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Hangseok Choi - One of the best experts on this subject based on the ideXlab platform.
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slug test analysis in vertical cutoff walls with consideration of Filter Cake
Journal of Geotechnical and Geoenvironmental Engineering, 2011Co-Authors: The-bao Nguyen, Hangseok ChoiAbstract:In constructing a vertical cutoff wall, bentonite-water slurry is frequently used to maintain the stability of sidewalls during excavation before backfilling the trench with less permeable materials to complete the cutoff wall construction. This procedure leads to a thin but relatively impermeable layer, called a Filter Cake, on the excavation surface. The aim of this paper is to examine the effect of a Filter Cake on evaluating hydraulic conductivity of the cutoff wall backfill through a slug test analysis with the aid of the verified numerical program, Slug_3D. As an upper bound solution for evaluation of the hydraulic conductivity of the cutoff wall backfill, no-flux boundary conditions for the boundaries of cutoff walls are imposed to consider the effect of Filter Cakes. The type-curve method and modified line-fitting method are employed to reanalyze the case of EMCON/OWT, Inc., as an example. The previous analysis, without consideration of a Filter Cake, is compared with the current results that cons...
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Modification of the Bouwer and Rice method to a cutoff wall with a Filter Cake.
Ground Water, 2010Co-Authors: The-bao Nguyen, Chul-ho Lee, Se-won Kim, Hangseok ChoiAbstract:The Bouwer and Rice method is a line-fitting method used to estimate the hydraulic conductivity of an aquifer by means of a slug test. When considering a relatively impermeable layer, called a Filter Cake, which may form at the interface between a cutoff wall and the natural soil formation, the assumptions of the Bouwer and Rice method are violated. A modification of the Bouwer and Rice method is proposed that incorporates the concept of a flow net, whereby the geometry of the cutoff wall and Filter Cake is effectively considered in estimating the hydraulic conductivity of a vertical cutoff wall.
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Hydraulic Conductivity Evaluation of Vertical Cutoff Walls Bearing Filter Cake From Slug Test Analysis
Advances in Environmental Geotechnics, 2010Co-Authors: The-bao Nguyen, Chul-ho Lee, Yonghoon Ahn, Hangseok ChoiAbstract:The hydraulic conductivity of a vertical cutoff wall can be estimated through a slug test analysis. A Filter Cake is a thin and impervious layer formed on the interface between the vertical cutoff wall and the natural soil formation. The conventional line-fitting methods for a slug test analysis have never considered the presence of the Filter Cake. Therefore, results of a slug test analysis using the line-fitting methods for the vertical cutoff wall is believed to be inaccurate due to the effect of the Filter Cake. In this study, the hydraulic conductivity of the Filter Cake was evaluated using a modified fluid loss test. The result of the test indicated that a very low hydraulic conductivity is an important characteristic of the Filter Cake. The slug test analysis with the consideration of the Filter Cake in the line-fitting method was then employed to estimate the hydraulic conductivity of the cutoff wall in a case study. Result of the case study proves the significance of the Filter Cake in the estimation of the hydraulic conductivity of a vertical cutoff wall through a slug test.
Mohamed Mahmoud - One of the best experts on this subject based on the ideXlab platform.
