共查询到20条相似文献,搜索用时 31 毫秒
1.
Jian Li Jishan Liu Michael G. Trefry Keyu Liu Jungho Park Bashirul Haq Colin D. Johnston Michael B. Clennell Herbert Volk 《Transport in Porous Media》2012,92(2):373-396
Residual oil saturation reduction and microbial plugging are two crucial factors in microbial-enhanced oil recovery (MEOR)
processes. In our previous study, the residual saturation was defined as a nonlinear function of the trapping number, and
an explicit relation between the residual oil saturation and the trapping number was incorporated into a fully coupled biological
(B) and hydrological (H) finite element model. In this study, the BH model is extended to consider the impact of rock heterogeneity
on microbial-enhanced oil recovery phenomena. Numerical simulations of core flooding experiments are performed to demonstrate
the influences of different parameters controlling the onset of oil mobilization. X-ray CT core scans are used to construct
numerical porosity-permeability distributions for input to the simulations. Results show clear fine-scale fingering processing,
and that trapping phenomena have significant effects on residual oil saturation and oil recovery in heterogeneous porous media.
Water contents and bacterial distributions for heterogeneous porous media are compared with those for homogenous porous media.
The evolution of the trapping number distribution is directly simulated and visualized. It is shown that the oil recovery
efficiency of EOR/MEOR will be lower in heterogeneous media than in homogeneous media, largely due to the difficulty in supplying
surfactant to unswept low-permeability zones. However, MEOR also provides efficient plugging along high-permeability zones
which acts to increase sweep efficiency in heterogeneous media. Thus, MEOR may potentially be more suited for highly heterogeneous
media than conventional EOR. 相似文献
2.
Microbial enhanced oil recovery (MEOR) is a technology that could potentially increase the tertiary recovery of oil from mature
oil formations. However, the efficacy of this technology in fractional-wet systems is unknown, and the mechanisms involved
in oil mobilization therefore need further investigation. Our MEOR strategy consists of the injection of ex situ produced
metabolic byproducts produced by Bacillus mojavensis JF-2 (which lower interfacial tension (IFT) via biosurfactant production) into fractional-wet cores containing residual oil. Two
different MEOR flooding solutions were tested; one solution contained both microbes and metabolic byproducts while the other
contained only the metabolic byproducts. The columns were imaged with X-ray computed microtomography (CMT) after water flooding,
and after MEOR, which allowed for the evaluation of the pore-scale processes taking place during MEOR. Results indicate that
the larger residual oil blobs and residual oil held under relatively low capillary pressures were the main fractions recovered
during MEOR. Residual oil saturation, interfacial curvatures, and oil blob sizes were measured from the CMT images and used
to develop a conceptual model for MEOR in fractional-wet systems. Overall, results indicate that MEOR was effective at recovering
oil from fractional-wet systems with reported additional oil recovered (AOR) values between 44 and 80%; the highest AOR values
were observed in the most oil-wet system. 相似文献
3.
Sidsel M. Nielsen Alexander A. Shapiro Michael L. Michelsen Erling H. Stenby 《Transport in Porous Media》2010,85(3):785-802
We have developed a mathematical model describing the process of microbial enhanced oil recovery (MEOR). The one-dimensional
isothermal model comprises displacement of oil by water containing bacteria and substrate for their feeding. The bacterial
products are both bacteria and metabolites. In the context of MEOR modeling, a novel approach is partitioning of metabolites
between the oil and the water phases. The partitioning is determined by a distribution coefficient. The transfer part of the
metabolite to oil phase is equivalent to its ”disappearance,” so that the total effect from of metabolite in the water phase
is reduced. The metabolite produced is surfactant reducing oil–water interfacial tension, which results in oil mobilization.
The reduction of interfacial tension is implemented through relative permeability curve modifications primarily by lowering
residual oil saturation. The characteristics for the water phase saturation profiles and the oil recovery curves are elucidated.
However, the effect from the surfactant is not necessarily restricted to influence only interfacial tension, but it can also
be an approach for changing, e.g., wettability. The distribution coefficient determines the time lag, until residual oil mobilization
is initialized. It has also been found that the final recovery depends on the distance from the inlet before the surfactant
effect takes place. The surfactant effect position is sensitive to changes in maximum growth rate, and injection concentrations
of bacteria and substrate, thus determining the final recovery. Different methods for incorporating surfactant-induced reduction
of interfacial tension into models are investigated. We have suggested one method, where several parameters can be estimated
in order to obtain a better fit with experimental data. For all the methods, the incremental recovery is very similar, only
coming from small differences in water phase saturation profiles. Overall, a significant incremental oil recovery can be achieved,
when the sensitive parameters in the context of MEOR are carefully dealt with. 相似文献
4.
