Analysis of a more realistic well representation during secondary recovery in 3-D continuum models

The effectiveness of secondary recovery methods in reservoir development studies depends on the knowledge about how fluid-carrying regions (i.e. good-quality rock types) are connected between injection and production wells. To estimate reservoir performance uncertainty, comprehensive simulations on many reservoir model realisations are necessary, which is very CPU consuming and time demanding. Alternatively, we can use much simpler and physically based methods such as percolation approach. Classic percolation assumes connectivity between opposite 2-D faces of a 3-D system; whereas, hydrocarbon production is achieved through active wells that are one-dimensional lines (e.g. vertical, horizontal or deviated wells). The main contribution of this study is to analyse the percolation properties of 3-D continuum percolation models with more realistic well representations during secondary recovery. In particular, the connection of randomly distributed sands (i.e. good-quality rock types) between two lines (representing two wells) located at two corners of the system are modelled by Monte Carlo simulations. Subsequently, the connectivity and conductivity of such a line-to-line well representation is compared with that of face-to-face well representations in the previously published results. The critical percolation properties of those systems as well as the universality concept are also investigated. As there are many rooms for connections in 3-D models, we found that the principal percolation properties will not be altered significantly when the problem with a face-to-face connection is transformed to a line-to-line connection model.     

A rational and realistic rock mass modelling strategy for the stability analysis of blocky rock mass

Due to the importance of a realistic rock mass model for the achievement of accurate and reliable results from numerical analysis of blocky rock mass, a probability based rock mass geometrical model is proposed in the present study. The rock mass geometry is built based on site investigation data and stochastic analysis of the discontinuity mapping results. The discontinuities and/or sets of them, either finite or infinite in size, planar or non-planar, convex or concave in shape, can be implemented in the three-dimensional rock mass model. Key block analysis and support design are then suggested to the stochastic rock mass models. To achieve a realistic stability analysis of the rock mass with the proposed probabilistic rock mass model, a few suggestions have also been made. These include the adoption of realistic constitutive models to intact rock and rock discontinuities, use of numerical model to technically handle numerical difficulties and development of a realistic modelling strategy to achieve realistic and affordable computational cost, etc.     

Toward a general procedure for analysis of extreme random events in the earth sciences

Engineering and scientific approaches to design magnitude estimation are briefly revisited. Some defense is offered for use of annual maxima in design as if they were variables from a common distribution. However, to assume any particular form of distribution tail beyond the largest data value is not justifiable, regardless of the degree of data support over the main body of the distribution. An alternative approach to the design problem is suggested through use of parameter-free nonparametric estimation using the kernel method. Some simulation results are presented which suggest that the parameter-free approach is worthy of further development. A particular advantage of nonparametric methods is that competing estimators can be checked against parametric distributions, leading to a progressive improvement in estimator accuracy.This paper was presented (by title) at Engineering Concepts, MGUS-87 Conference, Redwood City, California, 13–15 April 1987.     

Statistical analysis of some main geomechanical formulations evaluated with the Kaniadakis exponential law

The following paper reviews four well-known geomechanical equations, i.e. the elastic modulus of the rock mass as function of the Rock Mass Rating (RMR) system, the relation between Rock Quality Designation (RQD) and spacing distribution of the natural discontinuities in the rock mass, the distribution of the discontinuity spacing along a straight line for a rock mass and the intact rock strength in function of the specimen diameter by using a power-law flat tails equation based on the theory of Kaniadakis. The results show that by using novel formulations, the experimental data are better approximated by the power-law flat tails statistical approach, which shows a trend similar to ordinary exponential for a certain part of the interval of variability of x; the tails, however, follow the power law for extreme values of x. It was, therefore, possible to obtain new formulations able to better represent some fundamental aspects of geomechanics.     

Nonlinear porodynamic analysis by adaptive semi-explicit/explicit time marching formulations

Acta Geotechnica - In this paper, we propose two adaptive semi-explicit/explicit numerical approaches to analyse nonlinear porodynamic models. In this context, simple, stabilised, non-iterative,...     

Sediment yield estimation formulations for arid regions

Previous studies lack proper and quick assessment of sediment yield rates in arid regions. Sediment yield at a point along the main channel of a drainage basin is an integrated result of upland, gully, and channel erosion, transportation, and depositional processes. The external dynamic agents of sediment yield are water, wind, gravity, temperature change, ice, and biological activities. Although each may be important in arid regions, at locations, occasionally present-day hydrological cycle works water are the most widespread agent of erosion and account for the bulk of sediment yield. This paper focuses on sediment yield formulations in arid regions in terms of little morphology in addition to the runoff discharge after a storm rainfall. Among the morphological variables are the drainage basin area, main channel slope, and the drainage density. Hence, the channel head is represented by the combination of drainage area and the slope. The emphasis is given to the determination of simple and straightforward sediment yield rate formulations by dimensional analysis technique. Three simple formulations are derived, and two of them are applied to one of the largest wadis, Wadi Baysh, with its 54 sub-basins, in the southwestern Saudi Arabia.     

