Slurry Design Research Articles

An Alkaline Slurry Design for Co-Cu CMP Systems Evaluated in the Tribo-Electrochemical Approach

The sub-14 nm technology nodes of integrated circuits require metal components of ultrathin linewidths. The chemical mechanical planarization (CMP) protocols needed to process such structures are associated with several challenges, one of which is to design/screen slurry formulations required to address both the scaling and the nontraditional metal chemistries of these structures. Laboratory scale tribo-electrochemical techniques serve as a cost-effective yet comprehensive means to aid these tasks, and the present work focuses on further quantifying this approach with an alkaline slurry formulation designed to planarize Co diffusion barriers for Cu lines. The CMP strategy uses controlled corrosion in a (potentially abrasive-free) slurry of potassium acetate, hydrogen peroxide, and benzotriazole. The tribo-electrochemical experiments involve open circuit potential transients, current interruption, and potentiodynamic polarization. Material removal rates, normalized with respect to the polisher parameters are analyzed as specific wear rates to quantitatively probe the chemical aspects of CMP. The slurry functions necessary to control galvanic corrosion and CMP selectivity of Co are investigated. The necessity for incorporating tribo-control in these measurements is demonstrated by showing how the results obtained with stationary metal samples could result in misleading conclusions about the galvanic corrosion rates.

Simulation of the Melting Process of Ice Slurry for Energy Storage Using a Two-Fluid Lattice Boltzmann Method

Abstract: Ice slurry can be used as the thermal storage media in latent cool storage systems for both residential and commercial buildings. This paper presents the investigation of the phase change characteristics of the ice slurry using a two-fluid Lattice Boltzmann Method (TFLBM). The melting and migration processes of the ice slurry are simulated by improving the equilibrium distribution function and matching the relevant parameters such as the kinetic viscosity of ice particle cluster and cross-collision coefficient. The sensitivity analysis of the ice slurry viscosity and cross-collision coefficient are achieved through six numerical experiments, and the ice melting in the internal-melt ice-on-coil thermal storage device is then calculated. The results could be potentially used to guide the design of the ice slurry for cooling both residential and commercial buildings.

Tantalum carbide coating via wet powder process: From slurry design to practical process tests

TaC coatings were deposited on graphite substrates via wet powder forming and sintering to potentially achieve both a highly reliable and low-cost process. Non-aqueous solvent mixtures of TaC slurries were optimized through characterization of raw materials and a novel design guide based on Hansen solubility parameters. The optimized TaC slurries enabled the formation of high-quality TaC powder compact films with ultrahigh powder packing densities of ≥70% (ca. 85% at maximum), which contributed to prevent defect formation in the TaC coatings after sintering. The TaC-coated components were tested in practical high-temperature processes, such as AlN and SiC bulk single crystal growth processes, and a SiC device fabrication process, which confirmed sufficiently low-levels of impurity incorporation and surface contamination from the TaC layers. The novel TaC-coated graphite components will contribute to higher quality and lower cost for bulk crystal growth, device fabrication, and epitaxial film growth processes of group-III nitrides and SiC.

Portland cement solutions for ultra-high temperature wellbore applications

Designing highly stable and low permeability high-strength oil well cement above 500 °F (>260 °C) is extremely difficult because the Portland cement undergoes strength retrogression starting at 230 °F (110 °C). Thus, fine crystalline silica stabilizer is required in the cement slurry design when cured until 400 °F (204.4 °C) to prevent this problem. However, the optimum particle size and the right practical dosage of silica in the cement slurry have not been clearly determined and studied for cement that will be subjected at such extremely high temperature (>500 °F), condition applicable for many ultra-deep geothermal and steam injection wells. Due to extreme heating conditions and tedious experimentation, there are only few published studies to date toward understanding the behavior of Portland cement used at that exceedingly high temperature; and thus, making the initial cement design highly challenging. Based on thorough experimental study, this paper presents new understanding and provides proper guidance to designing highly stable non-retrogressing and low steady permeability oil well cement for ultra-high temperature use. Moreover, this research carefully investigates the effect of the particle size of crystalline silica to the compressive strength, porosity and permeability of the cured cement. Finally, the substitution of crystalline silica with amorphous silica material in the ultra-high temperature cement is also exploited. Supplementary powder X-ray diffraction measurement identifies high temperature stable crystal phase Xonotlite (Ca6Si6O17(OH)2) in the silica-stabilized Portland cement. However, based from these current experimental results, it is observed that formation of Xonotlite crystal phase does not completely guarantee the longer term mechanical integrity of the cement sheath at ultra-high temperature, especially when the mixture contains amorphous-type silica in the blend.

