Off-Bottom Plug Placement: How It Works?

2020 ◽  
Author(s):  
Abdallah Ghazal ◽  
Ida Karimfazli
Keyword(s):  
Injection Site ◽  
Numerical Simulations ◽  
Fresh Water ◽  
Mixed Layer ◽  
Fluid Motion ◽  
Water Layer ◽  
Viscoplastic Fluid ◽  
Cement Slurry ◽  
Hydrodynamic Models ◽  
Two Fluids

Abstract In Canada, the Alberta Energy Regulator’s (AER) liability report, issued in 2018, predicted that the number of inactive wells in the province will double by 2030. Despite the increase in the number of inactive wells, there is a need to close them properly to avoid hazards escape. Various aspects of well plug technologies in the Canadian abandoning industry are empirical. Many plugs are formed by injecting cement slurry into wells that are otherwise filled with fresh water for the slurry to build up on top of a water layer at a desired location. However, cement is heavier than water. Thus, successful plug placement following this methodology is questionable from the hydrodynamics perspective. The present study aims to identify features of successful processes for placement of off-bottom plugs. To that end, we investigate mixing of fluids of different densities as the denser fluid is injected into the lighter fluid. Cement slurry is modeled as a viscoplastic fluid. The fluid motion is governed by hydrodynamic models, and the two fluids (i.e. cement and water) are considered to be miscible and are allowed to mix. Systematic numerical simulations aim to reveal how the characteristics of cement and the well configuration affect the placement process. We show that successful plug placement depends on the formation of a mixed layer, of the wellbore fluid and cement slurry, below the injection site. We identify and provide representative cases of the processes promoting the formation of the mixed layer: high diffusion and growing instabilities.

Placing Off-Bottom Cement Plugs: Effects of Domain Geometry

2021 ◽  
Author(s):  
Abdallah Ghazal ◽  
Ida Karimfazli
Keyword(s):  
Numerical Simulations ◽  
Open Source ◽  
Mixed Layer ◽  
Cement Slurry ◽  
Hydrodynamic Models ◽  
Injection Point ◽  
Injection Process ◽  
Flow Through ◽  
Flow Domain ◽  
Cement Plug

Abstract Oil wells are often abandoned when they become uneconomic. Normally, several cement plugs should be placed along cased wells to seal the producing formations. Proper placement protocols, especially for off-bottom plugs, are therefore required to prevent the seepage of oil. Often, heavy cement slurry is injected into wells filled with lighter wellbore fluids, through a centralised tube. To form the cement plug successfully, the injected cement slurry should accumulate at the target zone, over wellbore fluids that typically have a lower density. Therefore, the current practices involve a major hydrodynamic challenge that can result in failing plugs. In a previous work, we had shown that injecting cement slurry in wellbore fluids can result in developing a cement finger that advects downstream the well. The finger then breaks and aids the formation of a mixed layer below the injection point. Consequently, the injected cement slurry starts accumulating to form the plug. These flow events were observed in a symmetrical flow domain. In this study, we consider different configurations of the injection process to investigate how the previously observed dynamics change. To that end, we consider different sizes and positions of the injector inside the well. We conduct numerical simulations based on representative hydrodynamic models using OpenFOAM, an open source CFD software. The preliminary results reveal broadly similar dynamics for symmetrical flow domains of different injector sizes. However, marked differences are observed when the injector is not centralized in the well. The injected fluid diverts directly into the gap between the injector and casing walls, with preference to flow through the wider gap side.

The Research and Application of Cementing Isolation Technology in High Porosity and Permeability of Developed Clastic Rock Reservoir in Tarim Basin

2021 ◽  
Author(s):  
Hongtao Liu ◽  
Zhengqing Ai ◽  
Jingcheng Zhang ◽  
Zhongtao Yuan ◽  
Jianguo Zeng ◽  
...  
Keyword(s):  
Drilling Fluid ◽  
Water Layer ◽  
High Porosity ◽  
Self Healing ◽  
Cement Slurry ◽  
Clastic Rock ◽  
Pump Rate ◽  
Porosity And Permeability ◽  
Zonal Isolation ◽  
High Pump