The focus of this paper is the derivation of a nonstandard model for microbial enhanced oil recovery (MEOR) that includes the interfacial area (IFA) between oil and water. We consider the continuity equations for water and oil, a balance equation for the oil–water interfacial area, and advective–dispersive transport equations for bacteria, nutrients, and biosurfactants. Surfactants lower the interfacial tension (IFT), which improves oil recovery. Therefore, the parametrizations of the IFT reduction and residual oil saturation are included as a function of the surfactant concentration in the model. We consider for the first time in context of MEOR, the role of IFA in enhanced oil recovery. The motivation to include the IFA is to model the hysteresis in the capillary pressure–saturation relationship in a physically based manner, to include the effects of observed bacteria migration toward the oil–water interface and the production of biosurfactants at the oil–water interface. A comprehensive 2D implementation based on two-point flux approximation and backward Euler is proposed. An efficient and robust linearization scheme is used to solve the nonlinear systems at each time step. Illustrative numerical simulations are presented. The differences in the oil recovery profiles obtained with and without IFA are discussed. The presented model can also be used to design new experiments toward a better understanding and eventually optimization of MEOR. 相似文献
5.
We present a dynamic pore-scale network model of imbibition, capable of calculating residual oil saturation for any given capillary number, viscosity ratio, contact angle, and aspect ratio. Our goal is not to predict the outcome of core floods, but rather to perform a sensitivity analysis of the above-mentioned parameters, except from the viscosity ratio. We find that contact angle, aspect ratio, and capillary number all have a significant influence on the competition between piston-like advance, leading to high recovery, and snap-off, causing oil entrapment. Due to significant CPU-time requirements we did not incorporate long-range correlations among pore and throat sizes in our network, but were limited to small-range correlations. Consequently, the gradual suppression of snap-off occurs within one order of magnitude of the capillary number. At capillary numbers around 108 - 107 snap-off has been entirely inhibited, in agreement with results obtained by Blunt (1997) who used a quasi-static model. For higher aspect ratios, the effect of rate and contact angle is more pronounced. 相似文献
6.
Multiphase flow with a simplified model for oil entrapment 总被引:3,自引:0,他引:3
A computationally simple procedure is described to model effects of oil entrapment on three-phase permeability-saturation-capillary pressure relations. The model requires knowledge of airwater saturation-capillary pressure relations, which are assumed to be nonhysteretic and are characterized by Van Genuchten's parametric model; scaling factors equal to the ratio of water surface tension to oil surface tension and to oil-water interfacial tension; and the maximum oil (also referred to as nonwetting liquid in a three-phase medium) saturation which would occur following water flooding of oil saturated soil. Trapped nonwetting liquid saturation is predicted as a function of present oil-water and air-oil capillary pressures and minimum historical water saturation since the occurrence of oil at a given location using an empirically-based algorithm. Oil relative permeability is predicted as a simple function of apparent water saturation (sum of actual water saturation and trapped oil saturation) and free oil saturation (difference between total oil and trapped oil saturation), and water relative permeability is treated as a unique function of actual water saturation. The proposed method was implemented in a two-dimensional finite-element simulator for three-phase flow and component transport, MOFAT. The fluid entrapment model requires minimal additional computational effort and computer storage and is numerically robust. The applicability of the model is illustrated by a number of hypothetical one- and two-dimensional simulations involving infiltration and redistribution with changes in water-table elevations. Results of the simulations indicate that the fraction of a hydrocarbon spill that becomes trapped under given boundary conditions increases as a nonlinear function of the maximum trapped nonwetting liquid saturation. Dense organic liquid plumes may exhibit more pronounced effects of entrapment due to the more dynamic nature of flow, even under static water table conditions. Disregarding nonwetting fluid entrapment may lead to significant errors in predictions of immiscible plume migration. 相似文献
7.
A novel concept for modeling pore-scale phenomena included in several enhanced oil recovery (EOR) methods is presented. The
approach combines a quasi-static invasion percolation model with a single-phase dynamic transport model in order to integrate
mechanistic chemical oil mobilization methods. A framework is proposed that incorporates mobilization of capillary trapped
oil. We show how double displacement of reservoir fluids can contribute to mobilize oil that are capillary trapped after waterflooding.
In particular, we elaborate how the physics of colloidal dispersion gels (CDG) or linked polymer solutions (LPS) is implemented.
