Yield stress fluids are encountered in a wide range of applications: toothpastes, cements, mortars, foams, muds, mayonnaise, etc. The fundamental character of these fluids is that they are able to flow (i.e., deform indefinitely) only if they are submitted to a stress above some critical value. Otherwise they deform in a finite way like solids. The flow characteristics of such materials are difficult to predict as they involve permanent or transient solid and liquid regions that are generally hard to locate a priori. Here we review the present state of the art as it appears from experimental data for flows of simple (non-thixotropic) yield stress fluids under various conditions, viz., uniform flows in straight channels or rheometrical geometries, complex stationary flows in channels of varying cross-section such as extrusion, expansion, flow through a porous medium, transient flows such as flows around obstacles, spreading, spin-coating, squeeze flow, and elongation. The effects of surface tension, confinement, and secondary flows are also reviewed. We focus especially on experimental work identifying internal flow characteristics that can be compared with numerical predictions. It is shown in particular that: (i) deformations in the solid regime can play a critical role in transient flows; (ii) the yield character is not apparent in the flow field when the boundary conditions impose large deformations; (iii) the yield character is lost in secondary flows.

Yield stress fluid flows: A review of experimental data

Yield stress fluid flows occur in a great many operations and unit processes within the oil and gas industry. This paper reviews this usage within reservoir flows of heavy oil, drilling fluids and operations, wellbore cementing, hydraulic fracturing and some open-hole completions, sealing/remedial operations, e.g., squeeze cementing, lost circulation, and waxy crude oils and flow assurance, both wax deposition and restart issues. We outline both rheological aspects and relevant fluid mechanics issues, focusing primarily on yield stress fluids and related phenomena.

/pdf/bingham-s-model-in-the-oil-and-gas-industry-vpmb7xhs1m.pdf

Bingham’s model in the oil and gas industry

A state-of-the-art review of the application of nanotechnology in the oil and gas industry with a focus on drilling engineering

A comprehensive review on the loss of wellbore integrity due to cement failure and available remedial methods

We consider laminar displacement flows in narrow eccentric annuli, oriented horizontally, between two fluids of Herschel–Bulkley type, (i.e. including Newtonian, power-law and Bingham models). This situation is modelled via a Hele-Shaw approach. Whereas slumping and stratification would be expected in the absence of any imposed flow rate, for a displacement flow we show that there are often steady-state travelling wave solutions in this displacement. These may exist even at large eccentricities and for large density differences between the fluids. When heavy fluids displace light fluids, annular eccentricity opposes buoyancy and steady states are more prevalent than when light fluids displace heavy fluids. For large ratios of buoyancy forces to viscous forces we derive a lubrication-style displacement model. This simplification allows us to find necessary and sufficient conditions under which a displacement can be steady, which can be expressed conveniently in terms of a consistency ratio. It is interesting that buoyancy does not appear in the critical conditions for a horizontal well. Instead a competition between fluid rheologies and eccentricity is the determining factor. Buoyancy acts only to determine the axial length of the steady-state profile.

Viscoplastic fluid displacements in horizontal narrow eccentric annuli: stratification and travelling wave solutions


 During well cementing and drilling operations, proper control of downhole pressure is critical for controlling the well, i.e. avoiding formation fluids influx or fracturing the formation, and hence ensuring successful well construction operations. At the planning stage, well control is investigated using numerical hydraulics simulations. During actual operations, annular pressure-while-drilling (APWD) is often, but not systematically, available while drilling but not while cementing. Here again well control relies on simulations. Accurate prediction of downhole pressures is therefore a key requirement for well control, whether at the planning stage or in real-time during operations.
 Fluid properties are a key input to the hydraulics simulations, in particular fluid viscosity, which is required to estimate friction pressure losses. A difficulty is the dependence of viscosity on pressure and temperature. At a given shear rate, the viscosity of drilling and cementing fluids continuously changes within the flow path, and variations of several tens of percent are common. Hence it is paramount to measure cementing and drilling fluids viscosity over the pressure and temperature domain that will be experienced in the well, but also to fit to the measurements a pressure and temperature dependent rheological model that will allow the hydraulics simulator to obtain viscosity at any shear rate, temperature, and pressure values.
 We first provide an overview of the algorithms needed to analyze rheological lab measurements, where care must be taken to account for potential wall slip effects. We then review how to account for pressure and temperature effects, via the use of Arrhenius and Barus laws, and why the modeling needs should inform the test requirements.

Practical Application of Pressure and Temperature Dependent Viscosity Calculations in Well Cementing Simulations

We present new results on the laminar displacement of Herschel-Bulkley fluids along narrow eccentric annuli. We adopt a Hele-Shaw modelling approach and consider the possibility that a long displacement finger should advance along the wide side of the annulus. We deduce conditions under which this cannot happen. We also analyse local instability of the interface on wide and narrow sides of the annulus using the Muskat approach

Visco-plastic fluid displacements in near-vertical narrow eccentric annuli: prediction of travelling-wave solutions and interfacial instability