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Self-destructive barite Filter Cake in water-based and oil-based drilling fluids
Journal of Petroleum Science and Engineering, 2021Co-Authors: Zeeshan Tariq, Mohamed Mahmoud, Muhammad Shahzad Kamal, Olalekan S. Alade, Ayman Al-nakhliAbstract:Abstract The complete removal of Filter Cake containing barium sulfate is a challenging and difficult task because of the involvement of various issues such as incompatibility and insolubility. Conventional Filter Cake removal techniques include the use of chelating agents, which are ineffective in completely removing the barite Filter Cakes. Barite is completely insoluble in water as well as in various acids, such as acetic acid, lactic acid, hydrochloric acid, and formic acid. In this study, a novel method is introduced to remove the barium sulfate Filter Cake by introducing a new formulation of both oil-based and water-based drilling fluids. The new formulation can prevent fluid loss as well as self-destruct the barium sulfate Filter Cake, which can be formed with oil-based and water-based drilling fluids. The new formulation is comprised of encapsulated thermochemical fluids in addition to the conventional drilling fluids additives. These thermochemical fluids can cause a strong exothermic reaction that can significantly increase the surrounding temperature and pressure. The generated heat and pressure can dissolve or dislodge the Filter Cake formed with drilling fluid. The laboratory experimental results showed that the new formulation could completely remove the Filter Cake in a single stage within 48 h. In addition to that, the new formulation resulted in the creation of micro-fractures, which can enhance the flowback and help in well cleanup process after drilling. The new formulation can be used as a promising formula to remove the Filter Cake before cementing operation.
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Complex barite Filter Cake removal using in-situ generated acids by thermochemicals
Scientific Reports, 2020Co-Authors: Badr S. Bageri, Mohamed Mahmoud, Ibrahim Gomaa, Shirish Patil, Ayman Al-nakhliAbstract:In sandstone formations, the quartz particles integrate with drilling fluid solids and become part of the Filter Cake structure. As a result, the dissolution rate of the Filter Cake diminishes and reduces the removal efficiency. This paper presents a novel solution to overcome the challenges that restricts the Filter Cake removal process such as the presence of the quartz layer and the polymer coat. A multi-stage method for removing the Filter Cake from a wellbore is presented. The composition of the new formulation is; ammonium fluoride (NH_4F), with a strong oxidizer, such as sodium bromate (NaBrO_3) causes an exothermic reaction in the first stage, thereby removing the quartz layer and polymer coat in the Filter Cake by the in-situ generated HF acid. During the second stage for the barite-based Filter Cake, chelating agents combined with convertor catalysts were used to dissolve the barite. Solubility experiments were conducted to evaluate the efficiency at each stage in the Filter Cake removal process at 300 ºF and 500 psi. The experimental results showed that the formulation consisting of ammonium fluoride (NH_4F), with a strong oxidizer (sodium bromate,NaBrO_3), combined with exothermic reaction was able to generate HF in-situ, which in turn dissolved the quartz mineral and remove the polymer from the Filter Cake.
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effect of arenite calcareous argillaceous and ferruginous sandstone cuttings on Filter Cake and drilling fluid properties in horizontal wells
Geofluids, 2019Co-Authors: Badr S. Bageri, Mohamed Mahmoud, Shirish Patil, Mohammed Benaafi, Abdelmjeed Mohamed, Salaheldin ElkatatnyAbstract:Fine, small-size, drilled cuttings, if not properly separated using mud conditioning equipment at the surface, are circulated with the drilling fluid from the surface to the bottom hole. These drilled cuttings have a significant effect on the drilling fluid properties and Filter Cake structure. During drilling long lateral sandstone formations, different cuttings with varied properties will be generated due to sandstone formations being heterogeneous and having different mineralogical compositions. Thus, the impact of these cuttings on the drilling fluid and Filter Cake properties will be different based on their mineralogy. In this paper, the effect of different sandstone formation cuttings, including arenite (quartz rich), calcareous (calcite rich), argillaceous (clay rich), and ferruginous (iron rich) sandstones, on the Filter Cake and drilling fluid properties was investigated. Cuttings of the mentioned sandstone formations were mixed with the drilling fluid to address the effect of these minerals on the Filter Cake thickness, porosity, and permeability. In addition, the effect of different sandstone formation cuttings on drilling fluid density and rheology, apparent viscosity (AV), plastic viscosity PV), and yield point (YP) was investigated. High-pressure high-temperature (HPHT) fluid loss test was conducted to form the Filter Cake. The core sample’s petrophysical properties were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques and scanning electron microscopy (SEM). The results of this work indicated that all cutting types increased the rheological properties when added to the drilling fluid at the same loadings but the argillaceous sandstone (clay rich) has a dominant effect compared to the other types because the higher clay content enhanced the rheology. From the Filter Cake point of view, the ferruginous sandstone improved the Filter Cake sealing properties and reduced its thickness, while the argillaceous cuttings degraded the Filter Cake porosity and permeability and allowed the finer cuttings to penetrate deeply in the Filter medium.
