Transport Of Sand Particles Research Articles

Acoustic seabed classification using QTC IMPACT on single-beam echo sounder data from the Norwegian Channel, northern North Sea

Sediment mapping is important for understanding the physical processes, the impact of human activity, and the conditions for marine life on the seabed. For this purpose, the seabed classification tool QTC IMPACT analyses statistical variations in single-beam echo sounder data. QTC was applied in a large and physically diverse area of the Norwegian Channel, between 59°30′N and 61°N, to produce a new sediment map and to verify the QTC algorithm. The results were interpreted using ground truth (grain size analyses of 40 gravity cores and five grab samples), multi-beam echo sounder bathymetry (MBES), and seismo-acoustic profiles. Surficial sediments were divided into five classes: (1) mud and silt, (2) a variety of clay, silt and sand, (3) sandy mud with gravel, (4) sand with gravel, and (5) clay and sandy clay. Along the Norwegian coast, where MBES imagery shows evidence of glacial erosion, the surficial sediment distribution is variable. The echo shape analysis of QTC did not produce a natural partition of the data, and statistical assumptions did not always hold. Sediment classification was therefore sensitive to the choice of cluster algorithm. However, QTC produced the most physically plausible results on a large scale compared to other cluster algorithms. Class boundaries were consistent with supporting data. One exception is a transition from muddy to sandy sediments not visible in seismo-acoustic data. A possible explanation is that seabed fluid seepage and water current erosion cause sand particle transport into the western part of the channel. The study confirms the capability of QTC in a complex environment, but there are some possible improvements.

Experimental and theoretical study of the trajectories of saltating sand particles over desert areas

Transport of sand particles over desert areas in the lower saltation layer is studied experimentally and theoretically. The trajectories of saltating sand particles are reconstructed by means of high-speed video recording. An instantaneous concentration profile of saltating sand in a layer from 0 to 40 mm is presented. A numerical model of sand particle movement in the surface air layer is developed. The influence of the model parameters on the saltating sand trajectories is analyzed. A method for solution of the inverse problem of saltating sand dynamics is proposed. The reconstruction of dynamic parameters of the problem from saltating sand trajectories is presented. It is found that some turbulent parameters can be estimated from the trajectory measurement data.

A Comprehensive Study of Sanding Rate From a Gas Field: From Reservoir to Completion, Production, and Surface Facilities

Summary An offshore gas field has been producing sand for a few years. Sand production has been closely monitored through acoustic flowline devices and a sand-collection system installed on the platforms. Observation of sand production has triggered evaluation of whether to install surface desanders or to complete future wells with downhole sand control. This evaluation requires a prediction of sanding rate over the reservoir life. The possibility of providing downhole sand control on existing wells was also evaluated in separate studies. Predicting sanding rate, particularly for gas fields, has been historically challenging, mainly because of the sporadic nature of sand production, inadequate quantification of fundamental physics, and lack of representative laboratory tests and reliable field calibration. To tackle these challenges, four studies have been designed and executed: (1) the development of a reliable log-based rock-strength estimate, (2) the prediction of sanding rate over the reservoir life for a conservative well condition, (3) the evaluation of sand-particle transport from the reservoir to the surface facilities, and (4) the estimate of potential erosion of platform facilities. The sanding-rate prediction is based on extensive laboratory tests of four carefully selected whole cores with gas and water flow. It then has been validated by field-monitoring data from an acoustic flowline device on each producer and a sand-collection system on the platforms. The studies have provided a prediction of (1) future sand production, (2) how much of the produced sand will be seen at the surface (and, therefore, how much of it will fall into the rathole), (3) how fast various components of the surface facility will erode over the field life, and (4) what will be the optimal completion strategy for sand control should it become necessary. They have provided input to an integrated evaluation of completion design, reservoir management, platform configuration, and field economics.

Dynamics and Numerical Modeling of Sandy Desert Morphology Caused by Aeolian Transport of Sand Particles

Wind caused the much sediment fluxes leading to both erosion and deposits in the sandy desertification area, and the much kind of beautiful sandy desert morphologies are formed. This is really crucial to the development of the dynamic behaviour of aeolian transport of sand particles. The sand desert morphologies are representing significant information archives for understanding the desertification problem. Dynamics and numerical modeling provides an essential tool for studying the aeolian transport of sand particle and morphology of sand desert such as ripple and dune. In this study, the mathematical models based on the dynamics are analyzed by considering the several keys as saltation, creep, suspension, avalanche and its threshold condition etc. for sand morphology forming processes. Then due to sand flow field real characteristics, the establishing process of stream flow field are analyzed, and the implication relationships as well as the coupling process between uniform stream flow field and the sand flow field are analyzed. Finally, the sand flow field models is discretized, and different kinds of sandy desert morphology are simulated by considering the sand particle size and mass in fixed, semi-fixed and free sand flow field area.

