Pressure-volume-temperature Data Research Articles

Performance comparison of bubble point pressure from oil PVT data: Several neurocomputing techniques compared

Pressure–Volume–Temperature (PVT) characterization of a crude oil involves establishing its bubble point pressure, which is the pressure at which the first gas bubble forms on a fluid sample while reducing pressure at a stabilized temperature. Although accurate measurement can be made experimentally, such experiments are expensive and time-consuming. Consequently, applying reliable artificial intelligence (AI)/machine learning methods to provide an accurate mathematical prediction of an oil’s bubble point pressure from more easily measured characteristics can provide valuable cost and time savings. This paper develops and compares four neurocomputing models applying algorithms consisting of a Multilayer Perceptron (MLP), a Radial Basis Function trained with a Genetic Algorithm (RBF-GA), a Combined Hybrid Particle Swarm Optimization-Adaptive Neuro-Fuzzy Inference System (CHPSO-ANFIS), and Least Squared Support Vector Machine (LSSVM) tuned with a coupled simulated annealing (CSA) optimizer. Based on a comprehensive analysis, although the four proposed models yield acceptable outputs, the CHPSO-ANFIS model has the best performance with the average absolute relative deviation of 0.846, the standard deviation of 0.0126, the root mean square error of 43.21, and the correlation coefficient of 0.9902. These algorithms are deployed for the accurate estimation of the bubble point pressure from the giant Ahvaz oil field (Iran).

Thermodynamic analysis PVT equation of state definition and gas injection review along with case study in three wells of Iranian oil field

ABSTRACT The study aims to predict the physical properties of Iran crude oils using modified pressure-volume-temperature (PVT) equation of state. The modification was theoretically developed and then performed by using data of 30 black oil samples representing all active oil producing areas of Iran. The equation enables to predict the bubble-point pressure, oil formation volume factor, gas–oil ratio, oil density, crude oil gravity, gas gravity, and gas formation volume factor of black oils with average relative errors ranging from 0.01% to 10.713%. Calculation sensitivity of the proposed Peng-Robinson is determined by testing four oil samples collected from different locations in Iran and comparing the measured PVT properties with those calculated from Peng-Robinson. These evaluations show an excellent agreement between the measured properties and calculated ones. The estimation of reservoir liquid and gas properties from Peng-Robinson is often needed when detailed laboratory PVT data are not available.

NEW DERIVED CORRELATIONS FOR LIBYAN CRUDE OIL TO ESTIMATE BUBBLE-POINT PRESSURE

The key factor of all petroleum engineering calculation is the knowledge of the PVT (Pressure, Volume, Temperature) parameters, such as determination of oil and gas flowing properties, predicting production performance in the future, production facilities designing and enhanced oil recovery planning methods. Those PVT properties are ideally determined experimentally in the laboratory. However, some of these experimental data is not always available; consequently, empirical correlations are used to estimate them. Many researchers have been focusing on models for predicting reservoir fluid properties from the available experimental PVT data, such as reservoir pressure, temperature, crude oil API gravity, gas oil ratio, formation volume factor, and gas gravity. The present study compares between some of the available empirical PVT correlations for estimating the bubble point pressure of some Libyan crude oils based on 35 data point samples from different Libyan oil fields. In the second part of this study, a new correlation has been derived to predict the bubble point pressure using Eviews software and compares the output results of this new correlation with some derived correlations found in the literature using statistical analysis such as the Average Absolute Error (AARE). The results showed an AARE as low as 8.7%, for bubble point pressure estimated by this new derived correlation. These results are valid to compare to other driven empirical correlations that have been evaluated.

