Drilling Fluid Additives Research Articles

A triterpenoid saponin as an environmental friendly and biodegradable clay swelling inhibitor

The drilling industry is motivated to develop high performance clay swelling inhibitors with good biodegradability and low toxicity. In this study, the non-ionic surfactant glycyrrhizin was obtained as Glycyrrhiza glabra root extract (GGRE) as a clay swelling inhibitor. The swelling inhibitive property of the biosurfactant was systematically evaluated through various experiments including mud making, filtration, shale cuttings recovery, sedimentation, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). We compare the performance of our surfactant with a synthetic surfactant (TX-100) and a commonly used clay inhibitor (KCl). Compared to the baseline swelling test without inhibitors, the aqueous solution of GGRE shows much more montmorillonite (Mt) loading capacity and fluid loss, less shale cuttings disintegration, unstable Mt dispersion, larger aggregated Mt particles, and lower Mt mass loss. The inhibitive performance of the GGRE was found to outperform that of the KCl. The results show that TX-100 does not provide inhibition. The compatibility with the drilling fluid formulation was investigated through the rheological and fluid loss analysis. GGRE is found to be compatible with the commercial drilling fluids additives. The inhibition mechanism was also investigated through wettability investigation and FT-IR analysis. The results show that GGRE can strongly reduce the hydrophilicity of Mt. From FT-IR spectra, the interaction between Mt and GGRE is obvious. Our results imply that GGRE possesses good inhibitive characteristic in hindering Mt swelling. The molecule of glycyrrhizin—the main component of GGRE—consists of a hydrophobic triterpenoid backbone, connected by glycosidic bonds to a hydrophilic group. The inhibition mechanism is hypothesized through the formation of a hydrophobic shell on Mt's surfaces; the hydrophilic group of the glycyrrhizin interacts with the oxygen atoms available on Mt's surfaces, while the hydrophobic part orients toward the aqueous phase. The results obtained from this research will be beneficial to enhanced oil recovery studies in Mt-rich formations.

Integrity changes of cement sheath due to contamination by drilling fluid

Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), infrared spectroscopy and x-ray diffraction were used to explore the effects of drilling fluid contamination on the mechanical and porosity–permeability properties of cement stone. The experimental results showed that the mechanical and porosity–permeability properties deteriorated due to contamination by drilling fluid. The deterioration in properties was found to be more serious with an increase in drilling fluid content: for a drilling fluid content of 30%, mechanical properties were reduced by about 50% compared with those of pure cement stone, and porosity and permeability were increased by 7·9% and 0·369 millidarcy (3·6 × 10−12 cm2). SEM, EDS and TGA revealed that chemical incompatibility between drilling fluid additives and cement slurry is the main reason for contamination: the additives contain many functional groups that are not compatible with cement slurry (e.g. carboxylate (–COO−) and amide groups (–CONH2)). These additives easily generate a flocculation mechanism when in contact with cement slurry. They are adsorbed onto the surfaces of cement grains, thus coating the cement particles, reducing the hydration reaction rate and destroying development of the cement stone microstructure, leading to a reduction in strength and an increase in porosity and permeability.

Investigation of melamine derived quaternary as ammonium salt potential shale inhibitor

Melamine, sodium chloroacetate and sodium hydroxide were used as raw materials to synthesize a kind of neutral quaternary ammonium salt (NQAS) as potential clay swelling inhibitor and water-based drilling fluid additive, and the reaction conditions were screened based on the linear expansion rate of bentonite. The inhibitive properties of NQASs were investigated by various methods, including montmorillonite (MMT) linear expansion test, mud ball immersing test, particle distribution measurement, thermogravimetric analysis and scanning electron microscopy etc. The results indicate that NQAS can inhibit expansion and dispersion of clay in water effectively. At the same condition, the bentonite linear expansion rate in NQAS-6 solution is much lower than those of others, and the hydration expansion degree of the mud ball in 0.5% NQAS-6 solution is appreciably weaker than the control test. The compatibility test indicates NQAS-6 could be compatible with the conventional additives in water-based drilling fluids, and the temperature resistance of modified starch was improved effectively. Meanwhile, the inhibitive mechanism was discussed through the particle distribution measurement.

