicate (K 2 SiF 6 ). [20][21]12 Due to the limitation of water handling system, a recommendation was obtained to stimulate the existed water disposal wells to enhance the well injectivity especially well with a injectivity decline such as DW-4 well. This well was tested with low injectivity rate even it is newly drilled well with a horizontal section, the injection test was applied in order to cover the requested rate.…”

Section: Introductionmentioning

confidence: 99%

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Lessons Learned from Using New Chemical Recipe for Acid Stimulation in Water Disposal Wells (Al-Khafji Field)

2012

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Acid treatments for dolomite formation with low permeability differ from that applied for calcite rock. Unlike limestone acidizing where HCl reacts with limestone in rapid reaction rate to generate reaction products soluble in water. In Some cases, injectivity well can not effectively improve in dolomite formation with low permeability using conventional 15 wt% HCl acid. In addition, formation damage due to drilling or workover operations can not be removed. Therefore, the process of treating dolomite for injectivitiy improvement may consider a serious issue for acid stimulation. The challenges of dolomite acidizing are to optimize damage removal while maximizing rock permeability with wormhole occurrences. Well DW-4 drilled and completed as horizontal open hole wastewater disposal wells for excess water production from offshore oil wells in Al-Khafji Field. This well is used to dispose the un-wanted co-produced water which shows injectivity decline with time due to sand plugging and oil content droplet.Several acid stimulation treatments were conducted on subject well with low rate of success due to not considering the dolomite reaction rate and the chemical volume to be used. A simple previous treatment review was conducted to select the best chemical recipe and treatment volume for injectivity improvement . As a result of conducting new chemicals recipe with optimum treatment volume, a major improvement in well injectivity with formation damage removal was obtained. This paper demonstrated new design methodology with extensive field study to address the challenges and the best future operation practices for acid stimulation. It included a pre-flush of mutual solvents, then bullheading stage of 20 wt% HCl with intensifier to accelerate the chemical reaction with dolomite rock.A carefully designed train of treatment fluids was applied to remove formation damage induced by drilling and injection fluids. Injectivity tests before and after each step of the treatment was recorded and evaluated. Proper design and execution of the stimulation treatment almost doubled the well injectivity index. Challenges, fluid selection, design criteria, field treatment, lessons learned, and results of the acid treatments were discussed in this paper.

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“…Hydrated silica, Si(OH) 4 , is formed during the secondary and tertiary reactions of HF with feldspar and clay as shown in Eqs. 1 and 2, respectively (Gdanski 1994;Nasr-El-Din et al 1998;Shuchart 1995;Crowe 1986). …”

Section: Introductionmentioning

confidence: 99%

Matrix Acid Systems for Formations With High Clay Content

Jaramillo

Romero

Ortega

et al. 2010

SPE International Symposium and Exhibition on Formation Damage Control

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There are a number of sandstone reservoirs in which more than 50% of the matrix is composed of clay and feldspar minerals. Typically, these reservoirs are subject to fines migration and respond poorly to conventional matrix acid stimulation treatments. There are numerous challenges when treating these formations: the removal and/or stabilization of the mobile fines in the pore spaces without destabilizing the clays in the matrix or the matrix itself; the need to stimulate the formation some distance away from the wellbore, and, equally importantly, to minimize reaction products precipitating in the matrix; and the very low critical velocities that can lead to plugging while injecting the treatment. In many conventional acid treatments, after an initially good response to the treatment, the production falls to levels similar to or lower than before the treatment. A common compromise is to empirically adjust the strength of a HF/HCl acid system used to treat a particular formation, so as to delay the onset of renewed fines migration after the treatment for as long as possible, at the expense of optimizing productivity. In many cases this results in making the treatments uneconomic.To meet theses challenges a new fluoroboric acid system has been developed. The basic chemistry used is similar to that of a retarded HF acid previously described in the literature as clay acid (Thomas and Crowe 1978). . However, unlike the retarded HF acid, the new fluid uses organic acid as a chelant and is effectively a blend of organic/fluoroboric acid and hence an organic clay acid. The fluoroboric acid is generated by the addition of hydrofluoric and boric acid. By adjusting the initial concentration and ratio of hydrofluoric and boric acid, it is possible to optimize the stimulation effect of the treatment in a particular formation and prevent future fines migration. A key is the initial concentration of free hydrofluoric acid and the available hydrofluoric acid from hydrolysis of the fluoroboric acid with respect to the clay mineralogy and temperature. The concentration of the organic acid, the chelant, is also adjusted based on an analysis of the effluent during core flow testing, to minimize precipitation.Prior to customizing the organic clay acid system, treatments were performed in low temperature (< 140 o F) reservoirs, with 30% kaolinite along with zeolite and chlorite present in the formation matrix. While there was a noted stimulation effect and fines stabilization, the initial post-treatment productivity fell short of that seen using an organic mud acid. In the case of organic mud acid, however, the production declined rapidly, indicating renewed fines migration. This led to a reformulation of the organic clay acid for use as the main treating fluid, eliminating the need for HF preflushes. The initial productivity of wells treated using the reformulated organic clay acid were higher than that obtained using an organic mud acid and remained stable, indicating effective fines migration control.In contrast to what might be e...

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Aluminum Scaling and Formation Damage due to Regular Mud Acid Treatment

Cited by 33 publications

References 0 publications

Iron Precipitation During Acid Treatments Using HF-Based Acids

Iron Precipitation During Acid Treatments Using HF-Based Acids

Lessons Learned from Using New Chemical Recipe for Acid Stimulation in Water Disposal Wells (Al-Khafji Field)

Matrix Acid Systems for Formations With High Clay Content

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