PVT Measurements Research Articles

Origin of ργ/T scaling of primary and secondary conductivity relaxation times in mixture of water with protic ionic liquid.

Murali et al. [J. Phys. Chem. Lett., 2024, 15, 3376-3382] made ambient and high pressure dielectric measurements of a supercooled aqueous mixture of an acidic ionic liquid to find the presence of the primary (σ) conductivity relaxation together with the secondary (ν) conductivity relaxation originating from the water clusters confined by the cations and anions with relaxation times τσ and τν respectively. From the isothermal and isobaric conductivity relaxation data found on varying thermodynamic conditions (i.e. T and P) at constant τσ are the invariance of (i) the frequency dispersion or the Kohlrausch function exponent (1 - n) of the primary conductivity relaxation, and (ii) the ratio of the primary and secondary conductivity times, τσ/τν. This co-invariance of τσ, τν, and (1 - n) at constant τσ was observed before in non-aqueous ionic liquids, but it is found for the first time in aqueous ionic liquids. The new data together with PVT measurements enable Murali et al. to show additionally that both τσ and τν are functions of ργ/T with a single exponent γ = 0.58. The Coupling model is the only theory predicting the co-invariance of τσ, τν, and (1 - n) as well as the ργ/T scaling of both τσ and τν. It is applied herein to address and explain the data of the ionic liquid-water mixture.

High-pressure properties of type V Natural Deep Eutectic Solvents: The case of menthol: thymol

This work reports a study on the properties of Menthol: Thymol 1: 1 type V Natural Deep Eutectic Solvent under high pressure conditions (up to 600 bar). The experimental PVT measurements allowed to calculate the most relevant thermophysical properties and its relationships with intermolecular forces and nanostructuring. PC-SAFT equation of state was considered for treating experimental thermodynamic data using a two-components approach, thus leading to a successful prediction of properties considering a single temperature-independent binary interaction parameter. The considered DESs shows atype I global phase behavior, with extremely narrow phase loop and low volatility. Classical Molecular Dynamics simulations provided a detailed nanoscopic picture of the fluid structuring and dynamics upon compression, with results showing minor changes in the nature and extension of hydrogen bonding and the main structural and dynamics features being maintained in the considered pressure range. The combined experimental and modelling study allowed a detailed characterization of the properties of this fluid under high pressure conditions.

The role of the critical compressibility factor in the equation of state for the critical fluid

Based on the literature data of PVT measurements, the amplitudes of the equations of the critical isotherm D0(Zk), the critical isochore Г0(Zk), the phase boundaries В0(Zk) are expressed in terms of the critical factor of compressibility of the substance Zk=PkVk/RTk in the entire fluctuation region near the critical point. By doing so, a phenomenological method has been used for calculating the values of the critical exponents of the fluctuation theory of phase transitions based on the introduction of small parameters into the equations of the fluctuation theory. 
 It has been shown that, within the limits of the PVT measurement errors, these dependences D0(Zk) and В0(Zk) on the compressibility factor are linear, and Г0 practically does not depend on the compressibility factor Zk.
 The relationship of these amplitudes with the amplitudes a and k of the linear model of the system of parametric scale equations of state of substance near the critical point has been established. It has been shown that the dependences k(Zk) and а(Zk) are also linear in the entire fluctuation region near the critical point. The obtained dependences k(Zk) and а(Zk) agree with the known relationship between the amplitudes of the critical isotherm D0(Zk), critical isochore Г0(Zk), phase boundaries В0(Zk) Aerospace Institute of the National Academy of Sciences of Ukrainewithin the framework of the system of parametric scaling equations.
 The relations а(Zk), k(Zk) make it possible, on the basis of a linear model of the system of parametric scale equations of state of substance, to determine such important characteristics of the critical fluid as the temperature and field dependences of the correlation length Rc(T,m) and the fluctuation part of the thermodynamic potential Ф(T,m) in the entire fluctuation region near the critical point.
 Then, based on the form of the fluctuation part of the thermodynamic potential Ф(T,m)~Rc(T,m)-3, the results obtained allow one to calculate the field and temperature dependences of the thermodynamic quantities for a wide class of molecular liquids in the close vicinity of the critical point (DP<10-3, Dr<10-2, t<10-4), where precision experiments are significantly complicated, and its can also be used when choosing the conditions for the most effective practical application of the unique properties of the critical fluid in the newest technologies.

