scholarly journals Prediction of asphaltene precipitation upon injection of various gases at near-wellbore conditions: A simulation study using PC-SAFT EoS

2019 ◽  
Vol 74 ◽  
pp. 63 ◽  
Author(s):  
Saba Mahmoudvand ◽  
Behnam Shahsavani ◽  
Rafat Parsaei ◽  
Mohammad Reza Malayeri
Keyword(s):  
Phase Behavior ◽  
Oil Recovery ◽  
Gas Injection ◽  
Drop Out ◽  
Maximum Point ◽  
Asphaltene Precipitation ◽  
Wide Range ◽  
Tertiary Oil Recovery ◽  
The Impact ◽  
Oil Type

The depletion of oil reservoirs and increased global oil demand have given impetus to employ various secondary and tertiary oil recovery methods. Gas injection is widely used in both secondary and tertiary modes, though the major problem associated with this process is the precipitation and deposition of asphaltene, particularly at near-wellbore conditions. In-depth knowledge of asphaltene phase behavior is therefore essential for the prediction of asphaltene precipitation. Previous studies reported the impact of gas injection on asphaltene phase behavior, but the knowledge of precipitation of asphaltene as a function of different mole fractions of injected gas is also imperative. In this study, the thermodynamic model of PC-SAFT EoS is used to discern the phase equilibrium of asphaltene by analyzing the asphaltene drop-out curve during gas injection. Asphaltene drop-out curves of two different live oil samples are analyzed by injecting CO2, CH4, and N2 gases at different mole percentages and temperatures. The results revealed that PC-SAFT EoS can serve as a reliable tool for estimating bubble pressure and asphaltene onset pressure for a wide range of temperatures, pressures, and compositions. The simulation results for the injection of CO2, CH4, and N2 also showed that CO2 gas gives minimum asphaltene precipitation. It reduces the size of the drop-out curve or moves it toward higher pressures. CH4 and N2 expand the drop-out curve by raising the upper onset point. CH4 increases the maximum point of the drop-out curve for two types of oil studied (A and B) at two different temperatures. N2 raises the maximum point of oil type “A” by approximately 57% at 395 K, while it has no effect on the maximum point of oil type “B”. In addition, reducing the temperature resulted in either decrease or increase of asphaltene solubility, demonstrating that the impact of temperature on asphaltene precipitation is closely related to the composition of the crude.

Fluid Characterization for Miscible EOR Projects and CO2 Sequestration

2007 ◽  
Vol 10 (05) ◽  
pp. 482-488 ◽  
Author(s):  
Kristian Jessen ◽  
Erling Halfdan Stenby
Keyword(s):  
Phase Behavior ◽  
Oil Recovery ◽  
Reservoir Simulation ◽  
Co2 Sequestration ◽  
Gas Injection ◽  
Numerical Diffusion ◽  
Injection Process ◽  
Wide Range ◽  
Multicomponent Gas ◽  
The Impact

