Paal-Eric Oeren

• CTO Digital Rock Services at Petricore

The wetting properties of pore walls have a strong effect on multiphase flow through porous media. However, the fluid flow behavior in porous materials with both complex pore structures and non‐uniform wettability are still unclear. Here, we performed unsteady‐state quasi‐static oil‐ and water‐flooding experiments to study multiphase flow in two si...

Image‐based pore‐scale modeling is an important method to study multiphase flow in permeable rocks. However, in many rocks, the pore size distribution is so wide that it cannot be resolved in a single pore‐space image, typically acquired using micro‐computed tomography (micro‐CT). Recent multi‐scale models therefore incorporate sub‐voxel porosity m...

Many properties of complex porous media such as reservoir rocks are strongly affected by heterogeneity at different scales. Complex depositional and diagenetic processes have a strong control on the pore structures, leading to systems with a wide range of pore sizes covering many orders of magnitude in length scales. This poses a significant challe...

We present a pore-network model study of capillary trapping in water-wet porous media. The amount and distribution of trapped non-wetting phase is determined by the competition between two trapping mechanisms - snap-off and cooperative pore-body filling. We develop a new model to describe the pore-body filling mechanism in geologically realistic po...

Digital Rock Analysis (DRA) or pore-scale imaging and modelling have developed significantly in the last decade with the emphasis changing from phenomenological research towards quantitative modelling. The evolution towards more predictive modelling raises questions about the reliability of DRA derived properties compared to experimentally measured...

Heterogeneous rocks with broad pore size distributions, such as carbonates and clay-rich sandstones, often display widely varying behavior. The interaction of micro- and macro-porosity in these complex rocks makes them difficult both to understand and to characterize. Pore scale imaging and modeling has the potential to greatly improve our understa...

This study presents an integrated methodology for determining the pore-scale distribution of wettability of rock samples to guide pore network modeling. Wettability was characterized by spatial registration of rock images from X-ray micro-computed tomography (MCT), Field Emission Scanning Electron Microscopy (FESEM), and Quantitative Evaluation of...

Networks of large pores connected by narrower throats (pore networks) are essential inputs into network models that are routinely used to predict transport properties from digital rock images. Extracting pore networks from microcomputed-tomography (micro-CT) images of rocks involves a number of steps: filtering, segmentation, skeletonization, and o...

Networks of large pores connected by narrower throats (pore networks) are essential inputs into network models which are routinely used to predict transport properties from digital rock images. Extracting pore networks from micro-computed tomography (micro-CT) images of rocks involves a number of steps: filtering, segmentation, skeletonisation etc....

URTeC 1619973 Tight unconventional reservoirs have become an increasingly common target for hydrocarbon production. Exploitation of these resources requires a comprehensive reservoir description and characterization program to estimate reserves, identify properties which control production and account for fracturability. Multiscale imaging studies...

We present a dynamic model of immiscible two-phase flow in a network representation of a porous medium. The model is based on the governing equations describing two-phase flow in porous media, and can handle both drainage, imbibition, and steady-state displacement. Dynamic wetting layers in corners of the pore space are incorporated, with focus on...

We present results from a systematic study of relative permeability functions derived from two-phase lattice Boltzmann (LB) simulations on X-ray microtomography pore space images of Bentheimer and Berea sandstone. The simulations mimic both unsteady- and steady-state experiments for measuring relative permeability. For steady-state flow, we reprodu...

A continuum-based pore-scale representation of a dolomite reservoir rock is presented, containing several orders of magnitude in pore sizes within a single rock model. The macroscale rock fabric from a low-resolution x-ray microtomogram was combined with microscale information gathered from high-resolution two-dimensional electron microscope images...

We present numerical results of electrical resistivity of two-phase flow in reservoir rocks using a dynamic network model. The model accounts for viscous and capillary forces, as well as wetting layers in the crevices of the pore space. It can be used as a unified model for drainage, imbibition and steady-state displacement. We use the model to stu...

Specific internal surface areas and other morphological descriptors of complex disordered systems can be estimated from threedimensional tomographics images using methods of stochastic geometry [1]. Often such data are unavailable for realistic media because these exhibit structural features on multiple length scales. A method to reconstruct stocha...

We present results from simulations of two-phase flow directly on digitized rock microstructure images of porous media using a lattice Boltzmann method. The implemented method is done on a D3Q19 lattice with fluid-fluid and fluid-solid interaction rules to handle interfacial tension and wetting properties. We demonstrate that the model accurately r...

Prediction of petrophysical data by pore network imaging and modelling has recently received a lot of attention. This technique was pioneered by P.E. Øren but several other solutions have now been proposed that incorporate different imaging technologies, different methods for obtaining detailed pore space models, and/or different algorithms for ext...

Using numerical simulations, we study immiscible two-phase flow in a pore network reconstructed from Berea sandstone under flow conditions that are statistically invariant under translation. Under such conditions, the flow is a state function which is not dependent on initial conditions. We find a second-order phase transition resembling the phase...