High-temperature and high-pressure PVT measurements and derived thermodynamic properties of geothermal fluids from East Turkey

As a part of our long-term continuing program of experimental study of the thermodynamic and transport properties of geothermal fluids, the high-temperature and high-pressure densities and vapor-pressures of two natural geothermal fluids from East Turkey Geothermal Field (Keklik Mağarasi and Afyon geothermal wells) have been measured over the temperature range from (274 to 413) K and at pressure up to 100 MPa. The measurements of the PVT properties were made using vibrating tube densitometer (VTD) DMA HPM (AntonPaar, Austria). The vapor-pressure was measured using absolute static method. The standard uncertainty of the density, pressure, and temperature measurements is estimated to be (0.0001 to 0.0003 depending on T and P ranges), 0.001, and 10 mK, respectively. Measured values of high-temperature and high-pressure density (PVT data) were used to estimate Tait’s parameters (c and B) and their temperature dependence. Developed Tait-type equation of state has been be used to calculate other derived key thermodynamic properties (βS,βT,αP,γV,H, S, U, u,CP,CV) of the geothermal waters at high-temperatures and high-pressures, which are very important for modeling of the geothermal reservoirs and optimization of the geothermal energy production processes. The measured values of PVT property of the geothermal water samples were also used to check and confirm reliability and accuracy of the high-temperature and high-pressure prediction method for geothermal fluids using only densities at atmospheric pressure and room temperature.

Transient measurement and modeling of integrated capillary viscometer for live oils at high temperatures with volumetric constraints

The viscosity of oils at reservoir conditions whether under natural depletion conditions or under induced conditions (i.e. EOR/IOR) is one of the key parameters for the dynamics of flow in porous media, and it has direct impact on the economically recoverable volumes as well as transportation problems where the fluids can get exposed to potentially wide range of temperatures. It becomes even more essential measurement for thermal based EOR techniques including high temperature steam injection or in-situ upgrading techniques due to strong (exponential) dependency of viscosity to temperature. Unfortunately, viscosity measurements for such applications suffer with the two key challenges. First, most commercial and research labs could measure viscosities up to 200 °C (while the application considered may induce temperatures as high as 300 °C beyond which most naturally occurring hydrocarbons starts decomposing). And second, these measurements are based on steady-state conditions, requiring significant volumes of oil samples. However, the available volume of oil samples for such applications may be very small for various reasons, including emulsions leading to very low useful volumes, cost of sampling, or inheritance of candidate samples from other laboratory processes, such as but not limited to core-flooding or reactive transport experiments.Therefore, in this work, we present a novel but simple technique to overcome these challenges by using simple capillary device that could be integrated to any system that requires charging and/or charging the candidate fluids such as PVT-cells, pressurized vessels that could be operated up to 300 °C or higher. Such integration utilizes the charging of fluids to the cell for viscosity measurements, leading to the following advantages:(i) it requires no additional volume of oil for viscosity measurements, and also saves the operational time and cost(ii) it could produce viscosity data at higher temperatures that are desired for in-situ upgrading or thermal EOR, even small amounts of particulates evolve in the bulk phase(iii) it ensures that the viscosity and PVT measurements are performed on the same sample eliminating the potential sample to sample variations.(iv) the proposed approach along with the developed methodology paves the way for a the implementation of unsteady in-line measurement of viscosities for pressurized systems. This includes not only lab processes, but also the downhole sampling where the method could be implemented in sampling devices.The technique proposed here is based on transient measurements and modeling of capillary viscometer, where pressure at the end points and flow rate through the capillary tube may vary with time (which is the most realistic conditions for variable back pressure systems or systems with frictional pistons). In addition to the experimental process, necessary mathematical model and interpretative analysis tools to quality check, assessment of the experimental data (and the establishment of the range of validity and limitations) are derived from first principals (bottom-up approach) using Navier-Stokes equations.