Summary Accurate performance prediction of miscible enhanced-oil-recovery (EOR) projects or CO2 sequestration in depleted oil and gas reservoirs relies in part on the ability of an equation-of-state (EOS) model to adequately represent the properties of a wide range of mixtures of the resident fluid and the injected fluid(s). The mixtures that form when gas displaces oil in a porous medium will, in many cases, differ significantly from compositions created in swelling tests and other standard pressure/volume/temperature (PVT) experiments. Multicontact experiments (e.g., slimtube displacements) are often used to condition an EOS model before application in performance evaluation of miscible displacements. However, no clear understanding exists of the impact on the resultant accuracy of the selected characterization procedure when the fluid description is subsequently included in reservoir simulation. In this paper, we present a detailed analysis of the quality of two different characterization procedures over a broad range of reservoir fluids (13 samples) for which experimental swelling-test and slimtube-displacement data are available. We explore the impact of including swelling-test and slimtube experiments in the data reduction and demonstrate that for some gas/oil systems, swelling tests do not contribute to a more accurate prediction of multicontact miscibility. Finally, we report on the impact that use of EOS models based on different characterization procedures can have on recovery predictions from dynamic 1D displacement calculations. Introduction During the past few decades, a significant effort has been invested in the studies and development of improved-oil-recovery processes. From a technical point of view, gas injection can be a very efficient method for improving the oil production, particularly in the case when miscibility develops during the displacement process. The lowest pressure at which a gas should be injected into the reservoir to obtain the multicontact miscible displacement—the minimum miscibility pressure (MMP)—has consequently attained a very important status in EOR studies. Various methods for measuring and calculating the MMP have been proposed in the literature. Many of these are based on simplifications such as the ternary representation of the compositional space. This method fails to honor the existence of a combined mechanism controlling the development of miscibility in real reservoir fluids. Zick (1986) and Stalkup (1987) described the existence of the condensing/vaporizing mechanism. They showed that the development of miscibility (MMP) in multicomponent gas-displacement processes could, independent of the mechanism controlling the development of miscibility, be predicted accurately by 1D compositional simulations. A semianalytical method for predicting the MMP was later presented by Wang and Orr (1997), who played an important role in the development and application of the analytical theory of gas-injection processes. Jessen et al. (1998) subsequently developed an efficient algorithm for performing these calculations, reducing the MMP calculation time to a few seconds even for fluid descriptions of 10 components or more. Later, Jessen et al. (2001) used this approach to generate approximate solutions to the dispersion-free, 1D-displacement problem for multicomponent gas-injection processes. Analytical and numerical methods for predicting the performance of a gas-injection process depend on an EOS to predict the phase behavior of the mixtures that form in the course of a displacement process. The role of the phase behavior in relation to numerical diffusion in compositional reservoir simulation has been pointed out previously by Stalkup (1990) and by Stalkup et al. (1990). Recently, Jessen et al. (2004) proposed a method to quantify the interplay of the phase behavior and numerical diffusion in a finite-difference simulation of a gas-injection process. By analyzing the phase behavior of the injection-gas/reservoir-fluid system, a measure of the impact, referred to as the dispersive distance, can be calculated. The dispersive distance is useful when designing and interpreting large-scale compositional reservoir simulations.

scholarly journals Curvature-Based Equation of State for Microemulsion-Phase Behavior

SPE Journal ◽  
2018 ◽  
Vol 24 (02) ◽  
pp. 647-659 ◽  
Author(s):  
V. A. Torrealba ◽  
R. T. Johns ◽  
H.. Hoteit
Keyword(s):  
Equation Of State ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Industrial Applications ◽  
Data Availability ◽  
Behavior Modeling ◽  
Average Curvature ◽  
Wide Range ◽  
Definition Of ◽  
Spheroidal Geometry

Summary An accurate description of the microemulsion-phase behavior is critical for many industrial applications, including surfactant flooding in enhanced oil recovery (EOR). Recent phase-behavior models have assumed constant-shaped micelles, typically spherical, using net-average curvature (NAC), which is not consistent with scattering and microscopy experiments that suggest changes in shapes of the continuous and discontinuous domains. On the basis of the strong evidence of varying micellar shape, principal micellar curves were used recently to model interfacial tensions (IFTs). Huh's scaling equation (Huh 1979) also was coupled to this IFT model to generate phase-behavior estimates, but without accounting for the micellar shape. In this paper, we present a novel microemulsion-phase-behavior equation of state (EoS) that accounts for changing micellar curvatures under the assumption of a general-prolate spheroidal geometry, instead of through Huh's equation. This new EoS improves phase-behavior-modeling capabilities and eliminates the use of NAC in favor of a more-physical definition of characteristic length. Our new EoS can be used to fit and predict microemulsion-phase behavior irrespective of IFT-data availability. For the cases considered, the new EoS agrees well with experimental data for scans in both salinity and composition. The model also predicts phase-behavior data for a wide range of temperature and pressure, and it is validated against dynamic scattering experiments to show the physical significance of the approach.