Design and Application of Removable Plugging Slurry for Fractured Carbonate Reservoir

To meet the requirements of leakage stopping and reservoir protection at the same time in fractured formation, the removable plugging slurries with high temperature tolerance were designed, evaluated and applied in the field successfully. Analysis shows that the fibre materials can deposit onto crack surface, bridge and seal fractures quickly and the selected particles can bridge in throat near wellbore. The comprehensive grading of filling particles was determined from the point of view of gradient filling. The designed plugging slurries KJD155 and KJD200 with higher total dissolution rates sealed 1 mm, 2 mm, 3 mm, and 4 mm crack blocks effectively at room temperature and high temperature (KJD155 at 155 °C; KJD200 at 200 °C) respectively. Their pressure bearing ability of them was up to 5 MPa under bottom hole conditions, which was beneficial to the next operation. Field application of the designed plugging slurries was carried out successfully and showed that they were removable and did smaller damage to reservoir.

Oil Well Cement Additives: A Review of the Common Types

Abstract Additives play significant role in oil and gas well cementing operations. There are varieties of cement additives that have been developed to allow the use of Portland cement in many different oil and gas well operations. In an attempt to formulate the appropriate cement slurry for any cementing job, the right additive must selected and the right quantity must be added. Additives have different functions and are broadly classified as accelerator, retarders, extenders, fluid loss agents, dispersants and many more. Each of the broad classification has different categories of additives that have been developed to perform almost the same function during cement slurry design. However, there some additives under each major type that are commonly used in cement slurry design for oil and gas well cementing operations. This paper reviews the broad classification of oil well additives giving emphasis to the commonly used additives during oil and gas well cementing operations.

Cement Evaluation—A Risky Business

Summary Cement evaluation is often limited to running a cement-bond log (CBL) and making some attempt to interpret the results and determine whether there is isolation in the wellbore. Often, that interpretation is made in isolation with little or no information on what occurred during the drilling and cementing of the well, or the cement systems used. Evaluating cement in older wells where the drilling report states “ran casing, cemented same” can be particularly challenging. Cement evaluation is much more than just a CBL. Understanding the objectives of the cement job, the design limitations imposed by those objectives, and the resulting slurry and job designs are integral parts of cement evaluation. Often, the selection of a specialty cement system to meet specific job objectives can dictate how one can evaluate the cement. To properly evaluate a cement sheath, knowledge of the cement job, slurry designs, and the limitations of the evaluation technique. To attempt to perform a cement evaluation that is based solely on the log output from a CBL, or any log, invites considerable error and bias into the resulting interpretation. This paper reviews various methods of cement evaluation—from job data, casing- and formation-pressure testing through sonic and ultrasonic logging. The assumptions associated with each technique are outlined, and the discussion includes some of the limitations of the various techniques, along with cautions on how misinterpretation of the results can lead to assumptions of cement integrity that may not be appropriate. The impact of new specialty cement designs, which incorporate high concentrations of inert materials to give the set cement unique properties, is discussed. The ability of specific logging methods to evaluate the presence of these slurries is presented. Data on selected specialty cement systems in which conventional ultrasonic cement-analyzer-strength data are not representative of the crush strength of the cement caused by the incorporation of specialty materials are included. Both overview of cement evaluation and a risk-based discussion of the technique that may be most appropriate on the basis of the cementing objectives are presented. Methods of reducing risk uncertainty in cement evaluation are discussed along with the “validity” of the various data sets available to the engineer to perform a proper cement evaluation on the well. Understanding the objectives of the cement job sets the boundary conditions for the designs, and from those designs, one can determine the ability to evaluate the resulting cement placement and well isolation. Setting the evaluation methodology and understanding the type of information required to apply that methodology can improve the quality of the evaluation.