Abstract The average porosity and permeability in the developed clastic rock reservoir in Tarim oilfield in China is 22.16% and 689.85×10-3 μm2. The isolation layer thickness between water layer and oil layer is less than 2 meters. The pressure of oil layer is 0.99 g/cm3, and the pressure of bottom water layer is 1.22 g/cm3, the pressure difference between them is as bigger as 12 to 23 MPa. It is difficult to achieve the layer isolation between the water layer and oil layer. To solve the zonal isolation difficulty and reduce permeable loss risk in clastic reservoir with high porosity and permeability, matrix anti-invasion additive, self-innovate plugging ability material of slurry, self-healing slurry, open-hole packer outside the casing, design and control technology of cement slurry performance, optimizing casing centralizer location technology and displacement with high pump rate has been developed and successfully applied. The results show that: First, the additive with physical and chemical crosslinking structure matrix anti-invasion is developed. The additive has the characteristics of anti-dilution, low thixotropy, low water loss and short transition, and can seal the water layer quickly. Second, the plugging material in the slurry has a better plugging performance and could reduce the permeability of artificial core by 70-80% in the testing evaluation. Third, the self-healing cement slurry system can quickly seal the fracture and prevent the fluid from flowing, and can ensuring the long-term effective sealing of the reservoir. Fourth, By strict control of the thickening time (operation time) and consistency (20-25 Bc), the cement slurry can realize zonal isolation quickly, which has achieved the purpose of quickly sealing off the water layer and reduced the risk of permeable loss. And the casing centralizers are used to ensure that the standoff ratio of oil and water layer is above 67%. The displacement with high pump rate (2 m3/min, to ensure the annular return velocity more than 1.2 m/s) can efficiently clean the wellbore by diluting the drilling fluid and washing the mud cake, and can improve the displacement efficiency. The cementing technology has been successfully applied in 100 wells in Tarim Oilfield. The qualification rate and high quality rate is 87.9% and 69% in 2019, and achieve zone isolation. No water has been produced after the oil testing and the water content has decreased to 7% after production. With the cementing technology, we have improved zonal isolation, increased the crude oil production and increased the benefit of oil.

The evolution of under-ice melt ponds, or double diffusion at the freezing point

1974 ◽  
Vol 64 (3) ◽  
pp. 507-528 ◽  
Author(s):  
Seelye Martin ◽  
Peter Kauffman
Keyword(s):  
Fresh Water ◽  
Sea Water ◽  
Freezing Point ◽  
Salt Water ◽  
Ice Sheet ◽  
Water Layer ◽  
Double Diffusion ◽  
Theoretical Models ◽  
Interfacial Region ◽  
Ice Melt

In an experimental and theoretical study, we model a phenomenon observed in the summer Arctic, where a fresh-water layer at a temperature of 0°C floats both over a sea-water layer at its freezing point and under an ice layer. Our results show that the ice growth in this system takes place in three phases. First, because the fresh-water density decreases upon supercooling, the rapid diffusion of heat relative to salt from the fresh to the salt water causes a density inversion and thereby generates a high Rayleigh number convection in the fresh water. In this convection, supercooled water rises to the ice layer, where it nucleates into thin vertical interlocking ice crystals. When these sheets grow down to the interface, supercooling ceases. Second, the presence of the vertical ice sheets both constrains the temperatureTand salinitysto lie on the freezing curve and allows them to diffuse in the vertical. In the interfacial region, the combination of these processes generates a lateral crystal growth, which continues until a horizontal ice sheet forms. Third, because of theTandsgradients in the sea water below this ice sheet, the horizontal sheet both migrates upwards and increases in thickness. From one-dimensional theoretical models of the first two phases, we find that the heat-transfer rates are 5–10 times those calculated for classic thermal diffusion.

Experimental Measurements and Numerical Simulations of Two-Phase Stratified, Wavy and Slug Flow in a Narrow Rectangular Channel

2005 ◽  
Author(s):  
Steven P. O’Halloran ◽  
B. Terry Beck ◽  
Mohammad H. Hosni ◽  
Steven J. Eckels
Keyword(s):  
Numerical Simulations ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Measurement Techniques ◽  
Narrow Channel ◽  
Experimental Measurements ◽  
Phase Flow ◽  
Two Phase ◽  
Two Fluids

Flow pattern transitions in two-phase flow are important phenomena for many different types of engineering applications, including heat exchangers. While two-phase flow is not understood as well as single-phase flow, advancements in both measurement techniques and numerical simulations are helping to increase the understanding of two-phase flow. In this paper, stratified/wavy flow is investigated, along with the transition from wavy to slug flow. For the experimental setup, a narrow channel with a length of 600 mm, height of 40 mm, and a width of 15 mm was fabricated using clear acrylic plastic, and water and air were the two fluids used for testing. The water in the channel was initially at rest, and the transition in flow patterns was created by increasing the velocity of air flowing over the water surface. Particle image velocimetry (PIV) was used to measure the velocity of the flow for stratified and wavy flow conditions, and also the velocity at the onset of slug flow. Along with the experimental measurements, computational fluid dynamics (CFD) simulations were conducted on a similar geometry using the volume of fluid (VOF) two-phase model. A commercial CFD software package was used for the simulations, and comparisons were made between the experimental measurements and numerical results. Favorable agreement was found between the experimental measurements and the numerical simulations. In particular, the transition from wavy to slug flow compared well to previously developed two-phase flow transition models, including the slug transition developed by Taitel and Dukler.

