Olga Vizika - Academia.edu (original) (raw)

Papers by Olga Vizika

In this work, we investigated experimentally the relationship between the Capillary Desaturation ... more In this work, we investigated experimentally the relationship between the Capillary Desaturation Curve (CDC) and microscopic properties at the pore scale: the oil cluster size distribution and the porous structure. Experiments were performed on a set of waterwet sandstones with different petrophysical properties. Synchrotron based fast X-ray microtomography was used to capture the dynamics of oil cluster displacements and to get insight into the mechanisms that govern trapped oil mobilization by surfactant injection. Oil cluster size distribution as well as pore geometrical properties were also quantified using lab based microtomography (μ-CT) images at the pore scale. Results showed how the CDC depends on the pore structure and on the oil cluster size distribution at residual oil saturation. We show that rescaling CDC at the macroscopic scale using the relative permeability allows the curves to collapse into one curve. Finally, we propose a new method to predict CDC based on struct...

To speed up coreflood experiments, we have developed a state of the art experimental setup (CAL-X... more To speed up coreflood experiments, we have developed a state of the art experimental setup (CAL-X) designed for high throughput coreflood experimentation. The setup is composed of an X-ray radiography facility, a fully instrumented multi-fluid injection platform and a dedicated X-ray transparent core holder. The equipment was designed to handle small samples of 10 mm in diameter and 20 mm in length, and can be operated at up to 150 bar and 150 °C. The X-ray facility consists of a high-power X-ray tube and a high speed-low noise detector allowing real-time radiography acquisition and offering sufficient density resolution to use dopant-free fluids. The injection platform is fully automated and allows the control and monitoring of different parameters (pressure, temperature, flow rate...). 1-D and 2-D saturation profiles are followed in real-time, allowing a precise determination of the recovery curve, reducing thus drastically timeconsuming effluent measurements. Using this setup, a ...

The influence of stress paths representative of reservoir conditions on the mechanical behavior a... more The influence of stress paths representative of reservoir conditions on the mechanical behavior and the coupled permeability evolutions of a carbonate has been investigated. To predict the permeabilities evolutions under triaxial loading, we have developed a triaxial cell designed to allow the measurements of the permeability in three orthogonal directions, along and transverse to the maximum principal stress direction. A set of core samples are mechanically loaded following different stress paths, characterized by a constant ratio K=∆σH/∆σV. Our experimental set-up allows the monitoring of the petrophysical and geomechanical parameters during loading, before and post sample damage. The tested rock is an analog reservoir carbonate, the Estaillades Limestone, characterized macroscopically by a porosity around φ~29% and a moderate permeability around k~150 mD. From our experimental results, the failure envelope of this carbonate is determined and the evolution of the directional permeabilities are examined in the (p',q) diagram. According to the followed stress path, permeabilities reductions can be limited or drastic. In addition, to identify the micro-mechanisms responsible for the measured permeabilities evolutions, we performed microstructural analyses on deformed samples. In the near-elastic domain, brittle damage induces limited directional permeabilities modifications; whereas, at higher stress, depending on K, shear induced dilation or shear induced compaction mechanisms are activated. The highest permeability drop occurred for the hydrostatic compression (K=1), in the compaction regime, characterized by pore collapse mechanisms affecting preferentially the macroporosity.

All Days, 2009

A Pore Network Model is an efficient tool to account for phenomena occurring at the pore scale. I... more A Pore Network Model is an efficient tool to account for phenomena occurring at the pore scale. Its explicit threedimensional network of pores interconnected by throats enables to easily consider the topology and geometry effects on upscaled and homogenized petrophysical parameters. In particular, this modeling approach is appropriate to study the rock/fluid interactions. It can provide quantitative information both on the effective transport property modifications due to the reactions and on the structure evolution resulting from dissolution/precipitation mechanisms. The developed model is based on the resolution of the macroscopic reactive transport equation between the nodes of the network. By upscaling the results, we have then determined the effective transport properties at the core-scale. A sensitivity study on reactive and flow regimes has been conducted in the case of single-phase flow in the limit of long times. It has been observed that the mean reactive solute velocity a...