The linked polymer solutions consist of low concentration partially hydrolyzed polyacrylamide polymer crosslinked with aluminum
citrate. Laboratory core floods have shown demonstrated increased oil recovery by injection of linked polymer solution systems.
LPS consist of roughly spherical particles with sizes in the nanometer range (50–150 nm). The LPS process involve mechanisms
such as change in rheological properties effect, adsorption and entrapment processes that can lead to a microscopic diversion
and mobilization of waterflood trapped oil. The purpose is to model the physical processes occurring on pore scale during
injection of linked polymer solutions. A sensitivity study has also been performed on trapped oil saturation with respect
to wettability status to analyze the efficiency of LPS on different wettability conditions. The network modeling results suggest
that weakly wet reservoirs are more suitable candidates for performing linked polymer solution injection. 相似文献
8.
Sensitivity Analysis of the Dimensionless Parameters in Scaling a Polymer Flooding Reservoir 总被引:1,自引:0,他引:1
A set of scaling criteria of a polymer flooding reservoir is derived from the governing equations, which involve gravity and
capillary force, compressibility of water, oil, and rock, non-Newtonian behavior of the polymer solution, absorption, dispersion,
and diffusion, etc. A numerical approach to quantify the dominance degree of each dimensionless parameter is proposed.With
this approach, the sensitivity factor of each dimensionless parameter is
evaluated. The results show that in polymer flooding, the order of the sensitivity factor ranges from 10−5 to 100 and the dominant dimensionless parameters are generally the ratio of the oil permeability under the condition of the irreducible
water saturation to water permeability under the condition of residual oil saturation, density, and viscosity ratios between
water and oil, the reduced initial oleic phase saturation and the shear rate exponent of the polymer solution. It is also
revealed that the dominant dimensionless parameters may be different from case to case. The effect of some physical variables,
such as oil viscosity, injection rate, and permeability, on the dominance degree of the dimensionless parameters is analyzed
and the dominant ones are determined for different cases. 相似文献
9.
In oil recovery from fractured reservoirs, dynamic spontaneous imbibition (DSI) plays an important role. Conventional equations
used for characterizing dynamic spontaneous imbibition neglect the effects of the driving forces acting across the wetting
and non-wetting phases which are flowing in opposite directions. Such effects, defined as interfacial coupling effects (ICE),
are known to cause a decrease in the calculated flow rate in drainage processes. Moreover, none of the numerical models have
considered a variable inlet saturation (S*) for DSI. A new theoretical model has been developed using generalized transport equations to describe dynamic spontaneous
imbibition for immiscible two-phase flow processes. The inclusion of interfacial coupling effects provides a more accurate
way to describe dynamic spontaneous imbibition. Furthermore, the addition of variable inlet saturation allows one to establish
whether the inlet-face saturation (S*) increases from the initial saturation to 1−Sro, or whether it can remain constant and equal to one minus the residual saturation
to the non-wetting phase (1−Sro). 相似文献
10.
A parametric two-phase, oil–water relative permeability/capillary pressure model for petroleum engineering and environmental applications is developed for porous media in which the smaller pores are strongly water-wet and the larger pores tend to be intermediate- or oil-wet. A saturation index, which can vary from 0 to 1, is used to distinguish those pores that are strongly water-wet from those that have intermediate- or oil-wet characteristics. The capillary pressure submodel is capable of describing main-drainage and hysteretic saturation-path saturations for positive and negative oil–water capillary pressures. At high oil–water capillary pressures, an asymptote is approached as the water saturation approaches the residual water saturation. At low oil–water capillary pressures (i.e. negative), another asymptote is approached as the oil saturation approaches the residual oil saturation. Hysteresis in capillary pressure relations, including water entrapment, is modeled. Relative permeabilities are predicted using parameters that describe main-drainage capillary pressure relations and accounting for how water and oil are distributed throughout the pore spaces of a porous medium with mixed wettability. The capillary pressure submodel is tested against published experimental data, and an example of how to use the relative permeability/capillary pressure model for a hypothetical saturation-path scenario involving several imbibition and drainage paths is given. Features of the model are also explained. Results suggest that the proposed model is capable of predicting relative permeability/capillary pressure characteristics of porous media mixed wettability. 相似文献
11.
