Dave Chan

Review of Sand Production Prediction Models

Sand production in oil and gas wells can occur if fluid flow exceeds a certain threshold governed by factors such as consistency of the reservoir rock, stress state and the type of completion used around the well. The amount of solids can be less than a few grams per cubic meter of reservoir fluid, posing only minor problems, or a substantial amount over a short period of time, resulting in erosion and in some cases filling and blocking of the wellbore. This paper provides a review of selected approaches and models that have been developed for sanding prediction. Most of these models are based on the continuum assumption, while a few have recently been developed based on discrete element model. Some models are only capable of assessing the conditions that lead to the onset of sanding, while others are capable of making volumetric predictions. Some models use analytical formulae, particularly those for estimating the onset of sanding while others use numerical models, particularly in calculating sanding rate. Although major improvements have been achieved in the past decade, sanding tools are still unable to predict the sand mass and the rate of sanding for all field problems in a reliable form.

A model for geotechnical analysis of flow slides and debris flows

Flow slides and debris flows incorporate a broad range of sediment-fluid mixtures that are intermediate between dry rock avalanches and hyperconcentrated flows. Following a comprehensive review of some existing analytical ap- proaches to debris flow runout analysis, a new analytical model based on energy conservation has been formulated. The new analytical model was developed to deepen the understanding of fundamental aspects in modeling of granular flows and to improve the geotechnical mobility analysis of flow slides and debris flows. The Lagrangian finite difference method was used to solve the governing equations. The model and numerical scheme have been tested against analytical solutions and experiments of granular flows with simplified geometries for sliding mass and basal topography. Results of granular flow simulations indicate that the model based on energy conservation performs well and is robust. The model can be used for geotechnical analysis of a wide range of dense granular flows, such as flow slides and debris flows.

One-dimensional compression model for tire-derived aggregate using large-scale testing apparatus

Abstract The engineering properties of tire derived aggregate (TDA) have been the subject of previous laboratory investigations; however, these investigations have been conducted primarily on TDA that is one-third the size of TDA used for engineering applications. In this study, the compression behavior of compacted TDA samples with a maximum particle size of 300 mm, typically used for engineering applications, has been investigated using custom-made testing apparatus designed to accommodate the large-sized TDA. Tire derived aggregate properties important to engineering applications, including compression behavior, the coefficient of lateral earth pressure at rest, and Poissons ratio, are provided, while variation in the gradation of TDA particles and the tire type for TDA production are experiment variables. This study also proposes a method to prepare compacted TDA samples for large-scale testing.

A study of a flowslide with significant entrainment in loess areas in China

Flowslides are a frequent type of natural disaster in loess areas and may result in the significant loss of properties and/or casualties. The Dagou flowslide is a typical event in a loess area and is accompanied by significant sediment entrainment. To analyze the mechanisms responsible for flowslides and to obtain the parameters for a runout analysis, a field investigation was conducted. Specimens were sampled on site to carry out laboratory tests, including a triaxial test, sieve analysis, and chemical component analysis. The parameters were used in the runout study employing an energy-based runout model. An analytical entrainment model was adopted to calculate the entrainment after considering physical properties and the mechanism of the entrainment process of the loess. Finally, the entrainment model was incorporated into the runout model to simulate the post-failure process of this case. Energy dissipation due to the deformation of slices was considered as it was thought to be important for a slide with a significant deformation. The simulation results were compared with the measurements, including runout distance, total volume, erosion depth, deposition height at different sections, and velocities at specific locations. The results indicate that the energy-based runout model, together with the entrainment model, can capture the kinematic characteristics of the Dagou flowslide. Therefore, it is feasible to use this model to predict the runout characteristics of flowslides in similar areas. Copyright (c) 2017 John Wiley & Sons, Ltd.