Saturated pressure and vapor-phase pvT measurements of 1,1-difluoroethene (R1132a)

This work presents 24 vapor pressures and 131 vapor-phase pvT properties for 1,1-difluoroethene (R1132a) measured using an isochoric apparatus. This fluid is a hydrofluoroolefin with a GWP less than 3 and it is considered to be a potential component for low-GWP refrigerant mixtures for ultralow temperature applications. The saturated pressure data were obtained in the temperature range from (223.15 to 280.65) K and pressure range from (0.471 to 2.675) MPa. The vapor-phase pvT measurements were performed in the temperature range from (223.15 to 303.15) K, pressure range from (0.312 to 2.340) MPa, and specific volume range from (0.013226 to 0.086770) m3 kg−1. The saturated pressure data were compared with the experimental values available in literature and fitted to extended Antoine-type and Wagner-type vapor-pressure correlations. The vapor-phase pvT data were compared with the values available in literature. In addition, the pvT properties were used to develop a truncated virial equation of state.

Determining of reservoir fluids properties using PVTP simulation software- a case study of buzurgan oilfield

The measurement of oil reservoirs and their performance with hydrocarbon reservoirs is used to distinguish the properties of reservoir fluids, which is significant in various reservoir studies. As a result, in the various oil industries, adopting the appropriate methods to obtain accurate property values is very important. The current paper is about a case study of the BUZURGAN Oilfield and how the PVTp software was used to predict phase activity and physical properties. To understand the properties of fluids for the reservoir and phase behavior, the black oil model and the equation of state (EoS) model are used. (Glaso) correlation is used to calculate the bubble point strain, solubility, and formation volume factor. The Beal's correlation was also used to measure viscosity, while the equation of state (EoS) model was used to determine phase behavior and density. Furthermore, the properties of PVT were discovered using the software, and the results were compared to laboratory analysis of PVT, with suitable models being displayed. According to the findings, the used model has the highest saturation pressure, which was chosen for use in reservoir management processes and the preparation of a geological model to reflect the field later. It is clear that the program is appropriate due to the accurate dependence of PVT measurements on laboratory tests in the case that tests are required during the reservoir's productive existence.

Development the models of oil Formation volume factor using artificial neural networks and fuzzy logic models

The oil formation volume factor with high accuracy method is a key role in the petroleum industry due to the wide use of it in the petroleum industry. It is readily obtained from laboratory PVT measurements or may be calculated from correlations such as Vasquez. Nevertheless, these measurements are either not available, or very costly to require. Thus, there is an essential need for a reliable method for obtaining the oil formation volume factor. The aim of this paper is predicting the oil formation volume factor using Artificial Neural Networks (ANN) and Fuzzy Logic (FL) tools. It is worth noticing that a data set consisting 800 of laboratory measurements on oil formation volume factor was gathered from different published resources. The paper also will use the current available models presented in the literature for predicting the oil formation volume factor and compare the average percent error of these models with the new base models. The results obtained depicted that new models were able to find the oil formation volume factor with higher accuracy than the current models for predicting oil formation volume factor. It is conspicuous results that the Artificial Neural Networks (ANN) model with coefficient 0.994 and Fuzzy Logic (FL) with coefficient 0.9993 provide the oil formation volume factor. The new developed models from the ANN and Fl models outperformed the prior models for the oil formation volume factor. It is obviously observed that the new models can be used to predict the oil formation volume factor with a high accuracy as compared with the other models used to be calculated from correlations such as Vasquez and Beggs.