Petrophysics, 2003

The dependence of the gas and condensate relative permeabilities and of the critical condensate s... more The dependence of the gas and condensate relative permeabilities and of the critical condensate saturation on the fluid properties (interfacial tensions, densities, and wetting characteristics), the rock structure and the operational parameters (velocity) is still poorly captured by the reservoir simulators. In the present paper a model is proposed based on the dependence of Kr and condensate mobility on two dimensionless numbers: the capillary number (ratio of the viscous to capillary forces) and the Bond number (ratio of the gravity to capillary forces). The spreading characteristics of the condensate on the substrate (solid surface or water film) are also taken into account. The model is tested against experimental results reported in the literature. A very good agreement is obtained indicating that the model captures correctly most of the controlling parameters.

Proceedings of International Petroleum Technology Conference, 2008

Reservoir rocks often present complex pore-structures involving multiple porosity systems with va... more Reservoir rocks often present complex pore-structures involving multiple porosity systems with various interconnectivity patterns. These pore-systems, from microporosity to vugs/fissures, drastically affect petrophysical properties. This is particularly true for electrical properties (formation factor and resistivity index) for which both the amount and spatial distribution of microporosity plays a crucial role.

The objective of the present paper is to look at the effect of small wettability heterogeneities ... more The objective of the present paper is to look at the effect of small wettability heterogeneities (decimetric) on the phase distributions, recovery kinetics and sweep efficiency during a gas injection process. Secondary gas injection experiments have been performed in unconsolidated porous media of well controlled wettability: uniformly water-wet, uniformly oil-wet, and an heterogeneous sandpack consisting of two long water-wet parts separated by a 2 cm thick oil-wet stratum. 3-D saturation profiles of water, oil and gas were obtained with a dual energy CT scanner. The experiments were simulated using a reservoir simulator. In the uniform wettability cases, three-phase relative permeabilities as a function of the three fluids saturations were obtained by history matching of the recovery curves and the experimental saturation profiles. These relative permeabilities along with the corresponding capillary pressures were introduced into a simulator representing the heterogeneous structur...