Uncontrolled flows of reservoir fluids behind the casing are relatively common. In worst cases these can lead to blow out, leakage at surface, destruction of subsurface ecology and potential freshwater contamination. Often, safe abandonment of such wells is not possible. A significant cause of flows behind the casing is ineffective mud removal during primary cementing. The ideal situation is that drilling mud is displaced all around the annulus and that the displacement front advances steadily up the well at the pumping velocity. Even better is that the wide and narrow sides of the front advance at the same speed. Conversely, if the fluid on the narrow side of the annulus does not move, or moves very slowly, a longitudinal mud channel can result. Although the possibility of a narrow side mud channel and benefits of a steady state displacement have been recognised since the mid-1960s, there is still little quantitative understanding of when steady state displacements occur. In this paper we present new results on the displacement of cementing fluids along eccentric annuli. We show that for certain combinations of the physical properties there will be a steady state displacement front. Furthermore, we are able to give an analytical expression for the shape of the front and indications of how the shape changes with the key physical parameters of the cementing process. These results are novel and have interesting implications for effective mud removal and complete zonal isolation during primary cementing. Introduction Primary cementing is a critically important operation in the construction of any oil well, (Ref. 1). Apart from providing structural integrity to the well, the chief purpose of the operation is to provide a continuous impermeable hydraulic seal in the annulus, preventing uncontrolled flow of reservoir fluids behind the casing. Serious problems may arise from such flows. Gas or oil may flow to surface causing a blowout, with consequent environmental damage and possible loss of life. Fluid migration into subsurface aquifers can cause contamination of drinking water, or can affect near-wellbore ecology. Even if surface casing vent flows are contained within the annulus, the fact of having pressure at surface prevents a well from being permanently abandoned, i.e. safely, at the end of its lifetime. Instead, these wells become permanently shut-in and remain an environmental risk. Financial consequences of poor zonal isolation on reservoir production are of course well known. A widely cited industry figure, (Ref. 2), is that 15% of primary cementing jobs carried out in the US fail and that about 1/3 of these failures are due to gas or fluid migration. This problem exists worldwide, (e.g. about 9000 wells are suspended or temporarily abandoned in the U.S. Gulf Coast region). It is also particularly acute in Western Canada, where around 34,000 wells are currently shut-in and suspended, (Ref. 3), unable to be permanently abandoned due to gas pressures at surface, between the casing and formation, in the cement. Local variations in this problem can be extreme. For example, field survey results reported in Ref. 4, from Tangleflags, Wildmere and Abbey, (3 areas in Eastern Alberta), reveal that over a number of years, 0-12% (Tangleflags), 0-15% (Wildmere), and 80% (Abbey) of wells have been leaking in these regions. One known cause of surface casing vent flows is that the cement, which is placed in the annulus between the outside of the casing and the inside of the hole, fails to fully displace the drilling mud that initially occupies this space. Incomplete mud removal can manifest in different ways. First, a coherent mud channel can form on the narrow side of the eccentric annulus. Second, residual mud or spacer can contaminate the cement as it sets. Third, mud may remain static in layers stuck to the inner and outer walls of the annulus. In the first or last case, the residual mud dehydrates as the cement sets and allows a porous conduit to develop in the annulus. In the case of severe contamination, the cement may not properly set. These problems and the consequences described, provide the main motivation for this paper. This paper focuses on avoiding all three above cases, by ensuring that the initial displacement is steady. Unless there are significant losses during primary cementing, a steady stable displacement front advancing at the mean pumping speed all around the annulus is sufficient to ensure that the displacement is effective. Therefore, we consider the important question of whether these displacement fronts can be found in a realistic mathematical model of the process. Certainly, physical intuition tells us that certain simple cases should have steady displacement profiles, e.g. a heavy viscous fluid displacing a lighter less viscous fluid in a SPE 80999 Effective and Ineffective Strategies for Mud Removal and Cement Slurry Design I.A. Frigaard, SPE, University of British Columbia, and S. Pelipenko, Schlumberger

Effective and Ineffective Strategies for Mud Removal and Cement Slurry Design

We consider a two-dimensional Hele-Shaw type model for displacement flows occurring in the primary cementing of an oil well. The fluids are visco-plastic and may get stuck in the annulus if a critical pressure gradient is not exceeded. The model consists of solving a nonlinear elliptic variational inequality equation for the stream function, coupled to an equation for interface advection, or alternatively a concentration equation for the mass fraction of each fluid. The key difficulty is to accurately compute yielded and unyielded zones of the wellbore fluids, which we accomplish by use of an augmented Lagrangian method to solve the stream function equation. We validate the accuracy of our method against analytical solutions for stable steady-state displacements. We study the convergence of the interface to the steady state, showing that the apparent meta-stability is illusory. We then explore the effects of increasing eccentricity, showing that although the interface may remain stable it becomes unsteady. Initially fully mobile flows are found, but as the eccentricity increases further the narrow side fluids fail to move in the far field. The narrow side interface can progress slowly through the static fluids by a burrowing motion, but for still larger eccentricities even the interface becomes static and a narrow-side mud channel forms.

Two-dimensional computational simulation of eccentric annular cementing displacements

Uncontrolled flows of reservoir fluids behind the casing are relatively common in primary cementing and can lead to any of the following: blowout, leakage at surface, destruction of subsurface ecology, potential contamination of freshwater, delayed or prevented abandonment, as well as loss of revenue due to reduced reservoir pressures. One significant potential cause is ineffective mud removal during primary cementing. Ideally, the drilling mud is displaced all around the annulus and the displacement front advances steadily up the well at the pumping velocity. This paper addresses the question of whether or not such steady-state displacements can be found for a given set of process parameters.

Mud removal and cement placement during primary cementing of an oil well - Part 2; steady-state displacements

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