Fe2O3 nanoparticles improve the physical properties of heavy-weight wellbore cements: A laboratory study

The application of nanomaterials to solve problems in wellbore cementing has been investigated in recent years by several research groups in the petroleum industry. This study includes the laboratory examination of the effect of Fe2O3 nanoparticles as a weighting agent on the physical properties of a heavy-weight wellbore cement. In the research process a candidate well is selected and the properties of the used cement slurry in a problematic section of the well are tested in the laboratory. Then Fe2O3 nanoparticles are added as a weighting agent to partially replace the Hidense and the improvements in the cement slurry and stone properties are studied. This article discusses the problems associated with the conventional heavy-weight wellbore cement used in the candidate well and gives the detail of the improvements in cement properties obtained by adding Fe2O3 nanoparticles to cement slurry formulation as a weighting agent. These properties include cement slurry rheological properties, free water, fluid loss, thickening time, cement stone elastic properties and compressive strength. The nano additive increases the yield point and plastic viscosity and decreases the free water and fluid loss of a cement slurry. In addition, cement stone compressive strength increases, however, there is an optimum concentration of nano additive at which the maximum compressive strength is reached. Moreover, elastic properties of the cement stone are improved and higher values for the Young's modulus and Poisson's ratio are achieved. The results of this study can be used to optimize the cement slurry design in any given set of conditions. The modified cement using this approach, is applicable in high pressure fluid bearing zones.

Improvement and Control of Cement Slurry Formulation Resistant to the Critical Conditions HPHT

The ambition of the world oil industry is currently directed toward the deepest traps of oil and gas, despite the very high temperatures. The objective of this study is to improve and control a conventional formulation of cement slurry that meets the critical conditions during the cementing of 7" liner on high pressure/high temperature (HPHT) gas well at 5570m depth, located at Hassi Berkine in the southern Algeria. Under the influence of high temperature, the characteristics of the cement slurry changed. We carried out several tests on various samples in order to revise the design by using equivalent substitutions of the additives to obtain a better profile. The use of a new, very powerful, synthetic retarder (SR-31L) instead of liquid, modified sodium lignosulfonate (R-15 L) led us to obtain a significant thickening time but decreased the rheological properties as well as fluid loss and free water. We also provided a gas block by introducing latex-styrene-butadiene with a specific stabilizer (LS-1) in combination with a compatible bonding agent (amorphous silica) in aqueous suspension (BA-58L). The study determined one of the best cement slurry designs practicable on different down-hole applications in HPHT wells.

Using Fatigue-Failure Envelope for Cement-Sheath-Integrity Evaluation

Summary Tensile and shear failures are two common cement-sheath failure criteria. Tensile failure occurs when a stress on the cement surpasses the tensile strength of the cement, and shear failure happens when a stress exceeds the shear strength of the cement. The objective of this study is to introduce a laboratory method that investigates the effects of fatigue (cyclical loading) on the cement sheath. Chances of cement-sheath failure also increase when the application involves high-pressure/high-temperature conditions; therefore, this test setup is rated to 25,000 psi and 450°F. In this method, fatigue-failure cycle and stress magnitude could reveal the extent of the fatigue tolerance of different slurry designs relative to each other. One could program and adjust casing pressure (Pi), pore pressure (PP), temperature, cycle intervals, and ramp rates to conduct a cyclical-loading test automatically. Failures caused by thermal and stress loading may occur as a result of temperature and pressure-induced stresses created by well events such as hydraulic fracturing, cyclic steam injection, steam-assisted gravity drainage, production, completion, or remedial treatments. Thermal and stress cycles could impose a risk to zonal isolation and lead to a delay in hydrocarbon production. Studying such effects could be helpful in developing a better understanding of the cement-sheath-failure threshold and, in fact, could be complementary to mechanical-properties measurement. The cement sheath fails after a certain number of cycles when reaching its fatigue-endurance limit. This research showcases examples in which the fatigue-failure cycles were identified for 1,000-, 2,000-, and 5,000-psi pressure differentials between the pore pressure (exposed to the outside of the sheath) and the casing pressure. For these experiments, the pore pressure and temperature were held constant at 15,000 psi and 330°F whereas the casing pressure varied cyclically between 15,000 and 16,000 psi (Set A), 17,000 psi (Set B), and 20,000 psi (Set C).