IOR 2007 - 14th European Symposium on Improved Oil Recovery, 2007

Proceedings of SPE Middle East Oil and Gas Show and Conference, 2005

The injection of carbon dioxide in depleted petroleum reservoirs or in aquifers is a promising wa... more The injection of carbon dioxide in depleted petroleum reservoirs or in aquifers is a promising way to cope with the short-medium term issue of greenhouse gas emissions mitigation. Several coupled physical and chemical processes may occur during the injection depending on time and location within the reservoir. Far field regions are facing long term reaction in a situation where flow of gas and water at a reduced rate may induce near fluid-rock equilibrium. In contrast, near well-bore regions are subjected mainly to gas at a high flow rate where dissolution/reprecipitation phenomena may increase/decrease drastically the injectivity. The purpose of this study is to investigate experimentally the various situations in representative reservoir conditions with the objective of achieving knowledge and data for future physical and numerical modeling and reservoir numerical simulations of CO2 re-injection. Experiments consist in the co-injection of CO2 and brine in carbonate cores (limestone). The temperature and pressure conditions are such that the CO2 is in supercritical state. Results show that the flow rate and the composition of the fluids initially present in the core play a major role in the fluid-rock interaction leading to various non¬uniform dissolution facies and in some cases to re-precipitation and permeability reduction. These phenomena have been observed and quantified using various non destructive techniques (NMR, CT-scanner) and chemical analyses of the producing fluids, leading to a comprehensive understanding of the coupled mechanisms taking place. Introduction This paper is the first step in a laboratory investigation of CO2 sequestration in carbonate reservoirs. It aims at defining qualitatively the consequences of dissolution/precipitation mechanisms on the extent of permeability variations. The coupling of physical and chemical processes occurs in various situations, in the near well bore or far in the reservoir and has consequences on the long term viability of CO2 re-injection in depleted petroleum reservoirs or in aquifers. Whether the injection of CO2 is leading to precipitation or to dissolution, the mechanisms that impact the permeability are still debated. Most of the literature on CO2 injection in the context of oil recovery deals with the WAG process. A survey of the results on field applications showed that the injectivity of CO2 was the first concern of the operators.[1] Based on fluid properties, it is expected a greater CO2 injectivity in comparison to water injectivity. However, in practice, abnormalities[2,3,4] were commonly encountered. Well-bore impairment requiring injection surveillance,[5] particularly in open-hole wells[6] is mentioned. Laboratory experiments were planned in an attempt to identify possible mechanisms responsible of injectivity losses.[7,8] The WAG sequence as well as the presence of residual, i.e. immobile, phases have been pointed out. Two-phase flow and relative permeability effects were investigated without considering chemical mechanisms.[9,10] More recently, with the emerging CO2 sequestration technology, studies dealing with CO2 injection have pointed out the mechanisms of dissolution/precipitation as controlling well injectivities. This study differs from others on several points, which are, in our opinion, basically needed for understanding CO2 flow in the reservoir. First, temperature and pressure are fundamental parameters since they affect the phase diagram. Temperature is also an important factor with regards to reaction kinetics. We chose to work in a situation where the CO2 is in supercritical state. Secondly, we want to account for two important parameters:the flow regime, which varies significantly around the well and can strongly impact the interactions between the circulating fluids and the rock[11] andthe multiphase flow of the CO2 phase and the water, which occurs in the field due to the fractional flow. In this later case, the dissolution products are transported over a certain distance and precipitation may occur in regions non affected by dissolution.[12]

Petrophysics, 2010

The geological storage of CO2 is considered increasingly as a solution to reduce significantly th... more The geological storage of CO2 is considered increasingly as a solution to reduce significantly the emissions in the atmosphere in a near future. Deep aquifers or depleted hydrocarbon reservoirs are considered as the best potential candidates. Previous experimental and numerical work has evidenced that CO2 injection can lead to severe rock/fluid interactions depending on the thermodynamic conditions, the nature of the fluids in place, the rock composition and also the hydrodynamic regime. In the near wellbore region, wormhole dissolution patterns are observed due to the non equilibrium of the geochemical reactions. In the far field region, a homogeneous modification of the pore structure is expected because the dissolution regime is uniform. This paper is related to the phenomena occurring in the far field region. The experimental results demonstrate that the permeability evolution as a function of the dissolution degree is highly dependent on the pore structure and can be as high as 70% increase for roughly 2 porosity units improvement. The second part of the paper is related to the interpretation of the results using the pore network approach. The pore network approach gives a first analysis of the evolution of the rock in terms of porosity and permeability at different dissolution regime. The reaction-limited regime is simulated by uniform dissolution while the reverse case is simulated by pore-body dissolution in diffusion predominant regime and by the pore-throat dissolution in the convection predominant regime. The quantitative comparison with the experimental results indicates the scenario that enables to reproduce satisfactorily the permeability evolution.

Physical Review E, 2011

Standard reservoir evaluations are based on Archie's law relating the average water satur... more Standard reservoir evaluations are based on Archie's law relating the average water saturation to the average electrical resistivity by R(ind) = S(w)(-2). However, especially in the case of complex heterogeneous carbonates, deviation from Archie's law is observed and generally attributed to factors affecting the percolation or disconnectedness of the different phases (wetting films, microporosity, macropores) assuring electrical conductance. Pore-network models (PNM's) in combination with high-resolution computed microtomography (μ-CT) constitute a very effective tool to investigate the influence of the geometry and topology of the porous media on the spatial distribution of the conductive phase, and therefore on the shape of the resistivity index curve. An extended version of the classical PNM applicable to dual-porosity systems is presented. It combines the classical pore-network modeling applied on the macroporous space with the macroscopic properties of the microporous phase, supposing that the two pore systems act in parallel. Three-dimensional images provide information on the connectedness of the microporous phase, which is then included in the simulations. Electrical behavior of sandstone and two carbonates presenting distinct resistivity index curves were simulated and compared to measurements. Both Archie and "non-Archie" behavior were correctly reproduced, and the curve shape was explained considering percolation of the different phases.

