Improvements in Drilling Fluid Rheology Predictions Using Rotational Viscometer

The effects of apparent wall slip on rheometric measurements of waxy gels are quantified for gels consisting of a macrocrystalline wax added in mineral oil in concentrations of 3.0 and 7.5 wt. %. The waxy gels are formed in situ in a stress-controlled rheometer, and rheological properties are then obtained. Seven different geometry configurations, including parallel plates, concentric cylinders, and vane, are employed. The surface roughness of the different geometries and wax crystals size are assessed to provide insight into the apparent wall slip phenomenon. In the presence of smooth surfaces, a decrease in approximately 80% in the measured yield stress value is observed in oscillatory tests, regardless of system composition. In addition, the storage modulus measurements are substantially different when obtained from smooth or grooved geometries. In creep experiments, the yield stress measurements decrease by 68%. As expected, apparent wall slip markedly affects the shape of the flow curves obtained, causing the appearance of kinks for smooth Couette geometry. Apparent slip velocities are calculated in the regime just above the yield stress, and it is found that for low concentrations apparent slip increases with concentration and decreases with the ratio between the shear stress and dynamic yield stress. The gathered results also demonstrate that the reproducibility of rheological measurements is improved by using geometries with grooved parts. By quantifying the effects of apparent wall slip on rheological measurements of waxy gels for different geometries, this work can provide useful information for the design of pipelines and oil transportation processes.

A new way is suggested for treatment of the viscometric data, obtained in a rotational viscometer using several configurations of coaxial cylinders with different gap widths. Liquids are assumed to display both a general shear-thinning behavior and an apparent slip at solid boundaries. The body of primary data is at first smoothed using a conventional least-squares fitting. The subsequent procedure, called local filtering, gives a nonparametric representation of the both material functions γ̇=γ̇(τ) and u=u(τ). Several data sets for aqueous polymeric solutions with high content of electrolytes are treated to demonstrate the typical problems encountered in analyzing apparent wall-slip effects. When compared with the data found in literature, the slip velocities obtained are slightly higher, probably due to an enhanced coagulation caused by the presence of electrolytes.

We employ a recently proposed viscosity function (Souza Mendes and Dutra, 2004) to analyze the fully developed flow of yield-stress liquids through tubes. We first show that its dimensionless form gives rise to the so-called jump number, a novel material property that measures the shear rate jump that the material undergoes as the yield stress is reached. We integrate numerically the momentum conservation equation that governs this flow together with the generalized Newtonian Liquid model and the above mentioned viscosity function. We obtain velocity and viscosity profiles for the entire range of the jump number. We show that the friction factor f.Re curves display sharp peaks as the shear stress value at the tube wall approaches the yield stress. Finally, we demonstrate the existence of sharp flow rate increases (or apparent slip) as the wall shear stress is increased in the vicinity of the yield stress.

Viscosity of API/fatty acid suspensions: Pitfalls during analysis.

Experimental evidence of wall slip in lubricated contacts sometimes leads to reconsider the usual no-slip conditions. The main theoretical slip conditions found in literature depend on parameters (shear stress threshold, slip length, etc.) to which calculated friction is directly related. A different point of view, on which this work is focused, considers that the apparent wall shear rate is only representative of the bulk flow, and assumes the existence of wall layers, which define the actual local shear rate and friction. The aim of this exploratory work is to build a generalized Reynolds model, with no-slip wall conditions, able to simulate situations of either slip or immobile layers. A very simple ‘rheological’ model, consisting of different Newtonian viscosities in the bulk flow and in wall layers is used. By varying the orders of magnitude of the layers’ thicknesses and viscosities, it is possible to capture all possibilities between apparent wall slip and immobile layers. The model is applied to a plane pad bearing at a prescribed load, and revealed two modes of velocity accommodation giving friction forces significantly smaller than those for a mono-layered film: plug flow with apparent wall slip or middle slip layers.