Geochemical factors controlling the phase behavior of Eagle Ford Shale petroleum fluids

Petroleum types in the Eagle Ford resource play span the range from black oil to dry gas and are produced along regional trends that are largely maturity controlled. A total of 61 shale samples covering all maturity zones were evaluated to document organic richness, organic matter type, and maturation characteristics using established geochemical parameters. Pyrolysis experiments were then performed to simulate the generation of petroleum fluids. Termed the “PhaseSnapShot” approach, one or more target wells with known fluid properties were used as reference; a match with that composition was made using next-formed fluids generated from the shale in a closely located well of slightly lower thermal maturity than the target well(s). Phase behavior predictions from the model were calibrated using a regional pressure–volume–temperature (PVT) database compiled from the public domain. The conceptual model that best matched the PVT data were comprised of two reactive components: (1) a mixture of kerogen and bitumen that generated petroleum within the low permeability shale matrix and (2) bitumen in zones of enhanced porosity within the matrix. The combined generation of gas from both of these components as well as the strong retention of C7+ fluids in the matrix during production were required to match the calibration data. Retention of oil was needed over a broad thermal maturity range (Rock-Eval Tmax release: 440°C –475°C). A key result of this forward model is that phase behavior and bulk compositional properties of hydrocarbons can be quickly and effectively predicted using mature shale samples as long as calibration data from PVT reports are available.

Advancements in Annular-Pressure-Buildup Mitigation for Thunder Horse Wells

SummaryA wide variety of annular-pressure-buildup (APB) -mitigation techniques has been deployed in the past 2 decades. In the early 2000s, BP focused efforts on the development and implementation of rupture disks, nitrified foam spacers, syntactic-foam modules, and vacuum-insulated tubing (VIT). Initiatives to simplify operations while maintaining well integrity have led to innovative techniques that expand the APB-mitigation toolkit.BP's Gulf of Mexico (GOM) Thunder Horse drilling team recently pursued three APB-mitigation techniques. One method is to fully cement the annulus, thereby removing the fluid that is subject to thermal expansion in a trapped annulus. A second method uses a qualified port collar to equalize pressure across a casing string. The third method focuses on better acquisition and use of mud pressure/volume/temperature (PVT) data for a more precise prediction of the APB-design loads.These methods and techniques have led to the removal of syntactic foam from some wells in the Thunder Horse field. The design change reduces installation time and operational complexity during well construction and abandonment.This paper provides a description and technical details concerning the planning and job execution for the fully cemented annulus and the use of port collars for pressure equalization. It also discusses the motivation behind acquiring PVT data specific to a particular mud system, and provides interpretation of laboratory data. The work may be useful for other operators as they plan and execute wells subject to the potential for APB.

Current Approaches in Prediction of PVT Properties of Reservoir Oils

PVT (pressure-volume-temperature) properties of reservoir fluids in the oil and gas industry constitute an integral part of the required data for a thorough study of the reservoir, optimally compilation of oil production and operation schemes. In the absence of PVT data that measured in laboratory conditions, empirical correlation is used to evaluate these properties. These correlations cannot be applied universally due to the differences of crude oil composition, the working condition of geographical and oil environment. In the article widespread correlations and models was investigated in the field of prediction of PVT properties of reservoir oil from different regions. Their accuracy and productivity was thoroughly analyzed too.

How Free Volume Does Influence the Dynamics of Glass Forming Liquids.

In this article we show that inverse free volume is a natural variable for analyzing relaxation data on glass-forming liquids, and that systems obey the general form, log(τ/τref) = (1/Vfree) × f(T), where f(T) is a function of temperature. We demonstrate for eight glass-forming liquids that when experimental relaxation times (log τ), captured over a broad pressure-volume-temperature (PVT) space, are plotted as a function of inverse free volume (1/Vfree), a fan-like set of straight line isotherms with T-dependent slopes ensues. The free volume is predicted independently of the dynamic results for each state point using PVT data and the Locally Correlated Lattice (LCL) equation of state. Taking f(T) ∝ 1/Tb, we show that, for each of the systems studied, only the single, system-dependent parameter, b, is required to collapse the fan of linear isotherms into a straight line. We conclude that log τ is a function of the combined variable, 1/(VfreeTb), and because it is linear, it allows us to write an explicit analytic expression for log τ that covers a broad PVT space.