Development of an Environmentally-Friendly Water-Based Mud System Using Natural Materials

Drilling muds are complex formulations of a range of chemicals designed to have specific properties under very specific drilling conditions. Environmentalists including different government and non-government agencies always have a concern regarding the conventional drilling mud system because drilling industry has no choice but to use huge amounts of chemicals as additives. These chemicals are toxic and pose an excessive threat to mankind as well as the environment. The recent priority of any drilling program considers the development of environmentally-friendly drilling fluids so that the ecology is preserved to its maximum level. This article proposes three naturally occurring materials—date seeds, powdered grass, and grass ash as possible additives in the drilling mud system. Sieve analysis and laser particle size analysis are conducted to study the particle size of the three materials. SEM–EDX analysis is performed to know the elemental composition of the proposed additives. Experimental tests on rheology and filtration are conducted at room temperature on the proposed materials to determine the applicability of these natural substitutes as drilling fluid additives. Results show that date seeds, grass, and grass ash can be used as a rheology modifier, and a filtration control agent to formulate the water-based mud system.

Shale hydration inhibition characteristics and mechanism of a new amine-based additive in water-based drilling fluids

In this work, shale hydration Inhibition performance of tallow amine ethoxylate as a shale stabilizer in water based drilling fluid, was investigated through these tests: bentonite hydration inhibition test, bentonite sedimentation test, drill cutting recovery test, dynamic linear swelling test, wettability test, isothermal water adsorption test, and zeta potential test. The results showed that bentonite particles are not capable of being hydrated or dispersed in the mediums containing tallow amine ethoxylate; tallow amine ethoxylate had shown a comparable and competitive inhibition performance with potassium chloride as a common shale stabilizer in drilling industry. Some amine functional groups exist in tallow amine ethoxylate structure which are capable of forming hydrogen bonding with surfaces of bentonite particles. This phenomenon decreased the water adsorption on bentonite particles' surfaces which results in reduction of swelling. Tallow amine ethoxylate is also compatible with other common drilling fluid additives.

Nano-Based Drilling Fluids: A Review

Nanomaterials are engineered materials with at least one dimension in the range of 1–100 nm. Nanofluids—nanoscale colloidal suspensions containing various nanomaterials—have distinctive properties and offer unprecedented potential for various sectors such as the energy, cosmetic, aerospace and biomedical industries. Due to their unique physico-chemical properties, nanoparticles are considered as very good candidates for smart drilling fluid formulation, i.e., fluids with tailor-made rheological and filtration properties. However, due to the great risk of adapting new technologies, their application in oil and gas industry is not, to date, fully implemented. Over the last few years, several researchers have examined the use of various nanoparticles, from commercial to custom made particles, to formulate drilling fluids with enhanced properties that can withstand extreme downhole environments, particularly at high pressure and high temperature (HP/HT) conditions. This article summarizes the recent progress made on the use of nanoparticles as additives in drilling fluids in order to give such fluids optimal rheological and filtration characteristics, increase shale stability and achieve wellbore strengthening. Type, size and shape of nanoparticles, volumetric concentration, addition of different surfactants and application of an external magnetic field are factors that are critically evaluated and are discussed in this article. The results obtained from various studies show that nanoparticles have a great potential to be used as drilling fluid additives in order to overcome stern drilling problems. However, there are still challenges that should be addressed in order to take full advantage of the capabilities of such particles. Finally the paper identifies and discusses opportunities for future research.

Preparation and performance of amine-tartaric salt as potential clay swelling inhibitor