Proceedings of SPE Annual Technical Conference and Exhibition, 1999

A mathematical model for three- phase flow has been previously developed and validated in water- ... more A mathematical model for three- phase flow has been previously developed and validated in water- wet and spreading conditions. The model was based on a description of the porous medium considered as a set of fractal pores. The fluids are allowed to flow together in a same pore, gas in the center, and, for water- wet conditions, water in the vicinity of the walls and oil as an intermediate phase. The objective of the present study is to confirm that the above model is able, when properly applied, to describe more general wetting conditions. Three- phase relative permeabilities are obtained by history matching gas injection experiments performed in water- wet and oil- wet porous media. Two fluid systems characterized by spreading and non- spreading of oil on water in presence of gas were used. The model is properly modified to take into account different wetting conditions through a wettability index. It is shown that the model is able to correctly predict oil recovery and breakthroug...

Petrophysics, 2004

Depressurization can be a very interesting process for recovering hydrocarbons from waterflooded ... more Depressurization can be a very interesting process for recovering hydrocarbons from waterflooded oil reservoirs with high gas-oil ratio. Most of the published results are related to depletion experiments under secondary conditions (virgin reservoir). Data are more scarce under tertiary conditions after waterflooding (Ligthelm et al., 1997; Grattoni et al., 1998; Naylor et al., 2000). This paper treats the issue of the depressurization under tertiary conditions in the near-wellbore region. Practically, this has been achieved by combining experimental results, obtained from both core and a transparent micromodel, with radial flow depletion simulations that are representative of the conditions prevailing in the near-wellbore region. A validated methodology previously presented (Egermann and Vizika, 2000) has been used to design the experiments on core (the core under tertiary conditions was continuously flushed with water at a fixed rate, while the pressure at the outlet was decreased ...

Paper description: Modeling of two or three-phase flow in porous media is of prime importance in ... more Paper description: Modeling of two or three-phase flow in porous media is of prime importance in estimating the contamination of soils by liquid organic pollutants and in designing remediation solutions. For an accurate prediction of the transport properties of a porous medium, small-scale data on the pore space geometry and topology are needed. Although the small-scale structure is closely related to the capillary properties of the porous medium, it has been shown (Laroche and Vizika, 2005) that the information derived from a mercury invasion Pc curve is not sufficient to characterize transport properties. The objective of the present work is to evaluate the prediction accuracy of network modeling to calculate transport properties of porous media. The construction of the numerical porous media is based on the interpretation of mercury invasion capillary pressure curve and a relationship between laboratory measurements of formation factor and permeability. A pore-network modeling ap...

E3S Web of Conferences

The phenomenology of steady-state two-phase flow in porous media is recorded in SCAL relative per... more The phenomenology of steady-state two-phase flow in porous media is recorded in SCAL relative permeability diagrams. Conventionally, relative permeabilities are considered to be functions of saturation. Yet, this has been put into challenge by theoretical, numerical and laboratory studies that have revealed a significant dependency on the flow rates. These studies suggest that relative permeability models should include the functional dependence on flow intensities. Just recently a general form of dependence has been inferred, based on extensive simulations with the DeProF model for steady-state two-phase flows in pore networks. The simulations revealed a systematic dependence of the relative permeabilities on the local flow rate intensities that can be described analytically by a universal scaling functional form of the actual independent variables of the process, namely, the capillary number, Ca, and the flow rate ratio, r. In this work, we present the preliminary results of a sys...

SPE Improved Oil Recovery Conference

Petrophysics – The SPWLA Journal of Formation Evaluation and Reservoir Description