The Case of Coal Water Slurry Fuel for Industrial Use in Pakistan

This research presents the case for design and development of Coal Water Slurry (CWS) Plant for industrial use in Pakistan. After exclusive comparison between coal quality quantification for CWS it was found that Darra mines at Pakistan provide best coal for CWS. Highly volatile, A and B Bituminous coal and Sub-Bituminous coal is selected for making CWS because of its low Sulfur contents, Ash contents and high heating value through experimentation. The purpose of this research was to present a complete blue print for the production of coal water slurry fuel in Pakistan. The measured viscosity and heat contents of the tested CWS are of the order 490 mPa-sec and 23.8 KJ/kg, respectively.

The Use of a Novel Spacer and Ultralow-Density Cement System To Control Lost Circulation in Coalbed-Methane Wells

Summary Coalbed methane (CBM) is one of the major clean-burning gas resources. Development and usage of CBM can increase the energy supply, improve coal-mine safety, and protect the global environment. The southern Qinshui basin of China is rich in CBM; it is the first area that obtained good results in the commercial development of CBM in China. However, lost circulation is a common problem during cementing through the fractured coal-seams, known as cleats. These cleats form an interconnected fracture network, and this allows cement-slurry loss to the coal-seams during cementing operations. Cleats are often wide enough to accept cement slurry, not just cement-slurry filtrate. Hence, simply reducing slurry density does not ensure a good cement job. Preventing cement-slurry loss to coal-seams while cementing production casing is a major challenge. To solve the lost-circulation problem across coal formations, an innovative hydrophilic-fiber-based spacer fluid and ultralow-density cement slurries with density of 0.95 to 1.20 g/cm3 have been formulated. Laboratory tests have verified the effectiveness of hydrophilic-fiber-based spacer fluid in plugging these cleats of coal seams. The ultralow-density cement slurries exhibit favorable properties. These test results are confirmed by the good field-application results obtained in southern Qinshui basin. Fourteen CBM wells were successfully cemented with the novel spacer fluid and the ultralow-density cement slurries. The combined application of the hydrophilic-fiber-based spacer fluid and the ultralow-density-cement-slurry system is able to successfully resolve the lost-circulation problem in CBM wells, and provides better zonal isolation as well. This paper provides details about the slurry design and field application, and also presents the cement-bond evaluations that verify the conclusions.

Cement slurry optimization and assessment of additives according to a proposed plan

Wellbore cementing is an essential part of every completion plan. The primary target of a cement job is zonal isolation and avoiding formation fluids to invade the well. Failure of cements in this important task result in disasters, significant financial damages and many more consequences. Good Cement slurry design is the key factor of having a gas resistant cement column. The aim of the study was to optimize slurry formulations following a determined checklist of criteria. The performance of two anti-gas migration and thixotropic agents were also assessed. As the final stage of the slurry optimization plan the results were verified using fluid migration analysis (FMA) test. According to the results, total gas migration flow rate of cement slurry optimized using the presented checklist was recorded as 0.23 ml/min. It was also observed that thixotropic agents improved gel strength profile, filtration control, waiting on cement time (WOC), critical hydration time and cement transition time significantly.