A series of small molecular clay swelling inhibitor was prepared with tartaric acid and amines, presented as amine-tartaric salts (ATS). The inhibitor was screened based on the linear expansion rate of bentonite. The results show that the inhibitor prepared with tartaric acid and triethylenetetramine with the mole ratio of 1:1 (named as ATS-4) is the best inhibitor of the hydration expansion and dispersion of bentonite. The inhibitive properties of ATS-4 were evaluated by various methods, including clay linear swelling tests, anti-swelling tests, mud ball immersing tests, mud-making inhibition experiments and particle distribution measurements etc. The results show that ATS-4 has superior performance to inhibit the hydration swelling and dispersion of clays by controlling the particle size of clay. On the other hand, the bentonite linear expansion rate in 0.5% ATS-4 aqueous solution is much lower than that of others, and the hydration expansion degree of the mud ball in ATS-4 aqueous solution is appreciably weaker than the control test, and it is compatible with the conventional additives in water-based drilling fluids. Then, the inhibition mechanism of the amine-tartaric salt was well discussed based on thermogravimetric analysis (TGA), scanning electron microscope (SEM), X-ray diffraction analysis (XRD), single crystal X-ray diffraction and ion exchange tests.

Effect of barite and gas oil drilling fluid additives on the reservoir rock characteristics

This research presents a study of the effect of drilling fluid on the reservoir rock properties. The interactions between the clay minerals existing in the formations and the drilling fluids have been studied. Two types of drilling fluids, which are water-based ferrochrome lignosulfonate base mud and lime mud, were prepared for the study. About 100 core plugs were prepared from seven oil wells of Zubair Formation from depths of over (3000) m. The core plugs were cut, cleaned, dried, and then subjected to petrophysical tests, which are permeability, saturation, X-ray diffraction, and the petrographical analyses. Clay minerals like kaolinite, illite, and montmorillonite were found in the core samples. The static immersion test shows that the clay minerals reacted with the drilling fluids and created swelling and spalling in the core samples and changed the original petrophysical rock properties. Different concentrations of gas oil and barite were added to improve the properties of the used drilling fluids and to decrease their negative impact on the petrophysical rock properties. A comparison is made between the permeability and water saturation before and after exposure to the drilling fluids. The percentage change in permeability and water saturation is calculated. The results showed that the additives to the drilling fluids reduced the formations damage. Finally, the study indicates that the major formation damage in southern Iraqi oil fields is induced by mechanical and chemical mechanizes.

The Shielding Effect of Drilling Fluids on Measurement While Drilling Tool Downhole Compasses—The Effect of Drilling Fluid Composition, Contaminants, and Rheology

Materials such as added clays, weight materials, drill solids, and metallic wear products in the drilling fluid are known to distort the geomagnetic field at the location of the measurement while drilling (MWD) tool magnetometers that are used to measure the direction of well path. This distortion contributes to substantial errors in determination of azimuth while drilling deviated wells. These errors may result in missing the target of a long deviated 12 ¼ in. section in the range of 1–200 m, representing a significant cost to be mitigated. The error becomes even more pronounced if drilling occurs in arctic regions close to the magnetic north pole (or south pole). The effect on the magnetometer readings is obviously linked to the kinds and amounts of magnetic materials in the drilling fluid. The problem has recently been studied by laboratory experiments and analyses of downhole survey data. A series of experiments has been carried out to understand how some drilling fluid additives relate to the magnetic distortion. Experiments with free iron ions show that presence of iron ions does not contribute to magnetic distortion, while experiments with bentonite-based fluids show a strong effect of bentonite on magnetic shielding. Albeit earlier measurements showing a strong dependency of the content of organophilic clay, clean laboratory prepared oil-based drilling fluids show no increased shielding when adding organophilic hectorite clays. The anticipated difference between these two cases is outlined in the paper. When eroded steel from an offshore drilling site is added into the oil-based drilling fluid, it is found that these swarf and steel fines significantly increase the magnetic shielding of the drilling fluid. The paper outlines how the drilling direction may be distorted by the presence of these additives and contaminants and how this relates to the rheological properties of the drilling fluid.