Predictive model for gas and vapor sorption and swelling in glassy polymers: II. Effect of sample previous history

The solubility of various gases in several glassy polymers has been analyzed by the nonequilibrium thermodynamics for glassy polymers (NET-GP) framework, coupled with a lattice fluid equation of state model. Moreover, a simple rheological tool recently introduced for the a priori evaluation of the penetrant induced swelling is employed to predict the volumetric behavior of the solute/polymer mixture below Tg. Such model accounts for an additional nonequilibrium parameter for the description of polymer phase that represents its pseudoequilibrium compressibility, and it can be retrieved from pure component pressure–volume–temperature data below Tg. More in detail, the effect of polymer pretreatment and its prior history (e.g. annealing or conditioning by preswelling) on the resulting solubility behavior has been thoroughly analyzed and discussed, and the experimental data obtained for several penetrant/polymer couples have been well described by the present model.

An Experimental Study of Multiphase Behavior for n-Butane/Bitumen/Water Mixtures

Summary Steam/solvent coinjection has been studied and pilot tested as a potential method to improve steam-assisted gravity drainage (SAGD) for bitumen recovery. Reliable design of coinjection requires reliable pressure/volume/temperature (PVT) data for bitumen/solvent/water mixtures, which are scarce and fragmentary in the literature. The main objective of this research was to present a new set of PVT and multiphase data for n-butane/Athabasca-bitumen/water mixtures at pressures up to 10 MPa and temperatures up to 160°C. Experiments were conducted with a conventional PVT apparatus. The data presented include multiphase equilibria up to four coexisting phases and liquid densities for 100% bitumen, two mixtures of n-butane/bitumen, and one mixture of n-butane/bitumen/water. Liquid/liquid separation of hydrocarbons was experimentally observed at the n-butane concentration of 97 mol% in the n-butane/bitumen system with/without water, for a wide range of temperatures at operating pressures for expanding-solvent SAGD (ES-SAGD). This may indicate the limited solubility of n-butane in bitumen even when a high level of accumulation of n-butane takes place near a chamber edge in ES-SAGD for Athabasca bitumen. The multiphase transition that involves appearance/disappearance of the vapor phase was observed to occur near the vapor pressure of n-butane or its extension. Such phase transition occurs at a higher pressure in the presence of water, because of its vapor pressure, than in the absence of water at a given temperature. This is the first time four coexisting phases are reported for n-butane/Athabasca-bitumen/water mixtures at temperature/pressure conditions relevant to ES-SAGD.

A Review and Extension of Existing Consistency Tests for PVT Data From a Laboratory

SummaryAny calculation of the phase behavior of a reservoir fluid from the reservoir to the refinery requires prior knowledge of the fluid's physical properties. Because the necessary pressure–volume–temperature (PVT) experiments are not free of systematic and random errors, the engineer involved in using fluid models is advised to check the fluid properties determined by the laboratory before application in their simulation models. This paper is designed to provide a guideline for how to obtain reliable and consistent PVT data from a laboratory. In addition, it reviews and extends existing consistency checks with a critical focus on the Y-function. Its applicability is limited to the two-phase region of a reservoir fluid. As it turns out, the Y-function can be applied not only to the constant-composition experiment (CCE) of black oil (BO), but also for the same experiment with a gas-condensate (GC). Furthermore, we show that the Y-function is a useful tool for the evaluation of the differential-liberation experiment (DLE, BO) and the constant-volume depletion (CVD, GC). In all these cases, the shape of this function is close to a straight line. After the Y-function is properly set up, it is possible to estimate the quality of the CCE and the DLE for the BO case and CCE and CVD for the GC. The second part of the review is devoted to explaining the role of the solution gas in BO, because both the formation volume factor (FVF) Bo and the oil viscosity μo are affected by the amount of solution gas. Helpful functions for estimates and consistency checks are given. In addition, estimates for the isothermal compressibility and the isobaric expansion of oil are presented.