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investigating the compatibility of enzyme with chelating agents for calcium carbonate Filter Cake removal
Arabian Journal for Science and Engineering, 2018Co-Authors: Salaheldin Elkatatny, Mohamed MahmoudAbstract:Removal of water-based Filter Cake formed during drilling and hydraulic fracturing operations is a difficult task. Conventional acids, such as hydrochloric acid, organic acid, or a mixture of these acids, can be used to remove the Filter Cake. The common issues of these acids are rapid and uncontrolled reaction rate and corrosion to well tubulars, especially in horizontal and deep wells. Chelating agents were introduced in the oil industry to solve the problems associated with the conventional acids. Up to the authors’ knowledge, the reaction of chelating agents with starch, which is a major component of the Filter Cake, was not investigated in the literature. The objectives of this study are to (1) assess the reaction of starch with different chelating agents, namely ethylenediaminetetraacetic acid (EDTA), glutamic acid diacetic acid (GLDA), and diethylene triamine penta-acetic acid (DTPA), at different conditions of pH and temperature, (2) evaluate the compatibility of chelating agents with enzyme [high thermally stable $$\upalpha $$ -amylase enzymes (HTA)], (3) assess the reaction of enzyme with starch and xanthan gum, and (4) design the best scenario for calcium carbonate Filter Cake removal. The obtained results showed that EDTA (20 wt%, pH 7, and 12), DTPA (20 wt%, pH 7, and 12), and GLDA (20 wt%, pH 4, 7, and 12) were not able to break the starch after hot rolling for different time periods at $$200\,{^{\circ }}\hbox {F}$$ . Different chelating agents were found to be incompatible with $$\upalpha $$ -amylase enzyme (HTA enzyme that should be used to remove the starch). The two-stage scenario was found to be the best practice to remove the calcium carbonate Filter Cake in 22 h with 100% removal efficiency and 100% retained permeability. Computer tomography confirmed that external and internal Filter Cake was completely removed, and no formation damage was existing.
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single stage Filter Cake removal of barite weighted water based drilling fluid
Journal of Petroleum Science and Engineering, 2017Co-Authors: Badr Salem Ba Geri, Salaheldin Elkatatny, Mohamed Mahmoud, Abdulazeez Abdulraheem, Saleh H Almutairi, Reyad ShawabkehAbstract:Abstract The removal of barite Filter Cake is a challenging problem because the conventional Filter Cake removal treatments that use hydrochloric acid (HCl) or chelating agents were ineffective in dissolving barite containing Filter Cakes. Barite, or barium sulfate, is insoluble in water and acids such as HCl, formic, citric, and acetic acids. Also barite has very low solubility in chelating agents such as Ethylene diamine tetra acetic acid (EDTA) and Diethylene triamine penta acetic acid (DTPA). The present study focuses on developing new formulation to remove the barite Filter Cake. The removal formulation consists of chelating agents such as Diethylene Triamine Penta acetic Acid (DTPA), converting agent or catalyst, and polymer breaker (Enzyme). Solubility tests of industrial barite and solids collected from de-sanders during well flow back were conducted to develop barite removing solvent. Actual barite drilling fluid samples were collected from the field during drilling a high pressure high temperature deep gas well. The performance of the designed formulation was examined to remove the Filter Cake formed by real drilling fluid samples collected during drilling operations using High Pressure High Temperature cell (HPHT). Based on the result of this work the Filter Cake removing formulation dissolved more than 90% of the Filter Cake formed by real barite drilling fluid in a single stage within 24 h. The removal formulation consists of high pH potassium base DTPA of 20 wt% concentration, enzyme as a polymer degrading agent, and one of the following converting/catalytic agents (potassium carbonate, potassium formate, or potassium chloride). The use of converting agents increased the barite solubility from 67–95%.