The transport of particles at low loading in near-horizontal pipes by intermittent flow

The transport of sand particles at low concentration in horizontal and near horizontal pipes in air/water slug flow has been studied. Low concentration means less than 1 in 1000 by volume, a level of concentration of interest in the transport of sand by oil and gas in subsea flowlines (Stevenson & Thorpe, Proceedings of the Ninth International Conference on Multiphase Flow, Cannes, France, 1999) but much lower than the range of interest in all previous work on hydraulic conveying which may be thought to be a related field of study. The velocity of sands of sieving diameter of 1.1 and 0.51 mm have been measured for various gas and liquid flowrates and in liquids of viscosity in the range 1.0– 7.1 mPa s in two 12 m long pipes of internal diameter 40 and 70 mm . Video recordings have been analysed to determine the mechanisms involved in transport of particles in slug flow and are used to explain the observed decrease in particle propagation velocity with increased liquid viscosity. There being no totally satisfactory mechanistic model for intermittent flow in the literature, a semi-theoretical model for sand transport is not currently facilitated. Therefore the approach taken is that of dimensional analysis. Particle velocity, V P , is successfully correlated using dimensionless groups which include liquid viscosity, particle size and liquid and gas flow rates. The preferred correlation for sand in liquids of viscosity less than about 5 mPa s is V P j f =0.95 1+ j g j f − 1.38 j g j f +0.88 Fr f Re f Fr f d D 1.5 −0.180. All the parameters, except gravitational acceleration, have been varied in the experimental programme. It is found that particle velocity, V P is independent of pipe inclination in slug flow for pipe inclinations of up to three degrees. The above correlation is used to produce an equation that predicts the point of incipient-sand deposition. This equation can be used to estimate the maximum turndown of two-phase offshore oil production from satellite wells before sand will begin to deposit at the bottom of the pipe.

Sand Deposition Inside a Horizontal Well-A Simulation Approach

Abstract Horizontal wells have been shown to be successful in improving oil recovery for marginal heavy oil reservoirs in Saskatchewan and Alberta. One commonly encountered problem in recovery operations for these poorly consolidated reservoirs is the production of sand and fines into the horizontal wellbore, where they settle and accumulate. This paper reports the numerical modeling of gravitational deposition of sand in a horizontal well in such heavy oil reservoirs. The numerical model described in this work examines the transport process mechanistically, based on the conservation equations for the fluid phase (heavy oil) and the solid phase (sand particles). The interaction between these phases is described by empirical correlations. The equations are solved numerically to determine the concentration of sand particles and oil, and their respective pressure and velocity distributions inside the horizontal well. According to the simulation results, oil viscosity and particle size play important roles in the transport process, including controlling the gravitational settling tendency of solid particles inside the horizontal wellbore. The results provide insight into the roles different mechanisms affect the transport of sand particles; as such, they provide guidelines for production operations involving horizontal wells in poorly consolidated and unconsolidated reservoirs. Introduction The use of horizontal wells, in Saskatchewan and Alberta heavy oil reservoirs underlain with bottom-water, has been found to improve primary recovery performance prior to water coning-recovering up to 15%, in some cases, of the initial oil in place, compared with only 5% for a vertical well(1). Horizontal wells have also been successfully used for increasing steamflood recovery(2,3). Due to the unconsolidated or poorly consolidated nature of these reservoirs, solid (sand and fines) production is quite prevalent. The produced solids lead to several production problems, including sand filling up the wellbore, preventing the operation of downhole pumps and surface equipment, etc.(4) In horizontal well cases, sand production potentially poses a serious problem, as the sand could settle and accumulate inside the horizontal wellbore. This settlement and accumulation of sand particles could give rise to reduced cross-sectional areas of the wellbore open to flow. The study reported in this paper examines, using numerical simulation, the gravitational deposition of sand particles inside a horizontal wellbore. A brief survey of the relevant literature is given in the following. Solid-liquid multiphase flows are usually very complex, due to the large number of variables involved in the transport processes, and typically poorly understood interaction between the variables. There have been many experimental investigations of these (and other) flow processes, particularly focused on the deposition of the solid particles. Many of the earliest investigations of solid liquid flows focused on the settling tendency of solid particles. Richardson and Zaki(5) experimentally determined that the falling velocity of a suspension relative to a horizontal plane was equal to the upward velocity of the fluid required to maintain a suspension at the same concentration. For different flow regimes (i.e., Reynolds numbers), separate correlations were developed (from experimental data) for the exponent which corresponds to the slope of log-log plot straight lines between suspension falling velocities and suspension porosities.