A stochastic geometrical modeling method for reconstructing three dimensional pore scale microstructures of multiscale porous media is presented. In this method the porous medium is represented by a random but spatially correlated structure of objects placed in the continuum. The model exhibits correlations with the sedimentary textures, scale depe...

In this work we compare four different methods to extract topological skeletons from three dimensional (3D) images of porous media. The applied methods are: (i) medial axis, (ii) maximal ball, (iii) velocity based, and (iv) grain recognition based algorithms. The methods are applied to 3D rock microstructure images of both sandstones and carbonates...

This work investigates two complex, heterogeneous sandstone lithofacies in a North Sea petroleum reservoir field. We compare samples acquired by X-ray microtomography with numerically reconstructed lithofacies, obtained from a geological process based reconstruction technique. Effective material and transport properties of these digitized rocks, su...

A multiscale model for the diagenesis of carbonate rocks is proposed. It captures important pore scale characteristics of carbonate rocks: wide range of length scales in the pore diameters; large variability in the permeability; and strong dependence of the geometrical and transport parameters on the resolution. A pore scale microstructure of an oo...

Laboratory experiments were performed to investigate if water can leak through the pore network of a water wet seal while oil stays in the reservoir below. The experimental setup consisted of a low-permeability membrane disk attached to the outlet side of a cylindrical sandstone core plug. The core plug and the seal were water wet, and the core plu...

We discuss a two-step upscaling workflow to derive field-scale multi-phase flow parameters for depletion. The workflow was designed to increase the quality and reduce the uncertainty related to multi-phase aspects of advanced recovery methods in field-scale reservoir simulation. The upscaling workflow is applied to a realistic model, derived from a...

This paper describes the application of a multi-step, multi-phase upscaling technique to a mature North Sea oil field. The method is aimed at consistently accounting for the effects of small-scale heterogeneities on field simulations. In this work special attention is given to the small-scale (pore-to lithofacies-scale) modeling and upscaling for a...

Depressurisation of waterflooded reservoirs can economically increase recovery and extend the life of mature fields, where mobilization of gas has been found to have a significant impact on both the oil and gas production profiles. This paper describes the determination of critical gas saturation and relative permeabilities relevant to the planned...

TX 75083-3836, U.S.A., fax 01-972-952-9435. Abstract The paper describes an integrated pore-to-field scale modeling method of multiphase flow in porous media. Although the method is general, we demonstrate its power and versatility by modeling a WAG process in the Etive formation in a North Sea oil field. The method aims at capturing the relevant f...

We present an integrated procedure for estimating permeability, conductivity, capillary pressure, and relative permeability of porous media. Although the method is general, we demonstrate its power and versatility on samples of Berea sandstone. The method utilizes petrographical information obtained from 2D thin sections to reconstruct 3D porous me...

TX 75083-3836, U.S.A., fax 01-972-952-9435. Abstract We reconstruct the three-dimensional (3D) microstructure of Fontainebleau sandstone samples of different porosities by a process-based reconstruction method. Permeabilities of the reconstructed media are computed by solving the Stokes equations, while the formation factors are computed by solving...

We present a process based method for reconstructing the full three-dimensional microstructure of sandstones. The method utilizes petrographical information obtained from two-dimensional thin sections to stochastically model the results of the main sandstone forming processes – sedimentation, compaction, and diagenesis. We apply the method to gener...

We reconstruct three-dimensional (3D) Berea sandstone samples by stochastically modeling the results of the main sandstone forming processes. The morphology of the reconstructed microstructure is compared quantitatively with a microtomography image of an actual sample of Berea sandstone. The comparison shows that the process based reconstruction ad...

A quantitative comparison between the experimental microstructure of a sedimentary rock and three theoretical models for the same rock is presented. The microstructure of the rock sample (Fontainebleau sandstone) was obtained by microtomography. Two of the models are stochastic models based on correlation function reconstruction, and one model is b...

A quantitative comparison between the experimental microstructure of a sedimentary rock and three theoretical models for the same rock is presented. The microstructure of the rock sample (Fontainebleau sandstone) was obtained by microtomography. Two of the models are stochastic models based on correlation function reconstruction, and one model is b...

This paper (SPE 52052) was revised for publication from paper SPE 38880, first presented at the 1997 SPE Annual Technical Conference and Exhibition held in San Antonio, Texas, 5-8 October. Original manuscript received for review 21 October 1997. Revised manuscript recieved 22 June 1998. Revised manuscript approved 2 July 1998. Summary We reconstru...

Drainage displacements in three-phase flow under strongly wetting conditions are completely described by a simple generalisation of well understood two-phase drainage mechanisms. As in two-phase flow, the sequence of throat invasions in three-phase flow is determined by fluid connectivity and threshold capillary pressure for the invading interface....

A basic re-examination of the traditional dimensional analysis of microscopic and macroscopic multiphase flow equations in porous media is presented. We introduce a [`(Ca)]\overline {Ca} which differs from the usual microscopic capillary number Ca in that it depends on length scale, type of porous medium and saturation history. The macroscopic capi...