PVT Measurements of the H2–CO2–CH4–CO–H2O System at 740–939 K and 18.1–34.7 MPa with an Isochoric Apparatus and the Development of a Virial Equation of State

Modeling the pVT properties of hydrogen mixtures at high temperatures is significant for the development of relevant production and utility systems. In this work, pVT measurements are reported for ...

PVT properties variation with depth in carbonate reservoirs: a case study

PVT properties of a hydrocarbon reservoir, in addition to estimate oil and gas in place, are required for optimum dynamic reservoir management. In carbonate reservoirs, it is more important as reservoir’s fluid properties usually vary laterally or/and vertically. In this paper, summary results of a study which carried out on the reported PVT properties of reservoir ‘A’ are presented. Reservoir ‘A’ is a real oil carbonate reservoir which suffers from variation of PVT properties. The oil gravity and GOR (gas-oil ratio) in this reservoir are reported to be in the range of 23°–36° API and 300–1400 SCF/STB (Standard Cubic Feet/Stock Tank Barrel), respectively. These wide ranges of PVT properties raised questions about the accuracy and consistency of PVT laboratory test results, FBDST (Full Bore Drill Stem Test) measured data and reservoir characterization, such as effect of seismic recognized faults and the validity of laboratory PVT measurements which conducted on the reservoir fluid samples gathered from adjacent wells in one zone. So, an extensive, systematic study has been conducted on the available fluid data to check the validity of data and find out an acceptable, logical hypothesis about PVT variation across the reservoir, vertically and/or laterally. This study reveals that the reported laboratory measured PVT analysis, oil API gravity and GOR (gas oil ratio) measured in well tests campaign are valid. The PVT variation is dominantly vertical owing to compositional gravity segregation due to relatively high thickness of reservoir, about 300 m (984 ft). It is also distinguished that seismic detected faults (if exist) do not act as barriers at least at geological time.

PVT and Thermal-Pressure Coefficient Measurements and Derived Thermodynamic Properties of 2-Propanol in the Critical and Supercritical Regions

PVT properties and the thermal-pressure coefficient, $$\gamma_{\text{V}} = \left( {\partial P/\partial T} \right)_{\text{V}}$$ , of 2-propanol have been simultaneously measured in the near- and supercritical regions using high-temperature and high-pressure nearly constant-volume piezo-calorimeter. Measurements were made along 9 liquid and 3 vapor isochores between (234.3 and 697.69) kg·m−3 and at temperatures from (317.17 to 522.36) K at pressures up to 6.05 MPa. For each measured isochore ( $$\rho$$ ), the values of phase transition temperature ( $$T_{S}$$ ) and pressure ( $$P_{S}$$ ) at the liquid–gas phase equilibrium curve have been determined using the isochoric $$P - T$$ break point and thermal-pressure coefficient abruptness techniques. The measured saturated liquid ( $$\rho^{\prime}_{S}$$ ) and vapor ( $$\rho^{\prime\prime}_{S}$$ ) densities near the critical point and thermal-pressure coefficient abruptness disappearance were used to estimate the values of the critical parameters ( $$T_{C}$$ = 508.72 K, $$P_{C}$$ = 4.840 MPa, and $$\rho_{C}$$ = 268.82 kg·m−3) of 2-propanol. The expanded uncertainty of the pressure ( $$P$$ ), density ( $$\rho$$ ), and thermal-pressure coefficient ( $$\gamma_{\text{V}}$$ ) measurements at the 95 % confidence level with a coverage factor of k = 2 are estimated to be 0.05 %, 0.16 %, and 1.5 %, respectively. Scaling-type critical anomaly of the asymptotic behavior of thermal-pressure coefficient in the immediate vicinity of the critical point was experimentally observed. The measured pressures ( $$PVT$$ ) and thermal-pressure coefficients ( $$\gamma_{\text{V}} VT$$ ) have been used to calculate of the other key thermodynamic properties such as internal pressure ( $$P_{\text{int}}$$ ), enthalpy ( $$\Delta H_{vap}$$ ) and entropy ( $$\Delta S_{vap}$$ ) of vaporization, saturation ( $$C_{\text{sat}}$$ ), isobaric ( $$C_{\text{P}}$$ ), and isochoric ( $$C_{\text{V}}$$ ) heat capacities.