We investigated the mechanism of residual gas trapping at a microscopic level. We imaged trapped air bubbles in a Berea sandstone
chip after spontaneous imbibition at atmospheric pressure. The pore structure and trapped bubbles were observed by microfocused
X-ray computed tomography. Distributions of trapped bubbles in Berea and Tako sandstone were imaged in coreflooding at a capillary
number of 1.0 × 10−6. Trapped bubbles are of two types, those occupying the center of the pore with a pore-scale size and others having a pore-network
scale size. In low-porosity media such as sandstone, connected bubbles contribute greatly to trapped gas saturation. Effects
of capillary number and injected water volume were investigated using a packed bed of glass beads 600μm in diameter, which
had high porosity (38%). The trapped N2 bubbles are stable against the water flow rate corresponding to a capillary number of 1.0 × 10−4. 相似文献
12.
Modeling of the processes of elution from porous systems is essential importance for development of the removing oily contaminations from the soils and intensification of the oil recovery processes. In the paper, capillary model of gravitational elution of high viscosity substances from the porous medium by using low viscosity liquids was derived. This model allowed for the prediction of changes in time of such parameters like: level of bed saturation with oil, relative bed permeability, liquid flow rate, flow resistance, volume of eluted liquid during the process. When modeling, phenomena and the physical properties associated with the analyzed process, such as, for example, the effects of surface tension, fluids viscosity, specific size of the granular bed, initial oil saturation of bed, variable process driving force, and the flow of liquid through the preferential flow paths, were taken into account. This allowed for the more complete imaging of elution process. The model has been verified on the basis of the results of experimental studies. In addition, the discussion on the behavior of the model due to changes in values of various parameters was carried out. 相似文献
13.
14.
A model has been derived theoretically to correlate capillary pressure and resistivity index based on the fractal scaling
theory. The model is simple and predicts a power law relationship between capillary pressure and resistivity index (P
c
= p
e
· I
β) in a specific range of low water saturation. To verify the model, gas-water capillary pressure and resistivity were measured
simultaneously at a room temperature in 14 core samples from two formations in an oil reservoir. The permeability of the core
samples ranged from 0.028 to over 3000 md. The porosity ranged from less than 8 to over 30. Capillary pressure curves were
measured using a semi-permeable porous-plate technique. The model was tested against the experimental data obtained in this
study. The results demonstrated that the model could match the experimental data in a specific range of low water saturation.
The experimental results also support the fractal scaling theory in a low water saturation range. The new model developed
in this study may be deployed to determine capillary pressure from resistivity data both in laboratories and reservoirs, especially
in the case in which permeability is low or it is difficult to measure capillary pressure. 相似文献
15.
New Trapping Mechanism in Carbon Sequestration 总被引:1,自引:0,他引:1
The modes of geologic storage of CO2 are usually categorized as structural, dissolution, residual, and mineral trapping. Here we argue that the heterogeneity
intrinsic to sedimentary rocks gives rise to a fifth category of storage, which we call local capillary trapping. Local capillary
trapping occurs during buoyancy-driven migration of bulk phase CO2 within a saline aquifer. When the rising CO2 plume encounters a region (10−2 to 10+1m) where capillary entry pressure is locally larger than average, CO2 accumulates beneath the region. This form of storage differs from structural trapping in that much of the accumulated saturation
will not escape, should the integrity of the seal overlying the aquifer be compromised. Local capillary trapping differs from
residual trapping in that the accumulated saturation can be much larger than the residual saturation for the rock. We examine
local capillary trapping in a series of numerical simulations. The essential feature is that the drainage curves (capillary
pressure versus saturation for CO2 displacing brine) are required to be consistent with permeabilities in a heterogeneous domain. In this work, we accomplish
this with the Leverett J-function, so that each grid block has its own drainage curve, scaled from a reference curve to the permeability and porosity
in that block. We find that capillary heterogeneity controls the path taken by rising CO2. The displacement front is much more ramified than in a homogeneous domain, or in a heterogeneous domain with a single drainage
curve. Consequently, residual trapping is overestimated in simulations that ignore capillary heterogeneity. In the cases studied
here, the reduction in residual trapping is compensated by local capillary trapping, which yields larger saturations held
in a smaller volume of pore space. Moreover, the amount of CO2 phase remaining mobile after a leak develops in the caprock is smaller. Therefore, the extent of immobilization in a heterogeneous
formation exceeds that reported in previous studies of buoyancy-driven plume movement. 相似文献
16.
Recovery of oil from the blocks of an initially oil-wet, naturally fractured, reservoir as a result of counter-current flow
following introduction of aqueous wettability-altering surfactant into the fracture system is considered, as an example of
a practical process in which phenomena acting at the single pore-scale are vital to the economic displacement of oil at the
macroscopic scale. A Darcy model for the process is set up, and solutions computed illustrating the recovery rate controlling
role of the bulk diffusion of surfactant. A central ingredient of this model is the capillary pressure relation, linking the
local values of the pressure difference between the oleic and aqueous phases, the aqueous saturation and the surfactant concentration.
