Applying Fractional-Flow Theory Under the Loss of Miscibility (original) (raw)
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SPE Reservoir Engineering, 1993
Summary This paper presents an experimental study that uses many slim-tube displacements to characterize the effect of hydrocarbon solvent composition on miscibility development. It was found that the minimum enrichment requirement can be estimated reliably with a previously proposed pseudocritical temperature, Tpc, concept. Tuning equation-of-state (EOS) parameters to match these results required incorporating rate and recoveries from selected slim-tube displacement tests in addition to conventional PVT data.
International Journal of Geomate, 2017
ABSTRACT: This paper evaluates and compares the effect of fractional flow and relative permeability of heavy oil and Kerosene during recovery in a petroleum reservoir. Water fingering is one of the challenging problems during oil recovery and another comprehensive problem is, to exactly evaluate the amount of recover oil from a petroleum reservoir. To address these problems, the fractional flow and relative permeability of heavy oil and Kerosene are analyzed. The fractional flow approach is originated in the petroleum engineering literature and employs the saturation of one of the phases and a pressure as the independent variables. The fractional flow approach treats the multi-phases flow problem as a total fluid of a single mixed fluid and then describes the individual phases as fractional of the total flow. Laboratory steady state flow experiments are performed in two different types of oils (Heavy oil and Kerosene), to empirically obtain relative permeability and fractional flow ...
Journal of Petroleum Science and Engineering, 2018
The objective of Low Salinity Water Flooding (LSWF) is to improve oil recovery. While a significant number of laboratory tests have been carried out to investigate the impact of LSWF, field scale modelling is often reported in the form of sector models with relatively coarse cells. This paper assesses the impact of simulating flow at very fine scales and informs on the properties that should be captured at the coarse scale to avoid numerical errors. We have found that the weighting function that is used to control changes to fluid mobility combines with numerical and physical diffusion to induce a retardation/acceleration effect. This is a physical effect rather than part of a chemical reaction. In this study, numerous simulations of LSWF have been carried out at the reservoir scale to investigate flow behavior for various salt concentration (salinity) weighting functions and dispersion coefficients. We have examined the effective salinity range over which the weighting function is applied as well as considering various shapes. Dispersion was varied to represent physical and numerical effects. These have been compared to analytical solutions from fractional flow theory. We also observed that the fractional flow of the oil bank will be same for both the secondary and tertiary flooding. We point out the relative importance of various parts of the relative permeability curves. An important finding of this work is that by spreading the salinity front through dispersion and setting a low value at which salinity impacts mobility, we saw the injected low salinity front advance more slowly while the high salinity front of formation water moves more quickly. This is an effective retardation effect. We related this to an effect equivalent to adsorption in the fractional flow theory and could measure it in a similar way. We were also able to develop a prediction of the effect using the analytical solution to the advection-diffusion equation. The outcome is that we can estimate a corrective term for the flow behavior in situations where the dispersion is quite strong, particularly in numerical simulations. We consider that this enable corrections to be made for numerical dispersion effects in field scale models.
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Summary Dispersion (or local mixing) degrades miscibility in miscible-flood displacements by interfering with the transfer of intermediate components that develop miscibility. Dispersion, however, also can improve oil recovery by increasing sweep efficiency. Either way, dispersion is an important factor in understanding miscible-flood performance. This paper investigates longitudinal and transverse local mixing in a finite-difference compositional simulator at different scales (both fine and coarse scale) using a 2D convection-dispersion model. All simulations were of constant-mobility and -density, first-contact miscible flow. The model allows for variations of velocity in both directions. We analyzed local (gridblock) concentration profiles for various miscible-displacement models with different scales of heterogeneity and permeability autocorrelation lengths. To infer dispersivity, we fitted an analytical 2D convection-dispersion model to the local concentration profile to determ...