Dynamic Compression Induced Solidification.

This study presents a method for the determination of the dynamic pressure-dependent solidification of polycarbonate (PC) during flow using high pressure capillary rheometer (HPC) measurements. In addition, the pressure-dependent solidification was determined by isothermal pressure-volume-temperature (pvT) measurements under static conditions without shear. Independent of the compression velocity, a linear increase of the solidification pressure with temperature could be determined. Furthermore, the results indicate that the relaxation time at a constant temperature and compression rate can increase to such an extent that the material can no longer follow within the time scale specified by the compression rate. Consequently, the flow through the capillary stops at a specific pressure, with higher compression rates resulting in lower solidification pressures. Consequently, in regard to HPC measurements, it could be shown that the evaluation of the pressure via a pressure hole can lead to measurement errors in the limit range. Since the filling process in injection molding usually takes place under such transient conditions, the results are likely to be relevant for modelling the flow processes of thin-walled and microstructures with high aspect ratios.

Process dependence of pressure-specific volume-temperature measurement for amorphous polymer: Acrylonitrile-butadiene-styrene

The process dependence of pressure-specific volume-temperature (pvT) measurement for an amorphous polymer, acrylonitrile-butadiene-styrene (ABS), was investigated. The influences of different measurement processes (heating, cooling, compression, and decompression with different rates) were considered in the pvT measurements. The pvT measurements of isobaric cooling and heating with different cooling and heating rates (2, 5, and 10 °C/min) and isothermal compression and decompression with different compression and decompression rates (up to 920 bar/s) were conducted. The testing temperature ranged between 40 and 230 °C and the pressure ranged between 20 and 2200 bar. The obtained results demonstrated that the pvT diagram will be significantly different depending on the direction in which the pressure or temperature is changing and also on the rate of the change. Isobaric pvT diagrams are different between cooling and heating. Fast cooling accelerates phase transitions, while fast heating reverses. Specific volume at the same pressure and temperature in decompression process is lower than that in compression. Compression and decompression leads to different pvT curves. Compression and decompression rates have different effects on specific volume in different states.

Multiscale modeling of compartmentalized reservoirs using a hybrid clustering-based non-local approach

Representing the reservoir as a network of discrete compartments with neighbor and non-neighbor connections is a fast, yet accurate method for analyzing oil and gas reservoirs. Automatic and rapid detection of coarse-scale compartments with distinct static and dynamic properties is an integral part of such high-level reservoir analysis. In this work, we present a hybrid framework specific to reservoir analysis for an automatic detection of clusters in space using spatial and temporal field data, coupled with a physics-based multiscale modeling approach.A novel and rigorous non-local formulation for flow in porous media is presented, in which the reservoir is represented by an adjacency matrix describing the connectivities of comprising compartments. We automatically divide the reservoir into a number of distinct compartments, in which the direction-dependent multiphase flow communication is a function of non-local phase potential differences. Our proposed clustering framework begins with a mixed-type raw dataset which can be categorical/numerical, spatial/temporal, and discrete/continuous. The dataset can contain noisy/missing values of different data types including but not limited to well production/injection history, well location, well type, geological features, PVT measurements, perforation data, etc. Unsupervised clustering techniques suited to the input data types (e.g. k-prototypes, spectral, Gaussian Mixtures, and hierarchical clustering), and appropriate distance measures (such as Euclidean distance, soft dynamic time warping, and mode) are used. The input data is standardized, and upon convergence check, the best clustering representation is obtained. Finally, Support-Vector-Machine technique is utilized in the kernel space to trace a demarcating hyperplane for the clusters.In a specific case study reported here, the proposed workflow is applied to a major field with a couple of hundreds of wells with more than 40 years of production history. Leveraging the fast forward model, an efficient ensemble-based history matching framework is applied to reduce the uncertainty of the global reservoir parameters such as inter-blocks and aquifer-reservoir communications, fault transmissibilities, and block-based oil-in-place. The ensemble of history matched models are then used to provide a probabilistic forecast for different field development scenarios. In addition, the clustering framework enables us to treat missing data and use the augmented dataset for improving the clustering accuracy.In summary, in this work a novel hybrid approach is presented in which we couple a physics-based non-local modeling framework with data-driven clustering techniques to provide a fast and accurate multiscale modeling of compartmentalized reservoirs. This research also adds to the literature by presenting a comprehensive work on spatio-temporal clustering for reservoir studies applications that well considers the clustering complexities, the intrinsic sparse and noisy nature of the data, and the interpretability of the outcome.