The use of grass as an environmentally friendly additive in water-based drilling fluids

Excellent drilling fluid techniques are one of the significant guaranteed measures to insure safety, quality, efficiency, and speediness of drilling operations. Drilling fluids are generally discarded after the completion of drilling operations and become waste, which can have a large negative impact on the environment. Drilling materials and additives together with drill cuttings, oil, and water constitute waste drilling fluids, which ultimately are dumped onto soil, surface water, groundwater, and air. Environmental pollution is found to be a serious threat while drilling complex wells or high-temperature deep wells as these types of wells involve the use of oil-based drilling fluid systems and high-performance water-based drilling fluid systems. The preservation of the environment on a global level is now important as various organizations have set up initiatives to drive the usage of toxic chemicals as drilling fluid additives. This paper presents an approach where grass is introduced as a sustainable drilling fluid additive with no environmental problems. Simple water-based drilling fluids were formulated using bentonite, powdered grass, and water to analyze the rheological and filtration characteristics of the new drilling fluid. A particle size distribution test was conducted to determine the particle size of the grass sample by the sieve analysis method. Experiments were conducted on grass samples of 300, 90, and 35 μm to study the characteristics and behavior of the newly developed drilling fluid at room temperature. The results show that grass samples with varying particle sizes and concentrations may improve the viscosity, gel strength, and filtration of the bentonite drilling fluid. These observations recommend the use of grass as a rheological modifier, filtration control agent, and pH control agent to substitute toxic materials from drilling fluids.

Preparation and evaluation of cationic bolaform surfactants for water-based drilling fluids

Three cationic bolaform surfactants with different spacer lengths were prepared from the reaction of two moles of triisopropanolamine with one mole of each of the following 1,4-dibromobutane, 1,5-dibromopentane and 1,6-dibromohexane. The chemical structures of the prepared compounds were confirmed via: FTIR spectroscopy, 1H NMR and elemental microanalysis. The surface activity of these bolaform surfactants was studied. The prepared cationic bolaform surfactants were evaluated as viscosifier additives for water-based drilling fluids. The evaluation includes the study of rheological properties of the formulated mud (apparent viscosity, plastic viscosity and yield point, gel strength and thixotropy), effect of temperature on the rheological properties and also, the study of mineralogical properties of the water-based before and after treatment with the prepared surfactants using: X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results of the evaluation were compared to the water-based mud formulated from commercial grade bentonite.

Metal-Formed Liner Hanger Avoids High-Setting-Pressure Requirements

Seminole Services announced the commercialization of its first product, the Powerscrew Liner System, a new expandable-liner hanger that is set with torsional energy from the topdrive (Fig. 1). The Louisiana-based company began development on the tool and associated equipment in the fall of 2012. Rooted in solid mechanics and material science, the company provides engineered wellbore solutions to exploration and production companies actively engaged in drilling oil and gas wells. In the evolution of liner hangers, mechanically set systems were developed first. While many operators believe mechanical systems are more robust and provide superior sealing integrity when compared with hydraulically set hangers, older mechanical systems typically lack reliability, especially in applications requiring longer liners in deviated wellbores. In large part, this is because of the risks associated with reaming a mechanical hanger to setting depth. Reliability rates were increased with the introduction of hydraulically set hangers, which allowed a greater range of applications. However, the newer setting method suffers from its own limitations, such as flow-area restrictions, compatibility with drilling-fluid additives, and a multitude of potential leak paths. With the advent of expandable-liner hangers, further increases in setting reliability were achieved along with even greater applications. The increase in reliability stemmed, at least in part, from greater success reaming the liner to setting depth. The higher reliability of expandables is perhaps a consequence of greater flow area at the liner top and the lack of external setting devices. This has led to many new developments in drilling with liners (DWL). Nevertheless, expandable-liner hangers continue to suffer from potential leak paths associated with high hydraulic pressure sourced at the mud pumps. The hydraulic pressure provides energy to the running tool necessary in setting the liner top. In most expandable systems, pressure pushes the roller/ expansion cones/sleeve through a metal-formed tubular by use of a multitude of pressurized connections and fluid ports. By contrast, the torsionally set system combines the latest in metal-forming technology along with the best features of mechanically set systems. The result is a setting process that does not require high hydraulic pressures and eliminates the risks associated with reaming the liner to setting depth and DWL.