PETROPHYSICAL AND MICROSTRUCTURAL EVALUATION OF THE THERMAL CYCLE LOADING EFFECT ON GEOTHERMAL WELLBORE CEMENTS

Five wellbore cement designs with a range of additives and fibers were subjected to 100 thermal cycles of ΔT ~50°C at 100% relative humidity in salt brine. The experimental results show leaching of portlandite will occur from the cement irrespective of wellbore cement slurry design, which causes the porosity and hydraulic conductivity to increase and the mechanical strength to decrease. Furthermore, the study shows the presence of steel fibers can improve the mechanical properties of the cement sheath under thermal cycle loading conditions; although it would not prevent it from completely degrading as the well ages.

Comparative experimental evaluation of drilling fluid contamination on shear bond strength at wellbore cement interfaces

Wellbore cement has been used to provide well integrity through zonal isolation in oil and gas wells as well as geothermal wells. Failures of wellbore cement result from either or both: inadequate cleaning of the wellbore and inappropriate cement slurry design for a given field/operational application. Inadequate cementing can result in creation of fractures and microannuli, through which produced fluids can migrate to the surface, leading to environmental and economic issues such as sustained casing pressure, contamination of fresh water aquifers and, in some cases, well blowout. To achieve proper cementing, the drilling fluid should be completely displaced by the cement slurry, providing clean interfaces for effective bond. This is, however, hard to achieve in practice, which results in contaminated cement mixture and poor bonds at interfaces. This paper reports findings from the experimental investigation of the impact of drilling fluid contamination on the shear bond strength at the cement-formation and the cement-casing interfaces by testing different levels of contamination as well as contaminations of different nature (physical vs. chemical). Shear bond test and material characterization techniques were used to quantify the effect of drilling fluid contamination on the shear bond strength. The results show that drilling fluid contamination is detrimental to both cement-formation and cement-casing shear bond strength.

Modeling Pore Continuity and Durability of Cementitious Sealing Material

In this paper, results of a numerical study on pore continuity, permeability and durability of cementitious slurries for carbon sequestration projects are presented. The hydration model Hymostruc is used to simulate and visualize 3D virtual microstructures which are used to demonstrate the contribution of capillary pores to the continuity of the capillary pore system embedded in an evolving cementitious microstructure. Once capillary pores are blocked due to ongoing hydration, transport of CO2 species through the microstructure is avoided which may protect the slurry from leakage. Evaluating the pore continuity of the capillary pore system during hydration of the microstructure is therefore indispensable for a robust cementitious sealing material and is the main objective for slurry design. Simulations are conducted on slurries exposed to ambient temperatures of 20 °C, 40 °C, and 60 °C, and a durability outlook regarding the CO2 ingress is given as well. Aggregates and associated interfacial transition zones (ITZs) are introduced in the slurry system that may cause alternative porous path ways through the system. Pore continuity analysis shows the relevance of numerical simulations for assessing the capillary pore structure inside an evolving microstructure in relation to its sealing and durability performance.

The Research of Slurry Foaming of Wet Flue Gas Desulfurization System of Steel Works

This paper focus on the analysis of the slurry foam of the sinter band plant Wet Flue Gas Desulfurization (WFGD) process, and put forward suggestions according to the actual conditions of the Steel Works. The experimenter compared the actual operating parameters of slurry and system design parameter. Then found out the main incentive to form foam on top of the absorber’s slurry tank. This paper analyzed the major constituents of overflow foaming of WFGD system. Analysis results indicated that it is the same composition of byproducts gypsum of WFGD. So the experiment focus on the research of slurry constituents of the absorber. The result of basic data analysis shows that the slurry density of absorber is 1.25Kg/L which exceeds the maximum design value i.e.1.15Kg/L, and the Chloride concentration is 80000mg/L which exceeds the maximum design value i.e. 15000mg/L. The supernatant of slurry is formed of colloidal solution and the solid percentage of supernatant slurry is 10.64% (Weight percentage). Meanwhile the supernatant slurry shows Tyndall phenomenon significantly, and the remaining solution indicators are much higher than the design value. For identification purpose, the experimenter had an experiment about desulfurization slurry and found the relationship among solid content, supernatant concentration, foaming ability and foaming stability. Experimental results show that the foaming ability get strong first and then get weak with the increase of the solid content and the foaming ability get weak gradually with the decrease of the concentration of Mg2+and Cl-. The slurry almost has no foaming when the solid content is less than 10% and the concentration of Mg2+ less than 1000mg/L and the concentration of Cl- less than 20000mg/L.