Density Data of Two (H2 + CO2) Mixtures and a (H2 + CO2 + CH4) Mixture by a Modified Burnett Method at Temperature 673 K and Pressures up to 25 MPa

The PVT properties of the (H2 + CO2) mixtures and the (H2 + CO2 + CH4) mixtures in the supercritical region of water are significant for making full use of the gas mixtures in the coal and supercritical water gasification. We report PVT measurements of the (0.6005 H2 + 0.3995 CO2), (0.6992 H2 + 0.3008 CO2), and (0.6026 H2 + 0.1948 CO2 + 0.2026 CH4) mixtures (all in mole fractions) at temperature 673 K and pressures of (0.5 to 25) MPa, measured by a modified Burnett method. The upper bounds of the expanded uncertainties at 95% confidence are 0.2 K for temperature, 0.015·p for pressure, and 0.008·ρ for density. The density data were compared with those predicted using the GERG-2008 equation of state. The deviations between the calculated and experimental data are not more than 0.021·ρ. Furthermore, the densities were found in accordance with the weighted average of the components’ existing equations of state using their mole fractions within 0.0076·ρ for all of the mixtures in this work. The second and thir...

Diffusivity of Carbon Dioxide in Aqueous Solutions under Geologic Carbon Sequestration Conditions.

Accurate assessment of the long-term security of geologic carbon sequestration requires knowledge of the mobility of carbon dioxide in brines under pressure and temperature conditions that prevail in subsurface aquifers. Here, we report Raman spectroscopic measurements of the rate of CO2 diffusion in water and brines as a function of pressure, salinity, and concentration of CO2. In pure water at 50 ± 2 °C and 90 ± 2 bar, we find the diffusion coefficient, D, to be (3.08 ± 0.03) × 10-9 m2/s, a value that is consistent with a recent microfluidic study but lower than earlier PVT measurements. Under reservoir conditions, salinity affects the mobility of CO2 significantly and D decreased by 45% for a 4 M solution of NaCl. We find significant differences of diffusivity of CO2 in brines (0-4 M NaCl), in both the absolute values and the trend compared to the Stokes-Einstein prediction under our experimental conditions. We observe that D decreases significantly at the high CO2 concentrations expected in subsurface aquifers (∼15% reduction at 0.55 mol/kg of CO2) and provides an empirical correction to the commonly reported D values that assume a tracer concentration dependence on diffusivity.

PVT, saturated liquid density and vapor-pressure measurements of main components of the biofuels at high temperatures and high pressures: Methyl palmitate