Inertia flows of Bingham fluids through a planar channel: Hydroelastic instability analysis

2017 ◽  
Vol 232 (13) ◽  
pp. 2394-2403 ◽  
Author(s):  
Shapour Jafargholinejad ◽  
Mohammad Najafi
Keyword(s):  
Fluid Motion ◽  
State Solution ◽  
Viscoplastic Fluid ◽  
Polymeric Coating ◽  
Dropping Out ◽  
Bingham Fluids ◽  
Bingham Number ◽  
Polymeric Gel ◽  
Pressure Driven Flow ◽  
Pressure Driven

In this paper, the effect of inertial terms on hydroelastic stability of a pressure-driven flow of a viscoplastic fluid flowing through a channel lined with a highly compliant polymeric gel is investigated. It is assumed that the fluid obeys the Bingham constuitive equation and the polymeric gel follows a two-constant Mooney–Rivlin material, which is used for modeling a nonviscous hyperelastic polymeric coating. A base-state solution is obtained for the fluid motion and solid deformation, simultaneously. Next, some infinitesimally small two-dimensional disturbances are imposed on the base-state solution. Dropping out all nonlinear perturbation terms, the modal linear stability analysis of the channel flow is conducted. The effects of the Bingham number and material constants are then examined on the critical Reynolds number. It is found that the yield stress has a stabilizing effect while the Mooney–Rivlin parameters have destabilizing effects on the pressure-driven flow of Bingham fluids.

scholarly journals Influence of Atlantic inflow on the freshwater content in the upper layer of the Arctic basin

2019 ◽  
Vol 65 (4) ◽  
pp. 363-388
Author(s):  
G. V. Alekseev ◽  
A. V. Pnyushkov ◽  
A. V. Smirnov ◽  
A. E. Vyazilova ◽  
N. I. Glok
Keyword(s):  
Fresh Water ◽  
Large Scale ◽  
Barents Sea ◽  
Lower Boundary ◽  
Arctic Basin ◽  
Water Layer ◽  
Atlantic Water ◽  
Water Masses ◽  
The Arctic ◽  
The North

Inter-decadal changes in the water layer of Atlantic origin and freshwater content (FWC) in the upper 100 m layer were traced jointly to assess the influence of inflows from the Atlantic on FWC changes based on oceanographic observations in the Arctic Basin for the 1960s – 2010s. For this assessment, we used oceanographic data collected at the Arctic and Antarctic Research Institute (AARI) and the International Arctic Research Center (IARC). The AARI data for the decades of 1960s – 1990s were obtained mainly at the North Pole drifting ice camps, in high-latitude aerial surveys in the 1970s, as well as in ship-based expeditions in the 1990s. The IARC database contains oceanographic measurements acquired using modern CTD (Conductivity – Temperature – Depth) systems starting from the 2000s. For the reconstruction of decadal fields of the depths of the upper and lower 0 °С isotherms and FWC in the 0–100 m layer in the periods with a relatively small number of observations (1970s – 1990s), we used a climatic regression method based on the conservativeness of the large-scale structure of water masses in the Arctic Basin. Decadal fields with higher data coverage were built using the DIVAnd algorithm. Both methods showed almost identical results when compared.  The results demonstrated that the upper boundary of the Atlantic water (AW) layer, identified with the depth of zero isotherm, raised everywhere by several tens of meters in 1990s – 2010s, when compared to its position before the start of warming in the 1970s. The lower boundary of the AW layer, also determined by the depth of zero isotherm, became deeper. Such displacements of the layer boundaries indicate an increase in the volume of water in the Arctic Basin coming not only through the Fram Strait, but also through the Barents Sea. As a result, the balance of water masses was disturbed and its restoration had to occur due to the reduction of the volume of the upper most dynamic freshened layer. Accordingly, the content of fresh water in this layer should decrease. Our results confirmed that FWC in the 0–100 m layer has decreased to 2 m in the Eurasian part of the Arctic Basin to the west of 180° E in the 1990s. In contrast, the FWC to the east of 180° E and closer to the shores of Alaska and the Canadian archipelago has increased. These opposite tendencies have been intensified in the 2000s and the 2010s. A spatial correlation between distributions of the FWC and the positions of the upper AW boundary over different decades confirms a close relationship between both distributions. The influence of fresh water inflow is manifested as an increase in water storage in the Canadian Basin and the Beaufort Gyre in the 1990s – 2010s. The response of water temperature changes from the tropical Atlantic to the Arctic Basin was traced, suggesting not only the influence of SST at low latitudes on changes in FWC, but indicating the distant tropical impact on Arctic processes. 