Microfluidic PVT--Saturation Pressure and Phase-Volume Measurement of Black Oils

Summary In this work, we present a small-scale pressure/volume/temperature (PVT) cell that allows for the measurement of saturation pressure and phase-volume ratio by use of only a few microliters of black-oil samples. This novel PVT measurement technique has been successfully tested on live samples at elevated pressure (86 MPa) and temperature (150°C). In the microfluidic PVT platform, the small microfluidic device performs the same function as the laboratory-scale pressurized visual PVT cell. At the heart of the microfluidic device, is a long and narrow capillary, densely packed in a serpentine shape, embedded on the device. The capillary is nearly 1 m long and has a total volume of 5 µL. The microfluidic device is fabricated with glass and silicon, which allow visual monitoring of a fluid sample at various pressures and temperatures. To acquire PVT data, the pressure in the capillary is systematically reduced to accurately detect the appearance of micron-sized gas bubbles in a sample at saturation pressure. Because of the small thermal mass of the device, the temperature of the sample can be changed rapidly, which enables the measurement of multiple saturation pressures in quick succession. Below the saturation pressure, the growing gas bubbles form a segmented gas/liquid distribution in the capillary. The lengths of the liquid and gas segments are measured in real-time with an automated image-capturing and analysis tool to determine the gas/liquid phase-volume ratio at a given pressure. Validation tests have proved this technique to be repeatable and feasible for rapid PVT measurements of black oils [gas/oil ratio (GOR) ranging from 102 to 143 m3/m3]. The results presented in this study demonstrate that the microfluidic PVT system can measure saturation pressure and phase-volume with data quality comparable to that of the conventional PVT method, however, with significantly smaller sample volume and faster turnaround. The microfluidic PVT system is demonstrated to have the potential to become a reliable and portable measurement platform.

The application of modified PVT data on the warpage prediction of injection molded part

The warpage of injection molded part strongly depends on the shrinkage property, which is highly dominant by the Pressure-Volume-Temperature (PVT) curves. Accurate description of PVT curves is essential for running the simulation of warpage. The standard PVT curves are measured at different pressure for the isotactic polypropylene, which are modified with the help of crystallizing curves obtained by the Differential Scanning Calorimetry (DSC) tests at different cooling rate. The user subroutine UEXPAN is coded to describe the modified PVT curves and implemented into the FEA model for warpage prediction in Abaqus. The simulated deflection of a plaque is performed and compared with the one measured by the coordinate measuring machine (CMM). It is concluded that the specific volume at high cooling rate varies slower with the temperature than that at low cooling rate and thus the predicted deflection with modified PVT data decreases significantly with increasing cooling rate. This numerical observation matches well with the experimental result. The warpage decreases when the crystallinity increases from 33 to 60 %. The plaque has the lowest peak deflection when the cooling rate is 60 °C/min. The system is built successfully for the warpage prediction of injection molded part.

Thermal equation of state of natural tourmaline at high pressure and temperature

Synchrotron-based in situ angle-dispersive X-ray diffraction experiments were conducted on a natural uvite-dominated tourmaline sample by using an external-heating diamond anvil cell at simultaneously high pressures and temperatures up to 18 GPa and 723 K, respectively. The angle-dispersive X-ray diffraction data reveal no indication of a structural phase transition over the P–T range of the current experiment in this study. The pressure–volume–temperature data were fitted by the high-temperature Birch–Murnaghan equation of state. Isothermal bulk modulus of K 0 = 96.6 (9) GPa, pressure derivative of the bulk modulus of $$K_{0}^{\prime } = 12.5 \;(4)$$ , thermal expansion coefficient of α 0 = 4.39 (27) × 10−5 K−1 and temperature derivative of the bulk modulus (∂K/∂T) P = −0.009 (6) GPa K−1 were obtained. The axial thermoelastic properties were also obtained with K a0 = 139 (2) GPa, $$K_{a0}^{\prime }$$ = 11.5 (7) and α a0 = 1.00 (11) × 10−5 K−1 for the a-axis, and K c0 = 59 (1) GPa, $$K_{c0}^{\prime }$$ = 11.4 (5) and α c0 = 2.41 (24) × 10−5 K−1 for the c-axis. Both of axial compression and thermal expansion exhibit large anisotropic behavior. Thermoelastic parameters of tourmaline in this study were also compared with that of the other two ring silicates of beryl and cordierite.