Using ideas from single capillary models of oil displacement from oil-wet tubes by wettability-altering surfactant, we speculate
that the use of a capillary pressure function, with dependences as assumed, may not adequately represent the Darcy scale consequences
of processes acting at the single pore-scale. Multi-scale simulation, resolving both sub-pore and multi-pore flow processes
may be necessary to resolve this point. Some general comments are made concerning the issues faced when modelling complex
displacement processes in porous media starting from the pore-scale and working upwards. 相似文献
17.
Models of the residual oil saturation distribution are proposed for linear, axisymmetric, and general flows. The steady displacing
fluid flow model makes it possible to find equilibrium residual oil saturation distributions corresponding to given flow regimes
by treating the porous medium with capillary-trapped oil as a medium with permeability that depends on the displacement conditions.
The dynamics of the mobilized globules of the residual oil are excluded from consideration. The simulation results indicate
that the residual oil saturation distribution after stimulation of the wash-out zone by means of enhanced oil recovery techniques
is generally essentially nonuniform.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 3, pp. 98–104, May–June, 2000. 相似文献
18.
Chinedu C. Agbalaka Abhijit Y. Dandekar Shirish L. Patil Santanu Khataniar James R. Hemsath 《Transport in Porous Media》2009,76(1):77-94
In this work, coreflood studies were carried out to determine the recovery benefits of low salinity waterflood compared to
high salinity waterflood and the role of wettability in any observed recovery benefit. Two sets of coreflood experiments were
conducted; the first set examined the EOR potential of low salinity floods in tertiary oil recovery processes, while the second
set of experiments examined the secondary oil recovery potential of low salinity floods. Changes in residual oil saturation
with variation in wettability, brine salinity and temperature were monitored. All the coreflood tests gave consistent increase
in produced oil, corresponding to reduction in residual oil saturation and increase in water-wetness (for the second set of
experiments) with decrease in brine salinity and increase in brine temperature. 相似文献
19.
Krista M. Kaster Aksel Hiorth Grethe Kjeilen-Eilertsen Kate Boccadoro Arild Lohne Harald Berland Arne Stavland Odd Gunnar Brakstad 《Transport in Porous Media》2012,91(1):59-79
Microbial enhanced oil recovery (MEOR) represents a possible cost-effective tertiary oil recovery method. Although the idea
of MEOR has been around for more than 75 years, even now little is known of the mechanisms involved. In this study, Draugen
and Ekofisk enrichment cultures, along with Pseudomonas spp. were utilized to study the selected MEOR mechanisms. Substrates which could potentially stimulate the microorganisms
were examined, and l-fructose, d-galacturonic acid, turnose, pyruvic acid and pyruvic acid methyl ester were found to be the best utilized by the Ekofisk
fermentative enrichment culture. Modelling results indicated that a mechanism likely to be important for enhanced oil recovery
is biofilm formation, as it required a lower in situ cell concentration compared with some of the other MEOR mechanisms. The
bacterial cells themselves were found to play an important role in the formation of emulsions. Bulk coreflood and flow cell
experiments were performed to examine MEOR mechanisms, and microbial growth was found to lead to possible alterations in wettability.
This was observed as a change in wettability from oil wet (contact angle 154°) to water wet (0°) due to the formation of biofilms
on the polycarbonate coupons. 相似文献
20.
Adrian P. Sheppard Ji-Youn Arns Mark A. Knackstedt W. Val Pinczewski 《Transport in Porous Media》2005,59(2):155-173
Quasi-static rule-based network models used to calculate capillary dominated multi-phase transport properties in porous media employ equilibrium fluid saturation distributions which assume that pores are fully filled with a single bulk fluid with other fluids present only as wetting and/or spreading films. We show that for drainage dominated three-phase displacements in which a non-wetting fluid (gas) displaces a trapped intermediate fluid (residual oil) in the presence of a mobile wetting fluid (water) this assumption distorts the dynamics of three-phase displacements and results in significant volume errors for the intermediate fluid and erroneous calculations of intermediate fluid residual saturations, relative permeabilities and recoveries. The volume errors are associated with the double drainage mechanism which is responsible for the mobilization of waterflood residual oil. A simple modification of the double drainage mechanism is proposed which allows the presence of a relatively small number of partially filled pores and removes the oil volume errors. 相似文献