Salaheldin Elkatatny - One of the best experts on this subject based on the ideXlab platform.
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effect of arenite calcareous argillaceous and ferruginous sandstone cuttings on Filter Cake and drilling fluid properties in horizontal wells
Geofluids, 2019Co-Authors: Badr S. Bageri, Mohamed Mahmoud, Shirish Patil, Mohammed Benaafi, Abdelmjeed Mohamed, Salaheldin ElkatatnyAbstract:Fine, small-size, drilled cuttings, if not properly separated using mud conditioning equipment at the surface, are circulated with the drilling fluid from the surface to the bottom hole. These drilled cuttings have a significant effect on the drilling fluid properties and Filter Cake structure. During drilling long lateral sandstone formations, different cuttings with varied properties will be generated due to sandstone formations being heterogeneous and having different mineralogical compositions. Thus, the impact of these cuttings on the drilling fluid and Filter Cake properties will be different based on their mineralogy. In this paper, the effect of different sandstone formation cuttings, including arenite (quartz rich), calcareous (calcite rich), argillaceous (clay rich), and ferruginous (iron rich) sandstones, on the Filter Cake and drilling fluid properties was investigated. Cuttings of the mentioned sandstone formations were mixed with the drilling fluid to address the effect of these minerals on the Filter Cake thickness, porosity, and permeability. In addition, the effect of different sandstone formation cuttings on drilling fluid density and rheology, apparent viscosity (AV), plastic viscosity PV), and yield point (YP) was investigated. High-pressure high-temperature (HPHT) fluid loss test was conducted to form the Filter Cake. The core sample’s petrophysical properties were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) techniques and scanning electron microscopy (SEM). The results of this work indicated that all cutting types increased the rheological properties when added to the drilling fluid at the same loadings but the argillaceous sandstone (clay rich) has a dominant effect compared to the other types because the higher clay content enhanced the rheology. From the Filter Cake point of view, the ferruginous sandstone improved the Filter Cake sealing properties and reduced its thickness, while the argillaceous cuttings degraded the Filter Cake porosity and permeability and allowed the finer cuttings to penetrate deeply in the Filter medium.
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investigating the compatibility of enzyme with chelating agents for calcium carbonate Filter Cake removal
Arabian Journal for Science and Engineering, 2018Co-Authors: Salaheldin Elkatatny, Mohamed MahmoudAbstract:Removal of water-based Filter Cake formed during drilling and hydraulic fracturing operations is a difficult task. Conventional acids, such as hydrochloric acid, organic acid, or a mixture of these acids, can be used to remove the Filter Cake. The common issues of these acids are rapid and uncontrolled reaction rate and corrosion to well tubulars, especially in horizontal and deep wells. Chelating agents were introduced in the oil industry to solve the problems associated with the conventional acids. Up to the authors’ knowledge, the reaction of chelating agents with starch, which is a major component of the Filter Cake, was not investigated in the literature. The objectives of this study are to (1) assess the reaction of starch with different chelating agents, namely ethylenediaminetetraacetic acid (EDTA), glutamic acid diacetic acid (GLDA), and diethylene triamine penta-acetic acid (DTPA), at different conditions of pH and temperature, (2) evaluate the compatibility of chelating agents with enzyme [high thermally stable $$\upalpha $$ -amylase enzymes (HTA)], (3) assess the reaction of enzyme with starch and xanthan gum, and (4) design the best scenario for calcium carbonate Filter Cake removal. The obtained results showed that EDTA (20 wt%, pH 7, and 12), DTPA (20 wt%, pH 7, and 12), and GLDA (20 wt%, pH 4, 7, and 12) were not able to break the starch after hot rolling for different time periods at $$200\,{^{\circ }}\hbox {F}$$ . Different chelating agents were found to be incompatible with $$\upalpha $$ -amylase enzyme (HTA enzyme that should be used to remove the starch). The two-stage scenario was found to be the best practice to remove the calcium carbonate Filter Cake in 22 h with 100% removal efficiency and 100% retained permeability. Computer tomography confirmed that external and internal Filter Cake was completely removed, and no formation damage was existing.