A New Oil Formation Volume Factor Correlation of Egyptian Crude Oils

Knowledge of reservoir fluid properties is very important in reservoir engineering calculations such as reserve estimates and numerical reservoir simulations. Laboratory measurements are the most dependable methods for pressure-volume-temperature (PVT) analysis of reservoir fluid properties. Under circumstances, the absences of such measurements are unavailable, hence, resorted to use empirical PVT correlations. Within the current research, a new correlation for estimating oil formation volume factor at bubblepoint pressure of Egyptian crude oils using nonlinear multiple regression technique has been developed. In developing the correlation, 162 PVT data sets from Egyptian crude oils were used. The data were collected from different fields in Egypt and covered a wide range of crude oils ranging from heavy to volatile oils. The data consisted of oils with oil formation volume factor at bubblepoint pressure ranging from 1.068 to 2.43 bbl/stb, o API of 17 to 46, solution gas oil ratio of 52 to 2254 scf/stb, gas gravity of 0.6 to 1.474 and temperature of 107 to 310 o F. The developed correlation was taken as a function of solution gas oil ratio, oil gravity, gas relative density and reservoir temperature. Statistical and graphical analyses have been used to evaluate the performance of the developed correlation. Correlation performance was also compared with published correlations. It was found that the new correlation estimates oil formation volume factor at bubblepoint pressure of Egyptian crude oils much better than the published ones. The obtained outcomes include an average relative error (ARE) of 0.06, an average absolute error (AARE) of 2 and coefficient of regression (R 2 ) of 0.98.In the current research, PVT data sets were collected from Egyptian reservoirs and regression analysis were used to obtain oil FVF correlation.

Thermodynamic scaling of molecular dynamics in supercooled liquid state of pharmaceuticals: Itraconazole and ketoconazole.

Pressure-Volume-Temperature (PVT) measurements and broadband dielectric spectroscopy were carried out to investigate molecular dynamics and to test the validity of thermodynamic scaling of two homologous compounds of pharmaceutical activity: itraconazole and ketoconazole in the wide range of thermodynamic conditions. The pressure coefficients of the glass transition temperature (dT(g)/dp) for itraconazole and ketoconazole were determined to be equal to 183 and 228 K/GPa, respectively. However, for itraconazole, the additional transition to the nematic phase was observed and characterized by the pressure coefficient dT(n)/dp = 258 K/GPa. From PVT and dielectric data, we obtained that the liquid-nematic phase transition is governed by the relaxation time since it occurred at constant τ(α) = 10(-5) s. Furthermore, we plotted the obtained relaxation times as a function of T(-1)v(-γ), which has revealed that the validity of thermodynamic scaling with the γ exponent equals to 3.69 ± 0.04 and 3.64 ± 0.03 for itraconazole and ketoconazole, respectively. Further analysis of the scaling parameter in itraconazole revealed that it unexpectedly decreases with increasing relaxation time, which resulted in dramatic change of the shape of the thermodynamic scaling master curve. While in the case of ketoconazole, it remained the same within entire range of data (within experimental uncertainty). We suppose that in case of itraconazole, this peculiar behavior is related to the liquid crystals' properties of itraconazole molecule.

Pressure‐volume‐temperature and glass transition behavior of silica/polystyrene nanocomposite

ABSTRACTThe pressure‐volume‐temperature (PVT) behavior and glass transition behavior of a 10 wt % silica nanoparticle‐filled polystyrene (PS) nanocomposite sample are measured using a custom‐built pressurizable dilatometer. The PVT data are fitted to the Tait equation in both liquid and glassy states; the coefficient of thermal expansion α, bulk modulus K, and thermal pressure coefficient γ are examined as a function of pressure and compared to the values of neat PS. The glass transition temperature (Tg) is reported as a function of pressure, and the limiting fictive temperature (Tf′) from calorimetric measurements is reported as a function of cooling rate. Comparison with data for neat PS indicates that the nanocomposite has a slightly higher Tg at elevated pressures, higher bulk moduli at all pressures studied, and its relaxation dynamics are more sensitive to volume. The results for the glassy γ values suggest that thermal residual stresses would not be reduced for the nanocomposite sample studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1131–1138

Rapid method for the determination of solution gas-oil ratios of petroleum reservoir fluids