Cellulose Nanocrystals and Polyanionic Cellulose as Additives in Bentonite Water-Based Drilling Fluids: Rheological Modeling and Filtration Mechanisms

This research aims to develop low cost, sustainable, environmentally friendly, and high performance water-based drilling fluids (WDFs) using bentonite (BT), polyanionic cellulose (PAC), and cellulose nanocrystals (CNCs). The effect of concentration of BT, PAC, and CNCs on the rheological and filtration properties of PAC/CNC/BT-WDFs was investigated. Eight empirical rheological models were applied to fit quantitatively the fluid properties. Results showed that the presence of PAC, CNCs, and BT improved the rheological and filtration properties of the WDFs. Among the eight empirical rheological models, the Sisko model performed the best in simulating the rheological behavior of the fluids. At the same concentration level of PAC and CNCs, CNCs had more impact on the rheological properties, whereas PAC had more influence on the filtration property. The incorporation of PAC resulted in very low permeable filter cakes, leading to the excellent filtration property. The combined use of PAC and CNCs yielded better...

Effect of Sand Content on the Filter Cake Properties and Removal During Drilling Maximum Reservoir Contact Wells in Sandstone Reservoir

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%.

Evaluation of some natural water-insoluble cellulosic material as lost circulation control additives in water-based drilling fluid

Circulation losses have always been a serious and expensive problem to the drilling industry. Even with the best drilling practices circulation losses do occur. In order to reduce such losses to acceptable level fluid Loss Control Material (LCM) is used.In this work, three natural water-insoluble cellulosic materials; peanut hulls, bagasse and sawdust were investigated as lost circulation control materials. One hundred and eight different LCM samples made of various materials were tested with mud. The experiments were conducted in a permeability plugging apparatus (PPA) at a differential pressure of 100psi and 300psi, using 10, 60 and 90 ceramic discs. The performance of each LCM sample was determined based on the amount of spurt loss and total fluid loss of the mud according to the American Petroleum Institute (API) standard. The obtained results showed that, the amount of the fluid loss depends on the LCM material, concentration and size distribution, testing results show that, the peanut gives the best results among the bagasse and sawdust, especially fine size which exhibited better results in the filtration characteristics due to the better filling properties of this size. Peanut hulls, bagasse and sawdust show a slight effect on the rheological properties of the mud. The results were discussed on light of particle size distribution.

Contamination effects of drilling fluid additives on cement slurry

During the cementation of deep wells, contamination at the contact surface between cement slurry and drilling fluid will present a technical challenge, which may threaten operation safety. To deal with the problem, lab tests and analysis were performed specifically on the compatibility of fluids during cementation in Sichuan and Chongqing gas fields. Impacts of commonly used additives for drilling fluids were determined on fluidity and thickening time of conventional cement slurry. Through the infrared spectrum analysis, SEM and XRD, infrared spectrum data of kalium polyacrylamide (KPAM) and bio-viscosifier were obtained, together with infrared spectrum, SEM and XRD data of cement slurry with additives. Contamination mechanisms of the cement slurry by conventional additives for drilling fluid were reviewed. Test results show that both KPAM and bio-viscosifier are such high-molecular materials that the long chains in these materials may easily absorb cement particles in the slurry to form mixed network structures; as a result, cement particles were prone to agglomeration and eventually lost their pumpability. Finally, assessment of and testing methods for the contamination effects of drilling fluid additives on cement slurry were further improved to form standards and codes that may help solve the said problems. This study will provide technological supports for the preparation of drilling fluids with desirable properties prior to cementation, the selection of optimal drilling fluids additives, and the development of innovative drilling fluids additives.

A novel nonionic surfactant for inhibiting shale hydration

The demand for cost effective and environmentally shale inhibitor is increasing in drilling industry. This paper reports for the first time the use of Zizyphus spina-christi extract (ZSCE), a newly developed nonionic surfactant, for inhibiting shale hydration. The adsorption behavior of ZSCE onto shale cuttings was determined through conductivity technique. Adsorption isotherm coincides with the characteristics of Freundlich isotherm. The inhibitive property of ZSCE was assessed through a number of inhibition evaluation methods. All experimental findings verify that ZSCE can act as a potential shale inhibitor; nevertheless, its inhibitive potential has no significant improvement at concentrations above the CMC. Moreover, ZSCE has a better performance compared to potassium chloride and polyamine. According to compatibility tests, the ZSCE is compatible with conventional water-based drilling fluids (WBDF) additives. Scanning electron microscopy (SEM) observations clearly indicate the stability of sodium bentonite particles in ZSCE aqueous solution. The hydrogen bonding between hydrophilic tail of ZSCE molecules and oxygen atoms available on silica surface of clay, which results in formation of hydrophobic shell on the clay surface, is believed to be the main inhibition mechanism for ZSCE. This research paves the way for selection and implementation of surfactants, especially plant-based, as shale inhibitors in WBDF.