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single stage Filter Cake removal of barite weighted water based drilling fluid
Journal of Petroleum Science and Engineering, 2017Co-Authors: Badr Salem Ba Geri, Salaheldin Elkatatny, Mohamed Mahmoud, Abdulazeez Abdulraheem, Saleh H Almutairi, Reyad ShawabkehAbstract:Abstract The removal of barite Filter Cake is a challenging problem because the conventional Filter Cake removal treatments that use hydrochloric acid (HCl) or chelating agents were ineffective in dissolving barite containing Filter Cakes. Barite, or barium sulfate, is insoluble in water and acids such as HCl, formic, citric, and acetic acids. Also barite has very low solubility in chelating agents such as Ethylene diamine tetra acetic acid (EDTA) and Diethylene triamine penta acetic acid (DTPA). The present study focuses on developing new formulation to remove the barite Filter Cake. The removal formulation consists of chelating agents such as Diethylene Triamine Penta acetic Acid (DTPA), converting agent or catalyst, and polymer breaker (Enzyme). Solubility tests of industrial barite and solids collected from de-sanders during well flow back were conducted to develop barite removing solvent. Actual barite drilling fluid samples were collected from the field during drilling a high pressure high temperature deep gas well. The performance of the designed formulation was examined to remove the Filter Cake formed by real drilling fluid samples collected during drilling operations using High Pressure High Temperature cell (HPHT). Based on the result of this work the Filter Cake removing formulation dissolved more than 90% of the Filter Cake formed by real barite drilling fluid in a single stage within 24 h. The removal formulation consists of high pH potassium base DTPA of 20 wt% concentration, enzyme as a polymer degrading agent, and one of the following converting/catalytic agents (potassium carbonate, potassium formate, or potassium chloride). The use of converting agents increased the barite solubility from 67–95%.
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Removal Efficiency of Water-based Drill-in Fluid Filter Cake Using Polylactic Acid (SPE 154192)
2012Co-Authors: Salaheldin Elkatatny, Hisham A. Nasr-el-dinAbstract:Water-based drilling fluids consist of xanthan gum, starch, sized calcium carbonate and salt particles to increase mud density was used to drill horizontal wells. Available chemical methods of removing Filter Cake like mineral acids, esters, oxidizers, and chelating agents are limited at certain conditions. A drilling fluid was designed based on calcium carbonate particles and an ester of lactic acid. The objective of the latter is to remove calcium carbonate once the drilling operation is complete and there is a need to remove the Filter Cake. Extensive lab work was done to; 1) determine thermal stability of the drilling fluid (70-72 pcf) for 24 hrs, 2) characterize the Filter Cake using a computer tomography, 3) assess potential formation damage for different rock types (limestone and sandstone) using a modified HPHT Filter press, and 4) determine the removal efficiency of the Filter Cake and the return permeability. The results obtained showed that the drilling fluid has stable rheological properties up to 300oF over 24 hrs. CT scan showed that the Filter Cake contained two layers, one layer closed to the rock surface, which contained a mixture of calcium carbonate and acid-precursor and one layer closed to the drilling fluid that contained a mixture of XC-polymer and starch. The polymer layer was removed by using 10% solution of alpha amylase. The rest of the Filter Cake was removed by lactic acid that was produced from the hydrolysis of the ester. The removal efficiency of the Filter Cake was nearly 80% and the return permeability was about 100%. The decrease in CT number of the core after the removal process indicated that the Filter Cake was completely removed. This paper will discuss the development of this new drilling fluid and will give recommendations for field applications.