Effect of Buoyancy and Inertia on Viscoplastic Fluid-Fluid Displacement in an Eccentric Annulus With an Irregular Section: Part 2 — Displacements in Vertical Annulus

2019 ◽  
Author(s):  
Hans Joakim Skadsem ◽  
Steinar Kragset
Keyword(s):  
Drilling Fluid ◽  
Mass Density ◽  
Volumetric Flow Rate ◽  
Density Difference ◽  
Viscoplastic Fluid ◽  
Positive Density ◽  
Displacement Efficiency ◽  
Cement Slurry ◽  
Narrow Side ◽  
Vertical Annulus

Abstract Casing strings and liners are important subsurface structural components in petroleum and in geothermal wells. After the casing string has been run in hole, it is cemented to the formation by pumping a sequence of spacer fluids and cement slurry into the annulus outside the string. Spacer fluids are usually pumped ahead of the cement slurry in order to displace the drilling fluid from the annulus that is to be cemented, and thereby avoid contamination of the cement slurry. Fluid displacements are governed by inertia, buoyancy and viscosity effects, in addition to being strongly influenced by the annular geometry. Poor centralization of the casing or irregularities such as washouts can influence the displacement flows both locally and over long axial distances. We present three dimensional numerical simulations of the displacement flow involving two viscoplastic fluids in the vicinity of a symmetric local hole enlargement. We focus on laminar flow regimes in the regular part of the annulus and investigate how the volumetric flow rate and the mass density difference between the fluids affect the displacement efficiency in the regular and the irregular parts of the annulus. This study considers viscoplastic displacement flows in a near-vertical, irregular annulus and is an extension of a previous publication that focused on a near-horizontal annulus. We contextualize our simulations by comparison to industry guidelines for effective and steady laminar displacements in the regular, near-vertical annulus. Here, eccentricity favors flow in the wider sector of the annulus while a positive density difference between the fluids generates secondary, azimuthal flow toward the narrow side of the annulus. In the enlarged and irregular section, both the axial bulk velocity and casing eccentricity decrease sharply and buoyancy becomes more pronounced compared to in the regular annulus. We quantify and discuss the effects of local hole enlargements on displacement efficiencies. Simulations of cementing flows can aid in optimizing fluid properties and pump rates, including when the wellbore has suspected or confirmed zones of irregular geometries.

scholarly journals Baroclinic Instability with a Simple Model for Vertical Mixing

2019 ◽  
Vol 49 (12) ◽  
pp. 3273-3300 ◽  
Author(s):  
Matthew N. Crowe ◽  
John R. Taylor
Keyword(s):  
Growth Rate ◽  
Stability Analysis ◽  
Simple Model ◽  
Numerical Simulations ◽  
Mixed Layer ◽  
Numerical Models ◽  
Baroclinic Instability ◽  
Vertical Mixing ◽  
Small Scale ◽  
Surface Mixed Layer

AbstractHere, we examine baroclinic instability in the presence of vertical mixing in an idealized setting. Specifically, we use a simple model for vertical mixing of momentum and buoyancy and expand the buoyancy and vorticity in a series for small Rossby numbers. A flow in subinertial mixed layer (SML) balance (see the study by Young in 1994) exhibits a normal mode linear instability, which is studied here using linear stability analysis and numerical simulations. The most unstable modes grow by converting potential energy associated with the basic state into kinetic energy of the growing perturbations. However, unlike the inviscid Eady problem, the dominant energy balance is between the buoyancy flux and the energy dissipated by vertical mixing. Vertical mixing reduces the growth rate and changes the orientation of the most unstable modes with respect to the front. By comparing with numerical simulations, we find that the predicted scale of the most unstable mode matches the simulations for small Rossby numbers while the growth rate and orientation agree for a broader range of parameters. A stability analysis of a basic state in SML balance using the inviscid QG equations shows that the angle of the unstable modes is controlled by the orientation of the SML flow, while stratification associated with an advection/diffusion balance controls the size of growing perturbations for small Ekman numbers and/or large Rossby numbers. These results imply that baroclinic instability can be inhibited by small-scale turbulence when the Ekman number is sufficiently large and might explain the lack of submesoscale eddies in observations and numerical models of the ocean surface mixed layer during summer.

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