The influence of sulfomethyl phenol formaldehyde resin (SMP) on cementing slurry

The poor compatibility between drilling fluid additives and cementing slurry can lead to downhole accidents and inferior cementing quality. Therefore, this paper intends to study on the influence of sulfomethyl phenol formaldehyde resin (SMP) on cement slurry. This paper studies the influence of SMP on the rheological property, thickening time, aggregate stability of cement slurry, and compressive strength of cement stone, and studies the influence of SMP on the concentration of metal ions of cement slurry. And this paper analyzes the influence of SMP on the microstructure of cement slurry via vacuum freeze-dry technology of liquefied nitrogen combined with environmental scanning electron microscope. Finally draw the conclusions: SMP and metal ions with high valence (Fe3+, etc.) set off complexation reaction in cement slurry, which increases the molecular weight of complex compound adsorbed on the surface of the cement particles. Meanwhile, Zeta potential is decreased after SMP is added to cement slurry, and the cement slurry becomes thickened as the particles move from agglomeration and diffusion equilibrium towards aggregation direction. After SMP and metal ions with high valence (Fe3+, … etc.) set off the complexation reaction in cement slurry, a dense “film” is formed on the surface of the particles to prevent cement particles from contacting free water, which will reduce the hydration rate of cement particles, increase the thickening time of cement slurry, and reduce the compressive strength of the cement stone to only two-fifth of the compressive strength of cement stone with original formula.

A survey on cationic polyelectrolytes and their applications: acrylamide derivatives

AbstractCationic polyelectrolytes are water-soluble polymers bearing positive ionic groups along the backbone or in side chains. These cationic polymers are synthesized by free radical polymerization of acrylamide and their derivatives by the copolymerization method, which includes solution, precipitation, and emulsion techniques. The Mannich reaction is another important method by which the cationic polymers can be processed. In this review paper, the preparation methods, interaction mechanisms of these polymers, and their popular industrial applications are summarized. These polymers open a lot of applications in different fields such as paper-making processes, water and wastewater treatment, oil and drilling industries, mineral separation, paint and food industries, cosmetics, and pharmacy. In addition, these polymers are widely used as flocculants and rheology control agents. These polymers are especially employed in oil field operations as viscosity control agents for enhanced oil recovery, drilling fluid additives, and also for modifying flow and stability properties of aqueous solutions and gels. They are used as super-plasticizers, which affect the rheological properties of dense cement suspensions. Mining processes also benefit from the use of acrylamide derivative polymers to flocculate solids in aqueous dispersions. The cationic polymers may interact with different components in the system such as inorganic/organic particles in aqueous dispersions in several ways, which may result in the stability or instability of dispersion. The particles can be destabilized through three different main mechanisms which promote flocculation: polymer bridging, charge neutralization, and polymer adsorption.

An improved estimation of shear rate for yield stress fluids using rotating concentric cylinder Fann viscometer

Abstract This paper deals with the estimation of wall shear rates for yield stress fluids using rotating coaxial-cylinder viscometer readings. The estimation is based on the generalized difference equation for rotating narrow gap coaxial cylinder Fann Viscometer under purely steady, laminar and isothermal tangential fluid flow condition. Rotor rotations and bob deflections are the two important viscometer readings and these are used to predict wall shear rates. The proposed equations are used to calculate shear rates for several Herschel–Bulkley type fluids involving polymer (for example, xanthan gum, poly-anionic cellulose and carbomethoxy cellulose) solutions with varying concentration and bentonite suspension, which are frequently used as drilling fluid additives. Parametric sensitivity is made for stability analysis of the proposed shear rate equations. Finally, the predicted shear rates are compared with the conventional method of estimating the rate of shear for drilling fluids.