Surfactant Retention in Berea Sandstone- Effects of Phase Behavior and Temperature

1982 ◽  
Vol 22 (06) ◽  
pp. 962-970 ◽  
Author(s):  
J. Novosad
Keyword(s):  
Porous Media ◽  
Crude Oil ◽  
Phase Behavior ◽  
Oil Recovery ◽  
Liquid Interface ◽  
Divalent Ions ◽  
Surfactant Precipitation ◽  
Wide Range ◽  
Solid Liquid Interface ◽  
Solid Liquid

Novosad, J., SPE, Petroleum Recovery Inst. Abstract Experimental procedures designed to differentiate between surfactant retained in porous media because of adsorption and surfactant retained because Of unfavorable phase behavior are developed and tested with three types of surfactants. Several series of experiments with systematic changes in one variable such as surfactant/cosurfactant ratio, slug size, or temperature are performed, and overall surfactant retention then is interpreted in terms of adsorption and losses caused by unfavorable phase behavior. Introduction Adsorption of surfactants considered for enhanced oil recovery (EOR) applications has been studied extensively in the last few years since it has been shown that it is possible to develop surfactant systems that displace oil from porous media almost completely when used in large quantities. Effective oil recovery by surfactants is not a question of principle but rather a question of economics. Since surfactants are more expensive than crude oil, development of a practical EOR technology depends on how much surfactant can be sacrificed economically while recovering additional crude oil from a reservoir.It was recognized earlier that adsorption may be only one of a number of factors that contribute to total surfactant retention. Other mechanisms may include surfactant entrapment in an immobile oil phase surfactant precipitation by divalent ions, surfactant precipitation caused by a separation of the cosurfactant from the surfactant, and surfactant precipitation resulting from chromatographic separation of different surfactant specks. The principal objective of this work is to evaluate the experimental techniques that can be used for measuring surfactant adsorption and to study experimentally two mechanisms responsible for surfactant retention. Specifically, we try to differentiate between the adsorption of surfactants at the solid/liquid interface and the retention of the surfactants because of trapping in the immobile hydrocarbon phase that remains within the core following a surfactant flood. Measurement of Adsorption at the Solid/Liquid Interface Previous adsorption measurements of surfactants considered for EOR produced adsorption isotherms of unusual shapes and unexpected features. Primarily, an adsorption maximum was observed when total surfactant retention was plotted against the concentration of injected surfactant. Numerous explanations have been offered for these peaks, such as a formation of mixed micelles, the effects of structure-forming and structurebreaking cations, and the precipitation and consequent redissolution of divalent ions. It is difficult to assess which of these effects is responsible for the peaks in a particular situation and their relative importance. However, in view of the number of physicochemical processes taking place simultaneously and the large number of components present in most systems, it seems that we should not expect smooth monotonically increasing isotherms patterned after adsorption isothemes obtained with one pure component and a solvent. Also, it should be realized that most experimental procedures do not yield an amount of surfactant adsorbed but rather a measure of the surface excess.An adsorption isotherm, expressed in terms of the surface excess as a function of an equilibrium surfactant concentration, by definition must contain a maximum if the data are measured over a sufficiently wide range of concentrations. SPEJ P. 962^

Phase Behavior, Wettability Alteration, and Oil Recovery of Low-Salinity Surfactant Solutions in Carbonate Reservoirs

SPE Journal ◽  
2020 ◽  
Vol 25 (04) ◽  
pp. 1784-1802 ◽  
Author(s):  
Sepideh Veiskarami ◽  
Arezou Jafari ◽  
Aboozar Soleymanzadeh
Keyword(s):  
Phase Behavior ◽  
Oil Recovery ◽  
Wettability Alteration ◽  
Study Phase ◽  
Low Salinity ◽  
Angle Measurements ◽  
Contact Angle Measurements ◽  
Favorable State ◽  
Phase Behaviors ◽  
The Impact

