Delayed-Release Acid System for Cleanup of Al Khalij Horizontal Openhole Drains

Leschi, Pierre; Demarthon, Gilles; Davidson, Eric; Clinch, Duncan

doi:10.2118/98164-ms

Cited by 36 publications

(8 citation statements)

References 9 publications

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“…To assure the longest possible reaction delay, the acid precursor is introduced just before injection into the well. The operating mechanism of this system and some results of its application are presented in a number of papers (Leschi et al 2006;Davidson et al 2012).…”

Section: Systems For Removal Of Filter Cake In Delayed Reaction Modementioning

confidence: 99%

Uranium Wells: The Proper Selection of Drilling Mud and Completion Fluid Has Changed All the Rules of the Game

et al. 2015

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In Southern Kazakhstan, uranium ore is produced by the in-situ leaching (ISL) method. One of the uranium companies, which is producing in this manner experienced difficulties in attempting to increase yield when using bentonite-polymer mud and sodium hypochlorite for removing the filter cake. The company had additional objectives that included increased production cycle time and optimization of drilling technology to reduce well construction time.The design of a typical well is represented by a vertical shaft 215.9 mm in diameter and up to 500 m deep. The well is cased by plastic pipes with a filter lining in the pay zone interval. Bottomhole temperature is in the 25-28°C range.A three-stage concept has been proposed to complete these tasks: the use of inhibiting polyacrylamide (PAA)-based mud on the upper nonproductive intervals and a specialized mud system designed for completion of productive horizons, which includes only acid-soluble and biodegradable components. The final stage involves treating the reservoir with a filter cake removal system. Instead of sodium hypochlorite, an organic product has been proposed for the removal of the filter cake, exhibiting many advantages, such as increasing the reaction time for acid formation, deep penetration into the near-wellbore region, and guaranteed treatment of the entire interval, unlike conventional acids, which react instantaneously and are; therefore, inefficient in horizontal intervals.These technologies were successfully applied and have provided a number of benefits to the customer, including an increase in well productivity by 20% as compared to the adjacent wells and up to a 10-fold yield increase in wells with depleted reservoirs. Time to reaching the design yield decreased on average by 30% while reducing the total well commissioning time by an average of 10%.This article introduces some aspects of these technologies and the results of their application.

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Section: Systems For Removal Of Filter Cake In Delayed Reaction Modementioning

confidence: 99%

Uranium Wells: The Proper Selection of Drilling Mud and Completion Fluid Has Changed All the Rules of the Game

et al. 2015

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“…Ethyl-lactate ester has been included only in this research study for mainly two reasons. First, the generated lactic acid has strength similar to that of formic acid and both have dissociation constants that are about 10 times greater than that of acetic acid (Leschi et al, 2006). Secondly, the lactate ester hydrolysis reaction to lactic acid depends on the temperature and also the acid concentration increases gradually with time (Al Moajil et al, 2007).…”

Section: Conventional Filter Cake Clean-up Techniquesmentioning

confidence: 99%

Characteristics and Removal of Filter Cake Formed by Formate-Based Drilling Mud

Alotaibi

2008

SPE International Symposium and Exhibition on Formation Damage Control

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This mud typically contains XC-polymer, starch, polyanionic cellulose, and a relatively small amount of calcium carbonate particles, and is used to drill a deep sandstone reservoir (310°F). Calcium carbonate particles are frequently used as weighting material to maintain the pressure that is required for well control and minimize the leak-off. Such solids become consolidated and trapped in the polymeric material and this makes the filter cake a strong permeability barrier. The conventional method for cleaning the filter cake is by circulating solid-free formate brines at a high flow rate. This mechanical technique removes only the external drilling fluid damage. Citric acid at 10 wt%, formic acid, and lactic acid were found to be incompatible with formate brine at room temperature. However, these acids were compatible with formate brine at temperatures greater than 122°F. Only acetic acid was compatible with formate brine. A formula was developed that is compatible at room and reservoir temperature. This formula was effective in removing filter cake. A corrosion inhibitor was added to protect downhole tubulars. In general detail, this research will discuss the development of this formula and all tests that led to its development.

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“…15 The current available acid precursors are the in-situ formic, 16,17 acetic, 14,18 and lactic 15,19 acids. Nasr-El-Din, SPE, and A.D. Al-Aamri, Saudi Aramco slow reaction with the filter cake 14 and the total zonal coverage.…”

Section: Spe 107537mentioning

confidence: 99%

Evaluation of In-Situ Generated Acids for Filter-Cake Cleanup

Nasr‐El‐Din

Moajil

2007

European Formation Damage Conference

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fax 01-972-952-9435. AbstractFilter cake removal is a difficult task, especially in horizontal and extended reach wells. Water-based drilling fluids consist of xanthan gum as a viscosifier, starch as a fluid-loss control, sized calcium carbonate or salt particles to increase the mud density. Conventional chemical means used to remove filter cake are reactive mineral acids, enzymes, chelating agents, oxidizers, or combinations of these chemicals. Controlling of the reaction rate of the cleaning fluids with the filter cake material is an essential factor that determines the efficiency of filter cake removal.This study assesses the performance of three acid precursors (esters) that produce organic acids. These precursors produce low-molecular weight organic acids that can dissolve calcium carbonate particles from the filter cake. The rate of hydrolysis of acid precursors can be adjusted to produce a predetermine acid concentration at bottom hole conditions. Enzymes, mainly α-amylase, can be added to these esters to break starch that is present in the filter cake. The slow release of these weak organic acids ensures proper and efficient removal of the filter cake.Lab studies using static HPHT filter press indicated that the three systems can remove the filter cake efficiently. The rate of hydrolysis was measured for each system, and found to be a function of temperature and type and concentration of the acid precursor. Surface tension measurements conducted for solutions of the three precursors at different temperatures highlighted low surface tension values for the spent acids, which are needed to lift the spent acid following the treatment.No phase separation or precipitation was observed when the three systems were heated at temperatures up to 250°F. Surface tension measurements indicated that the formic acid system had low surface tension, which will accelerate lifting these fluids from tight formations. Acetic and lactic acid systems had much higher surface tension, and a suitable surfactant will be needed to reduce the surface tension. The kinetic study indicated the very rapid reaction rate of the precursor of formic acid and a moderate reaction rate in the acetic acid system. The reaction rate of the precursor of lactic acid was in between the two systems and more close to the in-situ acetic acid system.HPHT experiments showed that formic acid system was very efficient at short soaking times at temperatures of 200 and 250°F. The performance of lactic acid was comparable to formic acid when the soaking time was increased from 4 to 6.75 hrs. The efficiency of acetic acid was much lower than the other two acids. Acetic acid will require much longer soaking times.

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Delayed-Release Acid System for Cleanup of Al Khalij Horizontal Openhole Drains

Cited by 36 publications

References 9 publications

Uranium Wells: The Proper Selection of Drilling Mud and Completion Fluid Has Changed All the Rules of the Game

Uranium Wells: The Proper Selection of Drilling Mud and Completion Fluid Has Changed All the Rules of the Game

Characteristics and Removal of Filter Cake Formed by Formate-Based Drilling Mud

Evaluation of In-Situ Generated Acids for Filter-Cake Cleanup

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