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This paper investigates the non-equilibrium observed between the compositions of the produced phases in a series of multi-contact miscible displacements performed in the laboratory. These used a two-phase, threecomponent (Isopropyl alcohol/water/cyclohexene) liquid system that exhibits an upper critical point at ambient conditions. Both vaporising and condensing drives were performed in well-characterised homogenous glass-bead packs. The use of analogue fluids and bead-packs enabled visualisation of the displacements as well as the usual measurements of effluent composition against time and recovery. Non-equilibrium was observed in the effluent from both the condensing and vaporising experiments. This increased with flow-rate but appeared to be independent of the permeability and the length of the bead-pack. Further experiments investigating the influence of gravity on vertical displacements indicated that nonequilibrium may also be a function of the viscous to gravity ratio. Detailed simulation using a commercial compositional simulator was unable to predict this non-equilibrium unless the results were tuned to the experimentally observed effluent profiles using alpha factors. This is despite the fact that all PVT data, relative permeabilities and other pack properties were taken directly from the experiments. However good results were obtained from a layered model with the permeability distribution previously adjusted to match effluent data from a unit mobility ratio miscible displacement in the same pack. These results are consistent with physical dispersion being the underlying cause of the non-equilibrium. Viscous fingering was discounted due to the low mobility ratio (~2) of the displacements.
Water Resources Research, 2002
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Journal of Contaminant Hydrology, 2005
Capillary pressure/saturation data are often difficult and time consuming to measure, particularly for non-water-wetting porous media. Few capillary pressure/saturation predictive models, however, have been developed or verified for the range of wettability conditions that may be encountered in the natural subsurface. This work presents a new two-phase capillary pressure/saturation model for application to the prediction of primary drainage and imbibition relations in fractional wettability media. This new model is based upon an extension of Leverett scaling theory. Analysis of a series of DNAPL/water experiments, conducted for a number of water/intermediate and water/organic fractional wettability systems, reveals that previous models fail to predict observed behavior. The new Leverett-Cassie model, however, is demonstrated to provide good representations of these data, 0169-7722/$ -see front matter D as well as those from two earlier fractional wettability studies. The Leverett-Cassie model holds promise for field application, based upon its foundation in fundamental scaling principles, its requirement for relatively few and physically based input parameters, and its applicability to a broad range of wetting conditions. D
A pore-level screening study on miscible/immiscible displacements in heterogeneous models
Journal of Petroleum Science and Engineering, 2013
A comprehensive understanding of the role of reservoir heterogeneities induced by flow barriers and connate water on sweep efficiency of different EOR scenarios is rarely attended in the available literature. In this work, different miscible/immiscible EOR processes were conducted on various one-quarter five-spot glass micromodels incorporating small scale flow barriers. Microscopic and macroscopic observations revealed the reduction of sweep efficiency, premature breakthrough of displacing fluids, the severity of fingering at displacement front which leaves large amount of oil behind the flow barriers untouched, and significant increasing trend of oil recovery after breakthrough in presence of flow barriers. For the range of experiments performed here, the higher oil recovery is attained by polymer, hydrocarbon solvent,
The Areal Sweep Efficiency of the First-contact Miscible Displacements: An Experimental Approach
Petroleum Science and Technology, 2008
Solvent flooding using the water alternating gas (WAG) technique is very important for predicting the process performance. This technique has been employed in a number of oil fields. However, little data are available in the literature. Therefore, there is an immense need for the sweep efficiency data resulting from first-contact miscible flooding, particularly in view of conducting reservoir simulation studies. In this article, we conducted a series of WAG displacements through glass bead packs. A number of miscible WAG displacement tests were conducted at WAG ratios of 1:1, 1:2, and 2:1. Constant flow rates were used to mask the effects of capillary number on sweep efficiency. Experimental results revealed that the WAG ratio affects the sweep efficiency of the miscible flooding process. In addition, new correlations of areal sweep as function of mobility ratio at various WAG ratios were developed. The data provided can be useful to the oil industry in conducting analytical and numerical modeling studies of miscible WAG processes.