Abdulazeez Abdulraheem - One of the best experts on this subject based on the ideXlab platform.
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single stage Filter Cake removal of barite weighted water based drilling fluid
Journal of Petroleum Science and Engineering, 2017Co-Authors: Badr Salem Ba Geri, Salaheldin Elkatatny, Mohamed Mahmoud, Abdulazeez Abdulraheem, Saleh H Almutairi, Reyad ShawabkehAbstract:Abstract The removal of barite Filter Cake is a challenging problem because the conventional Filter Cake removal treatments that use hydrochloric acid (HCl) or chelating agents were ineffective in dissolving barite containing Filter Cakes. Barite, or barium sulfate, is insoluble in water and acids such as HCl, formic, citric, and acetic acids. Also barite has very low solubility in chelating agents such as Ethylene diamine tetra acetic acid (EDTA) and Diethylene triamine penta acetic acid (DTPA). The present study focuses on developing new formulation to remove the barite Filter Cake. The removal formulation consists of chelating agents such as Diethylene Triamine Penta acetic Acid (DTPA), converting agent or catalyst, and polymer breaker (Enzyme). Solubility tests of industrial barite and solids collected from de-sanders during well flow back were conducted to develop barite removing solvent. Actual barite drilling fluid samples were collected from the field during drilling a high pressure high temperature deep gas well. The performance of the designed formulation was examined to remove the Filter Cake formed by real drilling fluid samples collected during drilling operations using High Pressure High Temperature cell (HPHT). Based on the result of this work the Filter Cake removing formulation dissolved more than 90% of the Filter Cake formed by real barite drilling fluid in a single stage within 24 h. The removal formulation consists of high pH potassium base DTPA of 20 wt% concentration, enzyme as a polymer degrading agent, and one of the following converting/catalytic agents (potassium carbonate, potassium formate, or potassium chloride). The use of converting agents increased the barite solubility from 67–95%.
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Effect of Sand Content on the Filter Cake Properties and Removal During Drilling Maximum Reservoir Contact Wells in Sandstone Reservoir
Journal of Energy Resources Technology-transactions of The Asme, 2015Co-Authors: Badr Salem Ba Geri, Mohamed Mahmoud, Saleh H. Al-mutairi, Abdulazeez AbdulraheemAbstract:The drilling mud program contains many tests such as filtration rate and Filter Cake properties to select the proper drilling fluid additives that yield the standard ranges of the viscosity, filtration rate, etc. However, the physical and chemical changes in the mud composition during the mud circulating will cause changes to the Filter Cake properties. The changes in the Filter Cake properties should be considered in the mud design program to prevent the problems associated with the change in the drilling fluid properties. For long horizontal wellbores penetrating plastic formations, the two sources of solids in Filter Cake are drilling chemical additives and formation cuttings (sand particles in the case of sandstone reservoir). This study focuses on the effect of introducing sand particles from the drilled—formations on the Filter Cake properties. Real drilling fluid samples from the field were collected at different location during drilling a 3600 ft of the horizontal section of a sandstone formation. Calcium Carbonate (CaCO3) was used as weighting material in this filed. The drilling fluid samples were collected at two different points: the flow line coming from the well after shale shaker and the flow line going to the well to verify the effect of separation stages on Filter Cake properties. The primary drilling fluid properties of the collected samples were measured such as density and rheological parameters. High pressure high temperature (HPHT) Filter press was used to perform the filtration and Filter Cake experiments at 300 psi differential pressure and room temperature (25 °C). The mineralogy of the external Filter Cake formed by fluid loss cell is determined using SEM (scanning electron microscopy) and XRD (X-ray diffraction). Finally, solubility test was conducted to evaluate the effect of sand particles on Filter Cake removal (containing Calcium Carbonate as weighting material) using chelating agent: glutamic diacetic acid (GLDA) at pH 4. The results showed that for long horizontal sections, the effect of introducing sand particles to the composition of the Filter Cake can cause significant change to the properties of Filter Cake such as mineralogy, thickness, porosity, and permeability. For instant the thickness of Filter Cake increased about 40% of its original thickness when drilling sandstone formation in horizontal well due to fine sand particle settling. The Filter Cake porosity and permeability increment in the first 2000 ft part of the horizontal section was observed clearly due to the irregular shape of the drilling particles. However for the points after the first 2000 ft of horizontal lateral, the porosity and permeability almost remained constant. Increasing the sand content up to 20% degrade the dissolution rate of calcium carbonate in the GLDA (pH = 3.8) to 80% instead of 100%.
