scholarly journals Unsteady-state behavior of coastal groundwater: a sand tank experiment.

2001 ◽  
Vol 62 (1) ◽  
pp. 41-50
Author(s):  
Kunimitsu INOUCHI ◽  
Tadao KAKINUMA
Keyword(s):  
Unsteady State ◽  
State Behavior ◽  
Coastal Groundwater ◽  
Tank Experiment

Unsteady-State Behavior of Naturally Fractured Reservoirs

1965 ◽  
Vol 5 (01) ◽  
pp. 60-66 ◽  
Author(s):  
A.S. Odeh
Keyword(s):  
Fractured Reservoirs ◽  
Naturally Fractured Reservoirs ◽  
Unsteady State ◽  
Fractured Reservoir ◽  
State Behavior ◽  
Naturally Fractured ◽  
Matrix Blocks ◽  
The Matrix ◽  
Porosity And Permeability ◽  
Bulk Volume

Abstract A simplified model was employed to develop mathematically equations that describe the unsteady-state behavior of naturally fractured reservoirs. The analysis resulted in an equation of flow of radial symmetry whose solution, for the infinite case, is identical in form and function to that describing the unsteady-state behavior of homogeneous reservoirs. Accepting the assumed model, for all practical purposes one cannot distinguish between fractured and homogeneous reservoirs from pressure build-up and/or drawdown plots. Introduction The bulk of reservoir engineering research and techniques has been directed toward homogeneous reservoirs, whose physical characteristics, such as porosity and permeability, are considered, on the average, to be constant. However, many prolific reservoirs, especially in the Middle East, are naturally fractured. These reservoirs consist of two distinct elements, namely fractures and matrix, each of which contains its characteristic porosity and permeability. Because of this, the extension of conventional methods of reservoir engineering analysis to fractured reservoirs without mathematical justification could lead to results of uncertain value. The early reported work on artificially and naturally fractured reservoirs consists mainly of papers by Pollard, Freeman and Natanson, and Samara. The most familiar method is that of Pollard. A more recent paper by Warren and Root showed how the Pollard method could lead to erroneous results. Warren and Root analyzed a plausible two-dimensional model of fractured reservoirs. They concluded that a Horner-type pressure build-up plot of a well producing from a factured reservoir may be characterized by two parallel linear segments. These segments form the early and the late portions of the build-up plot and are connected by a transitional curve. In our analysis of pressure build-up and drawdown data obtained on several wells from various fractured reservoirs, two parallel straight lines were not observed. In fact, the build-up and drawdown plots were similar in shape to those obtained on homogeneous reservoirs. Fractured reservoirs, due to their complexity, could be represented by various mathematical models, none of which may be completely descriptive and satisfactory for all systems. This is so because the fractures and matrix blocks can be diverse in pattern, size, and geometry not only between one reservoir and another but also within a single reservoir. Therefore, one mathematical model may lead to a satisfactory solution in one case and fail in another. To understand the behavior of the pressure build-up and drawdown data that were studied, and to explain the shape of the resulting plots, a fractured reservoir model was employed and analyzed mathematically. The model is based on the following assumptions:1. The matrix blocks act like sources which feed the fractures with fluid;2. The net fluid movement toward the wellbore obtains only in the fractures; and3. The fractures' flow capacity and the degree of fracturing of the reservoir are uniform. By the degree of fracturing is meant the fractures' bulk volume per unit reservoir bulk volume. Assumption 3 does not stipulate that either the fractures or the matrix blocks should possess certain size, uniformity, geometric pattern, spacing, or direction. Moreover, this assumption of uniform flow capacity and degree of fracturing should be taken in the same general sense as one accepts uniform permeability and porosity assumptions in a homogeneous reservoir when deriving the unsteady-state fluid flow equation. Thus, the assumption may not be unreasonable, especially if one considers the evidence obtained from examining samples of fractured outcrops and reservoirs. Such samples show that the matrix usually consists of numerous blocks, all of which are small compared to the reservoir dimensions and well spacings. Therefore, the model could be described to represent a "homogeneously" fractured reservoir. SPEJ P. 60ˆ

scholarly journals Study of Unsteady State Behavior of Foam in Surfactant-Alternating-Gas Process

2016 ◽  
Vol 9 (28) ◽  
Author(s):  
Hamed Hematpour ◽  
Syed Mohammad Mahmood ◽  
Mohammad Khan Memon ◽  
Ali Mohammad Mongy
Keyword(s):  
Unsteady State ◽  
State Behavior

scholarly journals Decision making in goverment tenders: A formalized qualitative model

2012 ◽  
Vol 60 (4) ◽  
pp. 397-406 ◽  
Author(s):  
Štěpán Veselý ◽  
Mirko Dohnal
Keyword(s):  
A Priori ◽  
Oriented Graph ◽  
Relevant Information ◽  
Qualitative Model ◽  
Unsteady State ◽  
Qualitative Modeling ◽  
State Behavior ◽  
Qualitative Models ◽  
Goal Functions ◽  
Available Information

The paper presents a simple formalized qualitative model of government tenders (GTs). Qualitative models use just three values: Positive/Increasing, Zero/Constant and Negative/Decreasing. Such quantifiers of trends are the least information intensive. Qualitative models can be useful, since GT evaluation often includes such goals as e.g. efficiency of public purchasing, and variables as e.g. availability of relevant information or subjectivity of judgment, that are difficult to quantify. Hence, a significant fraction of available information about GTs is not of numerical nature, e.g.if availability of relevant information is decreasing then efficiency of public purchasing is decreasing as well. Such equationless relations are studied in this paper. A qualitative model of the function F(Goals, Variables) is developed. The model has four goal functions, eight variables, and 39 equationless relations. The model is solved and seven solutions, i.e. scenarios are obtained. All qualitative states, including first and second qualitative derivatives with respect to time, of all variables are specified for each scenario. Any unsteady state behavior of the GT model is described by its transitional oriented graph. There are eight possible transitions among seven scenarios. No a priori knowledge of qualitative modeling is required on the reader’s part.

Unsteady state behavior of CO oxidation over a supported Pt catalyst in the millibar range

1998 ◽  
Vol 65 (1) ◽  
pp. 3-8 ◽  
Author(s):  
G. Bonilla ◽  
T. D. Pletcher ◽  
G. Haas ◽  
J. Lauterbach
Keyword(s):  
Co Oxidation ◽  
Pt Catalyst ◽  
Unsteady State ◽  
State Behavior ◽  
Supported Pt Catalyst
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