X線TV透視装置による粒状体地盤-流体系の動的相互作用の可視化実験法について

The technique of X-ray TV visualization is described in this study as applied to seepage failure experiments of a sand and gravel two-layer system. This technique allows for the precise visualization of the microscopic internal deformation processes, the dynamic development of a liquefaction front in a sand layer, the transport of sand particles into a gravel layer, the failure mode of a whole system and so on. This experimental technique provides a powerful and promising tool for understanding the dynamic interaction mechanisms of granular media/pore fluid systems.

FLYING SNAILS—HOW FAR CAN TRUNCATELLINA (PULMONATA: VERTIGINIDAE) BE BLOWN OVER THE SEA?

With populations of land snails of very small size like Vertiginidae, questions have arisen as to whether populations of relatively distant islands in archipelagos are really isolated from each other. Apart from other flight agencies, airborne transport of loose specimens is not improbable in stormy weather conditions. Currently, mechanisms of wind-borne transport of sand particles over short and long distances have been intensively studied. The results are available in the literature on sediments, allowing the calculation of probable flight distances for particles in suspension. For living snails of the Aegean species Truncatellina rothi, an average fall velocity of 2.6-2.7 m s1 has been determined in experiments under laboratory conditions. Applying these results, Truncatellina living on an island at 100 m altitude and close to the coast could be transported up to several kilometers in heavy storms, which are not uncommon in the Aegean archipelago (Greece). This would imply that many of the Aegean islands are not effectively isolated for minute snail species, and that genetic interchange between island populations is probably frequent.

Correction to “System of numeric models for sand particle transport by wind” by Long Li and Lawrence W. Martz

Correction to “System of numeric models for sand particle transport by wind” by Long Li and Lawrence W. Martz

System of numeric models for sand particle transport by wind

A system of experimental and mathematical models was developed from data on grain particle transport, collected from a series of experiments in a large‐scale wind tunnel, and from mathematical principles. The experimental model was derived from a FORTRAN program using the observed data. As a first attempt, it took into account the role played by the following factors in grain particle transport: the grain‐size distribution, the mean diameter of the particle size class, die mean diameter of the effective surface particles, the surface mobility, friction velocity, and threshold velocity. The comparison between the observed and the predicted results indicated that the experimental model was able to predict the transport rate of grain particles in different size classes over time with good reliability. The mathematical models used in conjunction with the experimental model could be employed to calculate the variation of the mean grain size, the grain‐size distribution, the approximate fluid threshold velocity, and the accumulated erosion of the particle surface over time. The experimental model should be applied with caution to natural conditions because of the assumption of a dry, loose, and large‐roughness‐free surface and aerodynamically dominant fluid. The mathematical models, except for fluid threshold velocity, were accurate, given a precise transport rate of grain particles in different size classes over time.

Sand mass density and borrow material compatibility for beach nourishment

Design of successful and cost-effective beach nourishment schemes requires a sound understanding of the hydraulic character of both borrow material and native beach sand. Techniques for assessing borrow material compatibility exist, but have proven inadequate in some situations. Most methods use a particle size parameter to represent sand transportability, although hydraulic theory and the nature of post-erosional lag deposits on Durban beaches suggest that mass density may also be a factor of importance. Results of a flume test on natural and artificialy constituted samples of Durban beach sand showed that transport of sand particles was unrelated to median particle size, but inversely correlated with sample mass density. The study concludes that where beaches consist of mineralogically heterogeneous material, a density factor should be included in any attempt to assess sediment transport rates and borrow material compatibility.