The-bao Nguyen - One of the best experts on this subject based on the ideXlab platform.
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slug test analysis in vertical cutoff walls with consideration of Filter Cake
Journal of Geotechnical and Geoenvironmental Engineering, 2011Co-Authors: The-bao Nguyen, Hangseok ChoiAbstract:In constructing a vertical cutoff wall, bentonite-water slurry is frequently used to maintain the stability of sidewalls during excavation before backfilling the trench with less permeable materials to complete the cutoff wall construction. This procedure leads to a thin but relatively impermeable layer, called a Filter Cake, on the excavation surface. The aim of this paper is to examine the effect of a Filter Cake on evaluating hydraulic conductivity of the cutoff wall backfill through a slug test analysis with the aid of the verified numerical program, Slug_3D. As an upper bound solution for evaluation of the hydraulic conductivity of the cutoff wall backfill, no-flux boundary conditions for the boundaries of cutoff walls are imposed to consider the effect of Filter Cakes. The type-curve method and modified line-fitting method are employed to reanalyze the case of EMCON/OWT, Inc., as an example. The previous analysis, without consideration of a Filter Cake, is compared with the current results that cons...
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Modification of the Bouwer and Rice method to a cutoff wall with a Filter Cake.
Ground Water, 2010Co-Authors: The-bao Nguyen, Chul-ho Lee, Se-won Kim, Hangseok ChoiAbstract:The Bouwer and Rice method is a line-fitting method used to estimate the hydraulic conductivity of an aquifer by means of a slug test. When considering a relatively impermeable layer, called a Filter Cake, which may form at the interface between a cutoff wall and the natural soil formation, the assumptions of the Bouwer and Rice method are violated. A modification of the Bouwer and Rice method is proposed that incorporates the concept of a flow net, whereby the geometry of the cutoff wall and Filter Cake is effectively considered in estimating the hydraulic conductivity of a vertical cutoff wall.
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Hydraulic Conductivity Evaluation of Vertical Cutoff Walls Bearing Filter Cake From Slug Test Analysis
Advances in Environmental Geotechnics, 2010Co-Authors: The-bao Nguyen, Chul-ho Lee, Yonghoon Ahn, Hangseok ChoiAbstract:The hydraulic conductivity of a vertical cutoff wall can be estimated through a slug test analysis. A Filter Cake is a thin and impervious layer formed on the interface between the vertical cutoff wall and the natural soil formation. The conventional line-fitting methods for a slug test analysis have never considered the presence of the Filter Cake. Therefore, results of a slug test analysis using the line-fitting methods for the vertical cutoff wall is believed to be inaccurate due to the effect of the Filter Cake. In this study, the hydraulic conductivity of the Filter Cake was evaluated using a modified fluid loss test. The result of the test indicated that a very low hydraulic conductivity is an important characteristic of the Filter Cake. The slug test analysis with the consideration of the Filter Cake in the line-fitting method was then employed to estimate the hydraulic conductivity of the cutoff wall in a case study. Result of the case study proves the significance of the Filter Cake in the estimation of the hydraulic conductivity of a vertical cutoff wall through a slug test.