Comparison of numerical formulations for the modeling of tensile loaded suction buckets

The tensile resistance of a suction bucket is investigated using three different numerical formulations. The first formulation utilizes the three-field u-p-U formulation accounting for solid and fluid displacements, u and U, as well as the pore-fluid pressure, p. The two other formulations comprise the simpler u-p formulation in its dynamic and quasi-static form, accounting only for solid displacement and pore-fluid pressure. As basis for comparison, the tensile resistance of a single suction bucket is investigated using a velocity-driven model for a wide range of velocities. It is found, that the quasi-static u-p formulation is sufficient for most relevant velocities.     

Toward the definition of criteria for the recognition of artificial bone alterations

Cutting, fracturing, flaking, and polishing of bones and other osseous materials may in some instances be interpreted as evidence of former human activity. Such interpretations must avoid confusion with the wide variety of natural processes that alter bones. Reliable criteria are prerequisite to sound inferences based on bone, regardless of whether they have been redeposited or recovered from primary assemblages. Criteria must be defined by means of actualistic studies (neotaphonomy) and experiments that demonstrate causal relationships between patterns of alteration and the processes that produce them. The criteria can be empoyed in the interpretation of fossil bones (paleotaphonomy) on the basis of uniformitarian principles. At the present time, such relationships are relatively well understood in the case of cut marks on bones, and modest progress has been made in investigating fractured and flaked bones. Polished bones are little understood and difficult to interpret.     

Toward a model for airflow on the lee side of aeolian dunes

The interaction between dunes and the primary wind results in a complex pattern of secondary airflow on the lee side of dunes. From 15 dunes studied during transverse flow conditions at Padre Island in Texas, White Sands in New Mexico, and the Algodones in California, distinct flow regions can generally be recognized, with the overall flow structure comparing favourably to that proposed for subaqueous bedforms. Downwind of dunes with flow separation is a back-flow eddy that extends about four dune-brink heights downwind from the brink of the dune. Beyond the separation cell, the velocity profiles can be divided into regions based upon segments separated by ‘kinks’ in the velocity profiles. The interior is an area above the dunes of relative high wind speed but low velocity gradient. Beneath the interior is the wake, which consists of two layers. The upper wake exhibits an uppermost portion where the flow decelerates while the remainder exhibits accelerating flow, so that the overall velocity gradient decreases downwind. The lower wake exhibits low velocity gradients and wind speeds that accelerate downwind at all heights, but primarily near the top of the layer, thereby causing the velocity gradient to increase downwind. At about eight dune heights downwind, the upper and lower wakes equilibrate to a single profile with the kink between them no longer apparent. The lowest recognizable region is the internal boundary layer. It is recognized by a relatively steep velocity gradient below the wake, and never exceeds a few tens of centimetres in height for our data set. Because of acceleration and increasing shear stress within this layer, interdune flats are at least potentially erosional. Overall, the wake and internal boundary layer show a downward transfer of momentum from upper regions so that the flow recovers. Where flow separation does not occur, simple flow expansion down the lee-face causes flow deceleration.     

Toward predicting blast-induced flyrock: a hybrid dimensional analysis fuzzy inference system

A hybrid dimensional analysis fuzzy inference system approach was introduced to predict blast-induced flyrock in surface mining, by integrating a dimensional analysis procedure and Mamdani’s fuzzy inference system. In the dimensional analysis, the blast-induced flyrock was considered as a function of the most effective parameters. Hence, a number of dimensionless products resulted and were used as input and output parameters of Mamdani’s fuzzy inference system. The capability of the hybrid approach was determined by comparing its results with the real measurement of flyrock in the case of a copper mine, based on a number of 320 in situ blasting datasets. Predictions by the system were close to the real measurements. Sensitivity analysis of the hybrid dimensional analysis fuzzy inference system showed that the most effective dimensionless products on flyrock distance were spacing, the multiplication of rock mass rating and hole length, and the subtraction of burden and hole length multiplication and stemming length.     

