3D computer simulations and experiments are employed to study random packings of compressible spherical grains under external confining stress. In the rigid ball limit, we find a continuous transition in which the stress vanishes as (straight phi-straight phi(c))(beta), where straight phi is the (solid phase) volume density. The value of straight phi(c) depends on whether the grains interact via only normal forces (giving rise to random close packings) or by a combination of normal and friction generated transverse forces (producing random loose packings). In both cases, near the transition, the system's response is controlled by localized force chains.

Packings of Compressible Granular Materials

Effect of proppant addition schedule on the proppant distribution in a straight fracture for slickwater treatment

Updated criterion to select particle size distribution of lost circulation materials for an effective fracture sealing

Since the beginning of the US shale gas revolution in 2005, the development of unconventional oil and gas resources has gathered tremendous pace around the world. This book provides a comprehensive overview of the key geologic, geophysical, and engineering principles that govern the development of unconventional reservoirs. The book begins with a detailed characterization of unconventional reservoir rocks: their composition and microstructure, mechanical properties, and the processes controlling fault slip and fluid flow. A discussion of geomechanical principles follows, including the state of stress, pore pressure, and the importance of fractures and faults. After reviewing the fundamentals of horizontal drilling, multi-stage hydraulic fracturing, and stimulation of slip on pre-existing faults, the key factors impacting hydrocarbon production are explored. The final chapters cover environmental impacts and how to mitigate hazards associated with induced seismicity. This text provides an essential overview for students, researchers, and industry professionals interested in unconventional reservoirs.

Unconventional Reservoir Geomechanics: Shale Gas, Tight Oil, and Induced Seismicity

In this, the twentieth Campbell Memorial lecture, I propose to discuss that aspect of metallurgy which has come to be known as mechanical metallurgy. This kind of metallurgy comprises our efforts to understand the relationships among the measured mechanical properties of metals and their mechanical behavior in service, and to understand the way in which these mechanical properties and service characteristics are controlled by chemical composition and structure. This field was not one which received a large amount of consideration from Professor Campbell, but I am sure that if he were alive today it would command his attention. In his day, the factors that influence the structure of alloys engaged the talents of some of the best men, and Professor Campbell and his contemporaries nobly inaugurated the work which has given us such a complete understanding of how to control the structure of metals, that many of us now feel free to turn to other problems. Of course this does not mean that no problems in that field remain to be solved. Rather, progress there has been so great that it now seems profitable to turn to other fields. I have chosen to concentrate on the problem of trying to understand quantitatively how alloying elements in solid solution, and undissolved compounds distributed in these solid solutions, affect mechanical properties. Broadly there are two aspects to what we mean by mechanical properties. These are succinctly called strength and ductility. By strength we mean the resistance of a substance to distortion or fracture, and by ductility we mean how much we may distort it before it fractures. There are many ways to measure these. I have chosen to concentrate on the simple tension test, for I believe it yields as much or more information than any other test. Indentation hardness, which has been widely used, yields much less information, and those who have used it only have missed much of interest. Even the tension test alone is inadequate to complete understanding, but by and large other tests are useful to supplement what the tension test can tell us. This applies particularly to measurements of strength, for which the tension test is almost wholly adequate; but it does not apply so well to ductility, where the conditions of loading are much more important and much less well understood in their action. There are two aspects to what we mean by strength. These are, first, resistance to flow, and second, resistance to fracture [1]. Both are functions of numerous variables, and can only be plotted on two-dimensional space by ignoring or holding constant all the variables but one. Both must be thought of as surfaces in multi-dimensional space. Among the variables which may influence both the flow and fracture stress, aside from composition and structure which are our principal concern today, we may list strain, time rate of straining, and temperature as the ones that most commonly are taken into consideration. In Fig. 1, the resistance to flow and the resistance to fracture are plotted against strain. I like to refer to these two curves simply as the flow curve and the fracture curve, for the effect of deformation on Reprinted from Transactions of the American Society for Metals, 36, 30–60 (1946). Copyright 1946 by the American Society for Metals, Cleveland, Ohio.

Strength and Ductility

Coupled CFD-DEM simulation of hydrodynamic bridging at constrictions

Proppant Distribution Among Multiple Perforation Clusters in Plug-and-Perforate Stages

Effect of Perforation Geometry and Orientation on Proppant Placement in Perforation Clusters in a Horizontal Well

Proppant Distribution Among Multiple Perforation Clusters in a Horizontal Wellbore

\n Proppant placement plays a crucial role in ensuring that the conductivity of fractures is maintained after a hydraulic-fracturing treatment. The process involves the transport of suspended solids in a liquid, usually a water-based fluid, from the wellbore through perforations and finally into fractures. Many studies have focused on proppant settling and transport in fractures, but relatively few studies have investigated the proppant transport process in a wellbore through perforations. This paper addresses the important issue of proppant transport through perforations using a novel numerical technique. The objective is to evaluate the efficiency of proppant transport in a perforated horizontal well under different suspension flow conditions.\n In this paper, proppant transport through a perforated horizontal casing is modeled using a coupling of computational fluid dynamics and the discrete element method (CFD-DEM). Reasonable agreements are found between the modeling results and published experimental data. Furthermore, the effectiveness of proppant transport through a perforation is evaluated by the particle transport efficiency (Ei), which is defined as the mass fraction of particles transported through a perforation relative to the total mass of particles in the wellbore upstream of the perforation. The effects of casing diameter, proppant size, proppant density, proppant concentration, fluid-flow rate, fluid rheology, perforation size, and perforation orientation on Ei are investigated.\n The simulation results show that proppant inertia strongly influences proppant transport into a perforation. The proportion of proppant that goes into a perforation is typically much different than the proportion of fluid that goes into the same perforation. This results in an increase in the proppant concentration in the slurry as the slurry flows from the heel to the toe side of a plug-and-perforate stage. Results and models presented in this paper provide directions to quantify and potentially control proppant distribution in perforation clusters in horizontal wells.

Chu-Hsiang Wu

Papers

Coupled CFD-DEM simulation of hydrodynamic bridging at constrictions

Proppant Distribution Among Multiple Perforation Clusters in Plug-and-Perforate Stages

Effect of Perforation Geometry and Orientation on Proppant Placement in Perforation Clusters in a Horizontal Well

Proppant Distribution Among Multiple Perforation Clusters in a Horizontal Wellbore

Modeling Proppant Transport Through Perforations in a Horizontal Wellbore