Neutralized 0.5% microgels of the crosslinked copolymer of methyl vinyl ether and maleic anhydride were characterized by the penetrating ball test and by Brookfield viscometry with the # 7 cylindrical, T-E, and flag-impeller spindles. Apparent wall slip between the microgel and the #7 cylindrical spindle is a surface phenomenon that is more pronounced for “hard” microgels than for “soft” microgels and depends strongly on the interaction between the surface of the spindle and the microgel. Apparent wall slip can be enhanced by coating the #7 spindle with hydrophobic polymers and polymers with carboxyl groups and suppressed by coating the spindle with vinylpyrrolidone-based polymers. Similar apparent wall slip was also noticed for the cross-linked polyacrylic acid microgel. Apparent wall slip was not noticed when the T-E spindle and the flag-impeller spindle were used in viscosity measurement. The viscosity of microgels measured with a #7 spindle coated with polyvinylpyrrolidone, a T-E spindle, and a flag-impeller spindle correlate well with each other, indicating that the apparent wall slip is suppressed equally well by these three spindles. A simple penetrating ball test was used to differentiate hard microgels from soft microgels. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 67–74, 1999

The influence of different electrolytes on the apparent wall slip (AWS) of aqueous kaolin suspensions is studied experimentally. The fluidity and AWS characteristics of purely aqueous and deflocculated kaolin suspensions are measured by gap-dependent rotational viscometry using unconventional cone–cone geometry. The applied sensors are made of different materials: stainless steel (smooth and sandblasted), titanium, and duralumin (with an anodized surface). Both the quality of the sensor surface and the presence of electrolytes strongly influence the observed AWS behavior. In the case of a purely aqueous 40% kaolin suspension, positive AWS (depleted layer formation) is measured on the stainless steel and titanium sensors, while negative AWS (stagnant layer formation) is observed on the anodized duralumin sensor. In the case of fully deflocculated suspensions, Newtonian flow behavior is observed with almost no measurable AWS effects. In the case of partially deflocculated suspensions, the type of deflocculant becomes important. While the presence of Na2CO3 or NaOH does not qualitatively change the AWS trends and only slightly increases them, the presence of SHMP (sodium hexametaphosphate) leads to positive AWS on anodized duralumin. However, the addition of NaCMC (sodium salt of carboxymethylcellulose) induces negative AWS on all the surfaces studied.

Bulk fluidity and apparent wall slip of aqueous kaolin suspensions studied using the cone-cone (KK) sensor: Effect of the sensor surface quality

For avoiding environmental pollution, predominantly water based drilling fluids are employed in drilling operations. If these drilling fluids contain clays as structural agents, contamination by electrolytes or exposure to elevated temperature, or both, can result in more or less severe flocculation and thickening; this phenomenon can cause serious problems during the resumption of circulation, especially after long round trips, as well as swab and surge. For this reason, it is especially important in practice to be capable of predicting the long-term gelation behavior of the drilling fluid on the basis of short-term gel strength measurements. In the present study, it has been shown that reproducible gel data can be obtained only in exceptional cases on water-based clay drilling fluids exposed to electrolytes or elevated temperature, or both, with the use of measuring instruments standardized in conformance with API (such as the Fann V-G Meter, model 35). On the other hand, it has been shown that arbitrarily high gel strength values can be determined reproducibly with the ITE instrument for measuring gel strength of clay suspensions (GMT), because the apparent wall slip is eliminated. On the basis of short-term gel strength values measured with the ITE GMT, the long-term gelation behavior of water-based clay drilling fluids can be predicted with sufficient accuracy by means of the analytical method introduced by Garrison in 1938; this is of particular interest especially after lengthy round trips. Introduction For reasons of environmental protection, water-based drilling fluids are now being used to an increasing extent in drilling operations, even under difficult drilling conditions. As a rule, clays are employed as structural agents in these drilling fluids. For stabilizing the clay against electrolytes or elevated temperatures, or both, protective colloids are added. As a result, the polymers impose their flow behavior on the clay; that is, the differential (true) viscosity of the clay suspensions treated with polymers decreases as a function of the shear stress. Consequently, the clay is then responsible only for the value of the yield point in these systems. If water-based drilling fluids are exposed to electrolytes or elevated temperatures, or both, the protective action of the added polymers may be inhibited; as a result, the flow and gelation behavior of the clay may break through. Especially during long round trip times, the severely gelled drilling fluid can then cause problems with the pumping pressure necessary for resuming the circulation as well as with swab and surge. Hence, there is a need for reliable measuring methods and analytical techniques for predicting the long-term development of the gel strength. In the present study, the standardized API methods for measuring gel strength are first examined for reproducibility of the results. If appropriate measures prove necessary, suitable methods are developed and investigated for measuring the gel strength. Finally, the analytical method of Garrison(1) is examined for its applicability in calculating the long-term gel strength from the results of short-term measurements.