PVT, saturated liquid density and two-phase (vapor-pressure) properties of one of the main component of the biofuel (methyl palmitate), produced from a soybean, have been measured. One-phase PVT measurements were made for ten liquid and four vapor isochores between (85.2 and 811.7) kg·m−3over the temperatures range from (300 to 443) K using a constant-volume piezometer technique. The vapor-pressures (PS,TS) of the methyl palmitate were measured in the temperature range from (300 to 501) K. The combined expanded uncertainty of the density, ρ, pressure, P, and temperature, T, measurements at 95% confidence level with a coverage factor of k = 2 is estimated to be 0.1%, (0.15–0.5)% depending on temperature and pressure ranges, and 15 mK, respectively. We have critically assessed all of the reported density data at atmospheric pressure and at high-pressures and vapor-pressures together with the present results for their internal thermodynamic consistence to carefully select primary data to fit reference correlations for ρ0(T) and vapor-pressure PS(T). The measurements were concentrated in the two-phase region to accurately determine vapor-pressures and in the immediate vicinity of the phase-transition temperatures to precisely determine the phase boundary properties (PS,TS,ρS) on the liquid + gas equilibrium curve. The liquid-gas phase transition temperatures (TS) for seven liquid isochores of (711.9, 766.8, 774.5, 782.3, 795.00, 803.40, and 811.70) kg·m−3were accurately obtained using the isochoric (P-T) break point technique. The measured values of the vapor-pressures and saturated liquid densities were fitted to Wagner-type vapor-pressure equation and complete scaling model, respectively. The values of the critical parameters (PC,TC,ρC) were estimated using vapor-pressure and liquid-gas coexistence curve data. The correlation for the density at atmospheric pressure, ρ0(T), together with the present and reported high-pressure density measurements (ρ,P,T) were used to develop two-parametric (c and B) and theoretically based Tait-type equation of state.

Thermodynamic characterization of polymers

The central objective of this work is the presentation of a novel simple method for the characterization of polymers as regards their thermodynamic behavior in bulk phases and interfaces. For this purpose, LSER (Linear Solvation Energy Relationships) type molecular descriptors and polymer surface energies are derived, primarily, from Inverse Gas Chromatography (IGC) and contact angle measurements for a number of common polymers. The interconnection of these descriptors with the more familiar equation-of-state scaling constants from PVT measurements is explored. The characteristic LSER descriptors are used for the prediction of polymer – polymer miscibility as well as for handling IGC data for multicomponent systems. Emphasis is given on hydrogen-bonded polymer systems. As shown by a variety of examples, the efficiency and versatility of the method are particularly promising. The broader perspectives of this unified approach to solution thermodynamics are discussed.

Development of empirical correlation for DME-partitioning between brine and crudes for enhanced waterflooding applications

Dimethyl ether (DME) is considered to be a potential EOR agent for enhanced waterflooding. Due to first contact miscibility in hydrocarbons and partial solubility in water/brine, it partitions preferentially into the hydrocarbon phase upon contact when DME-brine solution is injected into the reservoir. As a result, the residual oil swells and its viscosity is reduced. The amount of swelling and viscosity-reduction depend on the extent of DME partitioning and its availability. Therefore, the estimation of the DME-partitioning coefficient (KDME) is crucial to evaluate and understand the performance of DME-enhanced waterflooding (DEW) at reservoir or lab/pilot-scale. In general, this coefficient is a function of several factors including the compositional characteristics of the oil, reservoir pressure-temperature conditions and the salinity of the formation brine. In this study, we perform extensive analysis on the sensitivity of KDME with respect to these factors using Peng-Robinson (PR78) EOS with Huron-Vidal (HV) mixing rules that we calibrated with experimental data. We also discuss the predictive capability of EOS models used in literature to characterize phase behavior of DME-brine-oil mixture. Finally, using all the information available, we develop an empirical correlation to estimate KDME in brine and hydrocarbons that can be utilized for future screening studies in which none or very limited PVT measurements with DME are available.

New correlations for prediction of saturated and undersaturated oil viscosity of Arabian oil fields

New correlations for saturated and undersaturated oil viscosity were developed for Saudi Arabian crude oil. The data consist of 79 and 71 experimental measurements of saturated and undersaturated crude oil viscosity, respectively, at reservoir conditions. Other PVT measurements above and below bubble point pressure are also included. The new correlations were developed using genetic programming approach. The new models were developed and tested using linear genetic programming (GP) technique. The models efficiency was compared to existing correlations. Average absolute relative deviation, coefficient of correlation, and crossplots were used to evaluate the proposed models, and their outputs indicate the accuracy of the GP technique and the superiority of the developed models in comparison with the commonly utilized models tested.