The mechanical and transport properties of porous and cracked media, such as velocity and permeability, are sensitive to the effects of effective pressure, which itself is a function of the confining pressure and the pore-fluid pressure. The dependence of permeability and velocity on effective pressure has previously been modeled using the Bed-of-Nails asperity-deformation model. The main objective of this research was to explore the sensitivity of the Bed-of-Nails and effective-pressure models to random, Gaussian errors, by using an inverse approach. To achieve this, numerical modeling of pre-existing velocity and permeability experimental data sets was done. Extrapolation to 600 MPa was performed using an epidosite data set of compressional velocity as a function of confining pressure, only using measurements in the range 0-100 MPa. The results showed that, given sufficient data and considering random error only, extrapolation can be done with a level of error of less than 1.5%. Model error can also be significant in this type of exercise because it can give rise to systematic misfit, although in this case it was shown that the effects of model error were not considerable. Modeling the variation of compressional velocities as a function of confining and pore-fluid pressures in a deep-sea chalk showed that the best-fitting asperity-deformation model is sensitive to the effective-pressure model. Measurements of permeability in a Navajo-sandstone specimen as a function of confining pressure were numerically modeled, and the results showed that measurements made at low pressures, specifically near Pe = 0, are very important to constrain the model. The same result was found in the case of permeability as a function of confining and pore-fluid pressure in a Wilcox-shale where the lack of measurements near Pe = 0 caused the error in the model parameters to be overestimated. This occurs because the rate of change of permeability as a function of effective pressure is very high at low pressures. The lack of sufficient data near Pe = 0 overestimates the curvature matrix and, therefore, the errors in the model parameters.

In this paper, the slipping friction is considered in the problem of a progressive wave of real fluids propagating over a permeable bottom. In the interface of soil and fluid, the ¡§no-slip¡¨ condition is relaxed and a sliding friction coefficient is introduced. Thus, the slipping effect and the permeability of bottom on the velocity near the seabed can be studied. The results indicate that the joint effect of slipping friction and permeability is crucial. The overshooting phenomena also can be explained by this joint effect.

Tight gas reservoirs are those reservoirs where the matrix has a low permeability range (k < 0.1 md). The literature documents laboratory experiments under restressed conditions that show stress dependent rock properties are more significant in tighter rocks. For gas reservoirs, real gas properties are also sensitive to variations of pressure, and the correct description of gas flow must include pressure-dependent gas properties. Under these circumstances the resulting equation for real gas flow is a second order, non-linear, partial differential equation. Non-linearities include pressure-dependence of gas viscosity, gas compressibility, reservoir permeability and reservoir porosity. This paper investigates dynamic permeability change as a function of net overburden stress in tight gas reservoirs. The gas reservoir simulator used for this work included pressure-dependent reservoir permeability. Radial flow cases are analyzed using this simulator. During this study we found that from analysis of production data alone, it is impossible to determine the correct permeability value for tight gas reservoirs with pressure-dependent permeability. For the cases studied, the transient performance was similar for both constant permeability and pressure-dependent permeability. This similarity causes constant permeability and pressure-dependent permeability to be indistinguishable, based on analysis of transient performance data. It was found that the productivity index decreases when pressure-dependent permeability is more significant. Finally, this study verified that the method of Ibrahim et al.28 under estimates original gas in place (OGIP) for tight gas reservoirs with pressure-dependent permeability.

Interference for adjacent wells may be beneficial to Coalbed-Methane production. The effect is the acceleration of de-watering which should lead to earlier and higher gas rate peaks. It is inherent that permeability anisotropy exists in the coalbed methane formation. It means that the placement of wells (wells configuration) has an effect on the development of coalbed methane field. The effect of Palmer-Mansoori Theory is increasing effective permeability at lower pressures due to matrix shrinkage during desorption. This effect should increase the gas recovery of coalbed methane production. Palmer and Mansoori model should be considered and included to coalbed methane reservoir simulation. These effects and phenomena can be modeled with the CMG simulator. A systematic sensitivity study of various reservoir and operating parameters will result in generalized guidelines for operating these reservoirs more effectively.

Thesis (doctoral)--Universität Kiel, 2000. / Vita. Includes bibliographical references (p. 138-145).

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Understanding pore network structure of a porous medium and fluid flow in the pore network has been an interest to researchers for decades. This study focuses on the characterization and simulation of the pore networks in petroleum reservoir rocks using conventional characterization techniques. A Representative Elemental Volume (REV) model is developed which simulates the pore network as a series of non-interconnected capillary tubes of varying sizes. The model implements mercury porosimetry (MP) results and capillary pressure principles to calculate the size of each bundle of capillary tubes based on a pore throat size distribution produced by the MP experiment. It also implements electrical properties of the rocks to estimate the average length of the capillary tubes. To verify the validity of the simulated network, permeability is calculated for the simulated network using Poiseuille’s flow principles for capillary tubes. Preliminary work showed that the model is capable of simulating the pore network reasonably well because permeability estimations for the simulated network matched measurements. In this study, MP and nuclear magnetic resonance (NMR) tests as well as centrifuge and permeability tests are performed on a suite of 11 sandstone and carbonate rock samples. Because electrical tests were not available, average length of flow paths is calculated with an alternative method that uses porosity to calculate tortuosity. Permeability estimations of the simulated network are compared with measurements. Estimations are also compared to other predictions using methods that implement MP and NMR data to simulate the pore network and the results show that the developed REV model out performs all the other techniques. / October 2015