将我国深海大洋研究推向新阶段

1998年春,我国正式参加大洋钻探国际合作计划(ODP),成为大洋钻探计划的第一个“参与成员”(associatemember),迄今正好5周年,这是令我难忘的5年。1999年2月6日～4月12日,在汪品先院士和WarrenPrell两位首席科学家的共同主持下,在我国南海实施了大洋钻探184航次(ODPLeg184),使我国真正从学术上进入深海研究的国际行列。在那个航次的28位上船科学家中有9位中国人,这是自1968年实施深海钻探计划(DSDP,ODP的前身)的第一次,使我感到特别振奋。ODP184航次及其随后的实验室研究,取得的学术成就包括:(1)建立起西太平洋区近3000万年来最…     

A statistical comparison of various source formulations for explosions and earthquakes

Stochastic models are derived for two source formulations for explosions. Using this kind of model, a comparison is made between source time functions due to Blake, Haskell, Mueller and Murphy, and Von Seggern and Blandford, for explosions, and between -square (Aki, Brune)and -cube (Aki, Haskell)models for earthquakes. When seeking a stochastic model for records of Rayleigh waves from atmospheric explosions, the k-model corresponding to Haskell's time function was found to be an appropriate choice.     

Towards realistic simulations of lava dome growth using the level set method

The level set method has been implemented in a computational volcanology context. New techniques are presented to solve the advection equation and the reinitialisation equation. These techniques are based upon an algorithm developed in the finite difference context, but are modified to take advantage of the robustness of the finite element method. The resulting algorithm is tested on a well documented Rayleigh–Taylor instability benchmark [19], and on an axisymmetric problem where the analytical solution is known. Finally, the algorithm is applied to a basic study of lava dome growth.     

Toward exploratory analysis of diversity unified across fields of study: an information visualization approach

The study of the diversity of multivariate objects shares common characteristics and goals across disciplines, including ecology and organizational management. Nevertheless, subject-matter experts have adopted somewhat separate diversity concepts and analysis techniques, limiting the potential for sharing and comparing across disciplines. Moreover, while large and complex diversity data may benefit from exploratory data analysis, most of the existing techniques emphasize confirmatory analysis based on statistical metrics and models. This work aims to bridge these gaps. First, by cross comparing the analyses of species diversity, microbial diversity, and workgroup diversity, we introduce a framework of diversity concerns aligned across the three areas. The alignment framework is validated and refined by feedback from subject-matter experts. Then, guided by the framework and theoretical information visualization and visual analytics principles (as distinguished from scientific visualization), we propose a unified taxonomy of common analytical tasks for exploration of diversity.     

Finite element analysis of land subsidence above depleted reservoirs with pore pressure gradient and total stress formulations

The solution of the poroelastic equations for predicting land subsidence above productive gas/oil fields may be addressed by the principle of virtual works using either the effective intergranular stress, with the pore pressure gradient regarded as a distributed body force, or the total stress incorporating the pore pressure. In the finite element (FE) method both approaches prove equivalent at the global assembled level. However, at the element level apparently the equivalence does not hold, and the strength source related to the pore pressure seems to generate different local forces on the element nodes. The two formulations are briefly reviewed and discussed for triangular and tetrahedral finite elements. They are shown to yield different results at the global level as well in a three‐dimensional axisymmetric porous medium if the FE integration is performed using the average element‐wise radius. A modification to both formulations is suggested which allows to correctly solve the problem of a finite reservoir with an infinite pressure gradient, i.e. with a pore pressure discontinuity on its boundary. Copyright © 2001 John Wiley & Sons, Ltd.     

Roughing and cleaning flotation behaviour and the realistic simulation of complete plant performance

Data are presented which illustrate a range of flotation behaviour observed for roughing and cleaning operations in industrial plants. Differences are observed in the size by size recoveries in cleaner flotation from those measured in the roughers.The implications of these differences to flotation modelling are discussed, and the importance of conducting confirmatory laboratory batch flotation tests is emphasized.Batch flotation tests have indicated that for certain minerals the flotation characteristics in the cleaner tests are substantially different from those in rougher tests conducted under the same conditions of pulp level, impeller speed, aeration rate and froth removal. The differences are most pronounced for the coarse particles.Computer simulations of a rougher-cleaner circuit have been done to illustrate the effects of these differences on predicted circuit performance. The differences are significant and arise mainly from differences in the behaviour of coarse particles.     

Toward an environmental justice of the rural-urban interface

In this article, I make the case for an explicit extension of environmental justice research to the rural-urban interface or fringe. A more systematic exploration and synthesis of the blurred boundaries and transitional character of the interface might advance the empirical scope of environmental justice research while contributing to the environmental justice literature’s evolving treatment of space, ecology, and oppression. I subsequently synthesize previous research to outline some fringe characteristics, which signal the interface as a distinct geographical space deserving of closer attention in environmental justice studies, before proposing a few unique dimensions of injustice on the interface. In light of these new facets of rural-urban injustice, I finally outline some preliminary empirical and conceptual questions the interface might pose to environmental justice studies more broadly.