Sand Particle Transport in Perforated Casing

From the study reported here it was concluded that the sand-transporting efficiency of water increases (at a diminishing rate) with an increase in flow rate, but varies inversely with solids concentration and particle size over a wide range of flow rates. It was also concluded that transport efficiency is probably not affected by perforation pattern alone. Introduction The topic of formation sand control is known by all petroleum engineers, and the problems associated petroleum engineers, and the problems associated with the production of sand in oil, gas, and water wells have been studied extensively. Examples of approaches to these problems include work concerning the arching behavior of sand grains, consolidating chemicals, combustion techniques, and soil mechanics theory.An important aspect of sand control that has received inconsistent study is sand prepack operations, in which mixtures of sand and liquid are pumped down the well. Often, these sand grains must be transported through casing perforations (Fig. 1). Although the art of sand prepacking is a matter of routine in many oilfield operations, knowledge is scarce concerning the behavior of these sand grains in the fluid stream as they approach casing perforations. One reason for this scarcity of knowledge is that it is extremely difficult to apply a mathematical approach in expressing the behavior of solid particles in a liquid. The added difficulty of expressing fluid turbulence and the physical configuration of casing and perforations by mathematical models makes it almost perforations by mathematical models makes it almost impossible to completely solve the problem unless many simplifying assumptions are made. Particle trajectory studies have been made under these simplified conditions, but the results cannot be conveniently applied to specific down-hole configurations as encountered in petroleum operations. Experimental techniques may eliminate most of the problems associated with analytical treatment; but to simulate the field operation in a realistic manner, a considerable investment in laboratory equipment is required. Experimental techniques were deemed to have more direct application to this investigation, and were designed to minimize scale-up factors when applied to sand-pack operations. Basic Considerations The problem of determining whether a sand particle will be transported by the carrier fluid into the perforation or whether it will settle below the perforation or whether it will settle below the perforation essentially depends on the relative magnitudes of perforation essentially depends on the relative magnitudes of particle inertia and fluid drag. The inertia of the sand particle inertia and fluid drag. The inertia of the sand particle causes it to resist following the fluid paths particle causes it to resist following the fluid paths into the perforation. Fluid drag, however, tends to move the particle in the direction of flow. The shape of the particle and the turbulence level of the fluid determines the extent of extraneous particle movement along the primary direction of travel.Two extremes of particle transport are obvious by intuition:1. No sand particles are transported into the perforations at zero flow rate, since the fluid is not perforations at zero flow rate, since the fluid is not directed toward the perforations, and drag forces in the horizontal direction are zero.2. Nearly all particles are transported when the viscosity and flow rate are sufficiently high to prevent particle settling. High viscosity and high flow rate particle settling. High viscosity and high flow rate maximize the fluid drag and minimize particle inertia. JPT P. 80

港灣の深さに及ぼす主風の影響に關する研究(第五報)

In the present paper, is made a theoretical discussion, based on W. Ekman's theory of drift current, on the direction of the general current near the bottom of shallow seas or bays produced by prevailing winds.Two special cases were fully discussed, viz.(I) The case of an enclosed sea of uniform depth, d'.Considering that a steady wind is blowing everywhere with the same strength horizontally along the positive direction of y-axis, the x- and y-components of the current produced thereby were formulated.The direction of the bottom current upon which the transport of sand particles on the bottom of the sea chiefly depends, is given by the expression tgα=A/B, in whichwhere α is the angle between the direction in which the prevailing wind is blowing and that of the bottom current, measured clockwise starting from the former to the latter, T is the tangential stress of the wind, D' is the depth of frictional _??_nfluence, a=π/D', γx and γy are the slope angles of the sea-surface in the directions of x and y respectively, ρ is the density of sea water, g the acceleration due to gravity.α was computed for va_??_ious values of depth, d', and it was found that α gradually increases with the depth, d', but that it does not exceed 45° so long as d' does not exceed the depth of frictional influence. Thus, it follows that the mathematical expression representing the effect of prevailing winds may be written in the form F (γ) cos (θ-θ0+α). Since, however, α is small and negligible if d' does not exceed half the depth of frictional influence, we may use the expression F (γ) cos (θ-θ0) introduced before by the present author, instead of F (γ) cos (θ-θ0+α), for most practical purposes at least for the first approximation.(II) The case of a sea of uniform depth, d', with a straight coast.Considering that a steady and uniform wind is blowing horizontally along the positive direction of y-axis, the x- and y- components of the current produced thereby were formulated.The direction of the bottom current was found to be given by the expression tg (2π-β)=A/B, in whichwhere β is the angle between the direction in which the wind is blowing and that of the bottom current, measured counterclockwise starting from the former to the latter.β was computed for various values of d' and θ-θ0, θ-θ0 being the angle between the direction of the prevailing winds and that of the coast line.Thus, the mathematical expression representing the effect of prevailing winds may be written in the form F (γ) cos (θ-θ0+π-β). Since, however, as in the case (I), (π-β) is not large if the depth of the sea is shallow and it is almost negligible if d' is less than half the depth of frictional influence, the value of F (γ) cos (θ-θ0+π-β) does not much differ from that of F (γ) cos (θ-θ0), and we may use the latter expression for practical purposes at least for the first approximation.It was further suggested that the above theory may be applied to some extent to the case of a peninsula. Some actual examples which seem to justify the above theory were found.A more detailed discussion will appear in a future number of the “Geophysical Magazine.”