A pore-scale model consisting of a network of pore bodies inter-connected by pore throats is used to calculate drainage relative permeabilities and capillary pressure for a strongly water wet Berea sandstone core. The architecture and geometry of the pore network which is used in the model is constructed from thin section analysis and numerical mod...

This paper presents a precise description of the fluid distribution and pore-scale displacement mechanisms for three-phase flow under strongly wetting conditions when the displacing fluid is a nonwetting phase. It is shown that on the pore-scale the fluids may adopt one of three basic configurations depending on the values of the three interfacial...

This paper describes the basic mechanisms by which waterflood residual oil is mobilized and recovered during tertiary surfactant flooding in strongly water-wet glass micromodels. Of the two models used, one displayed a uniform and the other one a more heterogeneous distribution of water flood residual oil. Mobilization of residual oil proceeds by a...

This paper presents a closed-form analytical solution of the augmented Young-Laplace equation for the meniscus profile in a two-dimensional wedge-shaped capillary. The solution is valid for monotonic forms of disjoining pressure which are repulsive in nature. In the limit of negligible disjoining pressure, it is shown to reduce to the classical sol...

This paper investigates the mobilization and recovery of waterflood residual oil by immiscible gasflooding in 2D glass micromodels under strongly oil- and water-wet conditions. The oil/water/gas systems, one displaying a positive and the other a negative spreading coefficient (oil over water), were used. The results clearly show the importance of f...

This paper investigates the mobilization and recovery of waterflood residual oil by immiscible gasflooding in 2D glass micro-models under strongly oil- and water-wet conditions. Two oil/water/gas systems, one displaying a positive and the other a negative spreading coefficient (oil over water), were used. The results clearly show the importance of...

This paper investigates the wettability behaviour of three rock samples from a Middle Jurassic Brent Group North Sea sandstone reservoir using a combination of traditional Amott and USBM tests, Cryo-SEM and NMR-spectroscopy. From Cryo-SEM observations it is concluded that two of the samples aged in crude oil display an oil-wet to intermediate wet b...

The paper presents a precise description of the pore-scale displacement mechanisms responsible for the mobilization and subsequent recovery of waterflood residual oil by immiscible, gas flooding. The displacement mechanisms are incorporated into a numerical three-phase invasion percolation type network model which is used to compute oil recoveries...

Mechanisms by which waterflood residual oil is mobilized and recovered during tertiary gasflooding at quasistatic rates and strongly water-wet conditions were investigated with 2D glass micromodels. Two three-phase oil/water/gas systems were used in the displacement experiments. One system had a positive spreading coefficient, the other a negative...

The importance of film flow in the displacement of waterflood residual oil by gas flooding in glass micromodels under strongly water wet conditions was studied both experimentally and theoretically. Measured oil and water film thicknesses are presented and compared with film thicknesses computed from a solution of the augmented Young-Laplace equati...

This paper presents the results of an experimental and theoretical study of mechanisms responsible for the evolution and structure of the gas bubble during air-water injection-withdrawal cycles in 2D glass micromodels. Wetting films located in the corners of throat section conduct flow. Wetting film flow generates gas loop structure which increases...

When a gas well is opened at the surface for flow at a constant rate, the initial flow is caused primarily by depletion of gas stored in the wellbore rather than from the formation. The flow from the formation increases gradually from zero until the specified wellhead flowrate is reached. At this point, wellbore storage effects have completely deca...

This paper represents the first contribution in quantifying the effects of wellbore storage along with those of skin and turbulence intensity on deliverability from gas wells. A decay factor, WD, has been introduced to account for the contribution of sandface flow rate to early-time transient production from the gas wells. Generalized charts for ty...

This work investigates the use of an integrated pore-scale modeling procedure to determine reservoir rock parameters from drill cuttings. Our approach is based on reconstructing digital 3D models of reservoir rocks with input data obtained from drill cuttings. A variety of cuttings were investigated, ranging from chips several millimeters in size p...

The prediction of petrophysical and multiphase flow properties from direct pore-scale modeling has received a lot of attention in recent years. Although successful results have been reported for a number of outcrop and reservoir rocks, no exhaustive study has been performed to verify the consistency of such predictions across a wide range of rocks....

In quantitative log interpretation it is common to assume that electrical conductivity is governed by Archie's law. The law is empirical and assumes a clean consolidated sand. Moreover, it also assumes that electrical conductivity is only present in the brine. Archie's law is parameterized by the cementation exponent denoted with m, and the saturat...

We present a general network model to simulate three-phase capillary dominated processes on pore networks extracted from a digitized representation of the rock micro-structure. Important features, such as wettability alteration, hysteresis, intermediate phase spreading layers, and true three-phase capillary entry pressures, are implemented in the m...

We use a geologically based reconstruction technique to generate virtual rocks of complex sandstone lithofacies in a North Sea oil reservoir. Effective properties of the computer generated rocks, such as fluid permeability, electrical resistivity, and elastic moduli, are compared with those determined from microtomographic images of the actual rock...