Accurate determination of pressure-volume-temperature (PVT) properties of petroleum reservoirs is essential in material balance calculations, inflow performance, well-test analysis, reservoir simulation, etc. Ideally, those data should be obtained experimentally; however, experimental measurements require accurate and enough sampling, and are time consuming, expensive and tedious. Therefore, seeking for a simple, reliable and accurate model for prediction of PVT properties of petroleum systems is of a vital importance. In this communication, a large PVT data bank, covering a wide range of thermodynamic conditions was collected from variety of geographical locations around the world. Afterward, gene expression programming (GEP) was employed to develop a universal model for solution gas: oil ratio. The proposed model is a function of bubble point pressure, gas specific gravity, and oil API gravity, and has a very simple format with only one tuning parameter. The proposed model was compared to both explicit and implicit models available in literature for prediction of solution gas: oil ratio, using statistical and graphical error analyses. The results of this study indicate that the proposed model is more accurate, reliable and efficient compared to all other published correlations.

Volume Shrinkage and Cure Kinetics in Carboxyl-Terminated Poly(butadiene-co-acrylonitrile) (CTBN) Modified Epoxy/Clay Nanocomposites

The role of carboxyl-terminated poly(butadiene-co-acrylonitrile) (CTBN) liquid rubber and reactive surfactant modified nanoclay on the volume shrinkage during cure reaction and cure kinetics of epoxy/anhydride system in the presence of a catalyst was studied using Pressure-Volume-Temperature (PVT) measurements and real time FTIR spectroscopic analysis, respectively. The dilution effect of CTBN and catalytic effect of clay modifier on the epoxy/anhydride reaction reflected in the volume shrinkage behavior of CTBN modified epoxy/clay nanocomposites (epoxy/clay/CTBN hybrid) during cure. The kinetics of cure was studied based on the conversions derived from PVT data assuming a linear relation between network formation and volume shrinkage. The consumption of epoxy band (913 cm−1) during cure obtained from the real time FTIR spectroscopic analysis was employed to compare the effect of both CTBN and nanoclay on the cure kinetics. In epoxy/clay/CTBN hybrid, during the initial stage of cure the catalytic activity of the clay modifier controls the cure rate, and at the final stage the phase separated CTBN obstruct the diffusion of reactive sites to slows down the conversion rate. The Tg obtained from DSC analysis of the cured samples confirmed the observed shrinkage and cure behavior.

Equations of state of ice VI and ice VII at high pressure and high temperature.

High-pressure H2O polymorphs among which ice VI and ice VII are abundant in the interiors of large icy satellites and exo-planets. Knowledge of the elastic properties of these pure H2O ices at high-temperature and high-pressure is thus crucial to decipher the internal structure of icy bodies. In this study we assess for the first time the pressure-volume-temperature (PVT) relations of both polycrystalline pure ice VI and ice VII at high pressures and temperatures from 1 to 9 GPa and 300 to 450 K, respectively, by using in situ synchrotron X-ray diffraction. The PVT data are adjusted to a second-order Birch-Murnaghan equation of state and give V0 = 14.17(2) cm(3) mol(-1), K0 = 14.05(23) GPa, and α0 = 14.6(14) × 10(-5) K(-1) for ice VI and V0 = 12.49(1) cm(3) mol(-1), K0 = 20.15(16) GPa, and α0 = 11.6(5) × 10(-5) K(-1) for ice VII.

Predictive model for gas and vapor solubility and swelling in glassy polymers I: Application to different polymer/penetrant systems

An extensive analysis is performed for the use of a model recently introduced for sorption induced volume dilation in glassy polymers, which can be combined with the nonequilibrium lattice fluid model (NELF) for the description of gas and vapor solubility in glassy polymers in a wide temperature range below the glass transition, from dry to fully plasticized conditions. The procedure extends the capability of previous versions of NELF model, as it refers to correlation and prediction of solubility of vapors and swelling agents. To this aim, the model counts on an additional out-of-equilibrium parameter for the polymeric species that interprets its pseudoequilibrium compressibility, and it can be retrieved from the analysis of pure component pressure–volume–temperature data below Tg. The examples discussed in this work show that the overall procedure is highly reliable and addresses the key properties of the system for the direct interpretation of the effect of temperature, solute fugacity and state of glassy polymers on pseudoequilibrium volume swelling and solute content.