Multiphase fluids and highly non-Newtonian fluids often show wall slip. The typical approach to reduce wall slip in experiments is to use roughened geometries, which are thin porous layers. However, the presence of the roughness introduces in itself an apparent wall slip due to the flow within the porous layer. To account for wall slip typically, measurements must be run at several gaps in a plate-plate device. With Newtonian fluids, the apparent wall slip can be conveniently accounted for in the measurements at a single gap since it can be accurately predicted using models describing the flow of Newtonian fluids through and over porous media. Here, we extend this approach to viscoelastic fluids by using Minale's model [Phys. Fluids 28, 023102 and 023103 (2016)] for the flow of second order fluids (SOFs) through and over a porous medium. In this work, we first validate the theoretical predictions and then propose an experimental protocol to measure a SOF with rough geometries by executing the experiments at a single chosen gap. Two Boger fluids are used as model SOFs, and three different rough geometries are considered: Two commercial crosshatched plates and a homemade pillared one. The apparent wall slip is shown to be reduced for the viscoelastic fluids, with respect to the Newtonian case, and agreement with the theoretical predictions is excellent.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Stephen J. Gibbs, Kieran L. James, Laurance D. Hall, Derek E. Haycock, William J. Frith, Stephen Ablett; Rheometry and detection of apparent wall slip for Poiseuille flow of polymer solutions and particulate dispersions by nuclear magnetic resonance velocimetry. J. Rheol. 1 May 1996; 40 (3): 425–440. https://doi.org/10.1122/1.550752 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe Society of RheologyJournal of Rheology Search Advanced Search |Citation Search

Study on the influence of surface roughness on wall slip effect (in rheological measurement) of magnetic fluid

We investigated an explanation for the length dependence of apparent wall slip in capillary and slit die experiments that had been implied in earlier studies. Firstly, we used a very long slit die fitted with six equidistant pressure transducers and an adjustable outlet. It was found that, all other parameters being equal, the impact of pressure on the flow behavior of suspensions was not different from the impact on the unfilled matrix fluid. Particle-related properties, such as apparent wall slip, were therefore not influenced by pressure as assumed by other authors. Secondly, we determined wall slip velocities by both the Mooney method and numerical simulation, based on an implementation of Phillips constitutive equation for particle migration. This led to a similar length dependence of wall slip as had been reported in an earlier work. We concluded that this was due to the transient nature of particle migration and its interrelationship with apparent wall slip, rather than an influence of pressure.

Conventional rheometry coupled with local velocity measurements (ultrasonic Doppler velocimetry) are used to study the flow behaviour of various commercial pulp fibre suspensions at fibre mass concentrations ranging from 1 to 5 wt.%. Experimental data obtained using a stress-controlled rheometer by implementing a vane in large cup geometry exhibits apparent yield stress values which are lower than those predicted before mainly due to existence of apparent slip. Pulp suspensions exhibit shear-thinning behaviour up to a high shear rate value after which Newtonian behaviour prevails. Local velocity measurements prove the existence of significant wall slippage at the vane surface. The velocimetry technique is also used to study the influence of pH and lignin content on the flow behaviour of pulp suspensions. The Herschel–Bulkley constitutive equation is used to fit the local steady-state velocity profiles and to predict the steady-state flow curves obtained by conventional rheometry. Consistency between the various sets of data is found for all suspensions studied, including apparent yield stress, apparent wall slip and complete flow curves.

The concept of apparent wall slip (AWS) was used ad hoc for the viscometric flows with constant wall shear stress, see Oldroyd (1955). Effect of AWS in parallel-plate viscometer (PPV), a situation with varying wall shear stress, was considered by Yoshimura (1988) and by Wein (1994) in a narrowgap approximation (NGA) without stating correctly the related 2D problem. We formulate here correct AWS boundary conditions for viscometric flows. We confirm that the NG approximation is accurate enough for treating primary data from the PPV.