Evaluación de desempeño de dos diseños de lechadas de cemento para sistemas de recuperación térmica en el Campo Chichimene ubicado en la cuenca de los Llanos Orientales

Se evaluó el desempeño de dos diseños de lechadas de cemento para sistemas de recuperación térmica en el Campo Chichimene, a través de pruebas de laboratorio. Se establecieron rangos de diseño para el proyecto teniendo en cuenta las condiciones de un pozo real perforado en el campo, al igual que los estándares de calidad exigidos por Ecopetrol S.A. para este tipo de proyectos, tanto para propiedades API como para propiedades mecánicas. De acuerdo con los resultados obtenidos, la tecnología B es la que mejor se ajusta a los requerimientos para el proyecto; por lo tanto, es la recomendada para su uso en la cementación de los pozos de éste u otro campo, que tengan condiciones similares al pozo escogido para establecer los rangos de propiedades.

Band application of slurry in orchards using a prototype spreader with an automatic rate controller

A prototype slurry spreader for band application in orchards was designed, constructed, and tested. The spreader comprised several components: 1) 5 m3 tank, 2) distribution device of trailing hoses to reduce ammonia emissions during application, 3) automatic rate controller to apply nitrogen per crop requirements, and 4) low-pressure, wide-section tyres to mitigate soil compaction and sward damage. The slurry tanker design fitted between tree row spacings accounting for tree shape differences. The spreading system consists of two groups of six trailing hoses; each hose group distributes slurry into two 1.0 m wide bands alongside the machine and 0.5 m from tree rows. Operator input of slurry total nitrogen content, determined by onboard hydrometer in the field, and target application rate in the control unit ensured that nitrogen was applied at a constant rate based on metering pump rotational speed as a function of machine forward speed. The rate control system was tested at different application doses and with rapid changes in machine forward speed (range of 3–9 km h−1). The machine responded promptly (<2 s) to forward speed changes, and the spreader evenly distributed slurry in both application bands (Dave < 2.5% on the treated surface). Band application of slurry by the trailing hose device reduced ammonia emissions by 63% compared to the common broadcast application system by splash plate.

CFD simulation of a pilot scale slurry photocatalytic reactor and design of multiple-lamp reactors

The hydrodynamics behaviour and radiation transport occurring inside a pilot-scale slurry photocatalytic reactor (treating real shower water) with large diameter was investigated using computational fluid dynamics (CFD). The multiphase flow system was solved using a granular Eulerian model while the solution of the radiative transport equation (RTE) was solved using the finite volume based discrete ordinate model (DOM). Multiphase simulation showed recirculation zones caused by the high slurry inlet velocity. Due to the rapid attenuation of light occurring radially within the reactor, regions of varying reaction orders exist, i.e., half order reaction close to the lamp and first order reaction further from the lamp, as the incident radiation goes below a certain value. A rate equation relating pollutant degradation to the rate occurring in the half and first order reaction regions (in terms of local volumetric rate of energy absorption – LVREA) was proposed. Using a value of 225Wm−2 as the minimum incident light intensity at which half order reactions take place, a Pearson correlation of 0.88 between simulated and experimental data indicated that the proposed model satisfactorily described the experimental observations. Next, simulations performed with a system of multiple lamps (2 and 4 lamps) at different geometrical arrangements (i.e. with the lamps separated by the distance Xlamp) showed that within the range of catalyst concentration investigated, the maximum potential increases in reaction rate was 56% and 123% when using 2 and 4 lamps (at optimum lamp arrangement) respectively, as compared to using one lamp. The increase in reaction rate occurred due to the maximisation of incident radiation contours at which first order reactions take place. The optimum lamp separation was dependent on the catalyst concentration in the wastewater and decreased with increasing catalyst concentration.