Bounding Surface Constitutive Model for Cemented Sand under Monotonic Loading

AbstractThis paper presents a critical state constitutive model for cemented sand. The model uses a single capped yield surface as a function of the void ratio, confining pressure, preconsolidation pressure, and stress ratio at the peak of the undrained effective stress path. To model the cemented materials, the formulation of the yield function, elastic moduli, plastic modulus, flow rule, and other components of the model have been modified. Having incorporated the tensile strength and cohesion, the radial-mapping formulation of the bounding surface plasticity is incorporated in the model. The modified model has been calibrated and verified based on experimental results.

A Fully Implicit Single Phase T-H-M Fracture Model for Modelling Hydraulic Fracturing in Oil Sands

Enhancing oil extraction from oil sands with a hydraulic fracturing technique has been widely used in practice. Due to the complexity of the actual process, modelling of hydraulic fracturing is far behind its application. Reproducing the effects of high pore pressure and high temperature, combined with complex stress changes in the oil sand reservoir, requires a comprehensive numerical model which is capable of simulating the fracturing phenomenon. To capture all of these aspects in the problem, three partial differential equations, i.e., equilibrium, flow, and heat transfer, should be solved simultaneously in a fully implicit (coupled) manner. A fully coupled thermo-hydro-mechanical fracture finite element model is developed to incorporate all of the above features. The model is capable of analyzing hydraulic fracture problems in axisymmetric or plane strain conditions with any desired boundary conditions, e.g., constant rate of fluid injection, pressure, temperature, and fluid flow/thermal flux. Fractures can be initiated either by excessive tensile stress or shear stress. The fracture process is simulated using a node-splitting technique. Once a fracture is formed, special fracture elements are introduced to provide in-plane transmissivity of fluid. Effectiveness of the model is evaluated by solving several examples and comparing the numerical results with analytical solutions. The model is also used to simulate large-scale laboratory hydraulic fracturing experiments.

Experimental Study on Submerged Sand Erosion through a Slot on a Defective Pipe

AbstractA physical model study was conducted to examine the development of submerged sand erosion through a slot on a defective sewer pipe. Various parameters that affect the erosion process were s...

Numerical Investigation of Sand-Bed Erosion by an Upward Water Jet

AbstractA numerical model based on computational fluid dynamics and kinetic theory of granular material is used to investigate sand-bed erosion due to an upward water jet. After verifying the numer...

A Direct Shear Apparatus With Vibrational Loading

For some geotechnical design projects where soils are exposed to dynamic loads (vibrations), it becomes necessary to evaluate the strength and deformation characteristics of the soil under existing and/or anticipated vibrations. In order to investigate the effect of the vibrations on the strength and deformation properties of soils, representative samples should be collected and tested in laboratories and subjected to vibration of expected magnitudes. In this case, it is important that the laboratory equipment used is able to simulate field conditions as close as possible to provide the necessary parameters that can successfully be used in the design. A vibrational direct shear apparatus has been developed based on the conventional direct shear apparatus to evaluate the strength and deformation characteristics of soils (granular and cohesive) under a wide range of vibrational accelerations and frequencies. The apparatus makes it possible to test soils in both stress and displacement controlled modes. The design of the apparatus is such that it allows modification of the most commonly used direct shear apparatuses into the vibrational ones. The new apparatus was built and tested to prove its performance and reliability.

Constitutive model for cyclic behaviour of cohesionless sands

ABSTRACT This paper presents a constitutive model for describing the stress-strain response of sands under cyclic loading. The model, formulated using the critical state theory within the bounding surface plasticity framework, is an upgraded version of an existing model developed for monotonic behaviour of cohesionless sands. With modification of the hardening law, plastic volumetric strain increment and unloading plastic modulus, the original model was modified to simulate cyclic loading. The proposed model was validated against triaxial cyclic loading tests for Fuji River sand, Toyoura sand and Nigata sand. Comparison between the measured and predicted results suggests that the proposed modified model can capture the main features of cohesionless sands under drained and undrained cyclic loading.