Summary Recent investigations have shown that treatment with injected brine composition can improve oil production. Various mechanisms have been suggested to go through the phenomenon; nevertheless, wettability alteration is one of the most commonly proposed mechanisms in the literature. Wettability alteration of the porous media toward a more favorable state reduces the capillary pressure, consequently contributing to the oil detachment from pore walls. In this study, phase behavior, oil recovery, and wettability alteration toward a more favorable state were investigated using a combination of formulations of surfactant and modified low-salinity (LS) brine. Phase behaviors of these various formulations were examined experimentally through observations on relative phase volumes. Experiments were performed in various water/oil ratios (WORs) in the presence of two different oil samples, namely C1 and C2. These experiments were conducted to clarify the impact of each affecting parameter; in particular, the impact of resin and asphaltene of crude oil on the performance of LS surfactant (LSS) flooding. Hereafter, the optimal formulation was flooded into the oil-wet micromodel. Optimum formulations increased the capillary number more than four orders of magnitude higher than that under formation brine (FB) flooding, thus causing oil recovery rates of 61 and 67% for oil samples C1 and C2, respectively. Likewise, the wettability alteration potential of optimized formulations was studied through contact angle measurements. Results showed that LS and LSS solutions could act as possible wettability alternating methods for oil-wet carbonate rocks. Using the optimum formulation resulted in a wettability alteration index (WAI) of 0.66 for sample C1 and 0.49 for sample C2, while using LS brine itself ended in 0.51 and 0.29 for oil samples C1 and C2, respectively.

Theoretical and Numerical Investigation of Supersonic Multiphase Gas Injection

2021 ◽  
Author(s):  
Da Zhu ◽  
Mohan Sivagnanam ◽  
Ian Gates
Keyword(s):  
Shock Wave ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Single Phase ◽  
Gas Injection ◽  
Continuous Phase ◽  
Solid Particles ◽  
Gas Flows ◽  
Theoretical Derivation ◽  
The Impact

Abstract Supersonic gas injection can help deliver gas uniformly to a reservoir, regardless of reservoir conditions. This technology has played a key role in enhanced oil recovery (EOR) and in particular, thermal enhanced oil recovery operations. Most previous studies have focused on single phase gas injection whereas in most field applications, multiphase and multicomponent situations occur. In the research documented in this paper, we report on results of evaluations of compressible multiphase supersonic gas flows in which gas is the continuous phase is seeded with dispersed liquid droplets or solid particles. Theoretical derivation and numerical simulations with and without relative motions between continuous and disperse phases are examined first. The results illustrate that the shock wave structures and flow properties associated with the multiphase gas flows are different than that of single-phase isentropic flows. The existence and importance of relaxation zones after the normal shock wave in multiphase flow is described. Numerical computational fluid dynamics (CFD) simulations are conducted to show how the multiphase multicomponent flow affects gas phase injection under different conditions. The impact of solid/liquid mass loading on flow performance is discussed. Finally, the practical application of the findings is discussed.

Minimum Miscibility Pressure of CO2/Hydrocarbon Systems Within Nanopores

2021 ◽  
Author(s):  
Gang Yang ◽  
Xiaoli Li
Keyword(s):  
Oil Recovery ◽  
Gas Injection ◽  
Unconventional Reservoirs ◽  
Minimum Miscibility Pressure ◽  
Theoretical Approaches ◽  
Fluid Systems ◽  
Confined Fluid ◽  
Miscible Gas Injection ◽  
Fluid Characterization ◽  
The Impact

Abstract Minimum miscibility pressure (MMP), as a key parameter for the miscible gas injection enhanced oil recovery (EOR) in unconventional reservoirs, is affected by the dominance of nanoscale pores. The objective of this work is to investigate the impact of nanoscale confinement on MMP of CO2/hydrocarbon systems and to compare the accuracy of different theoretical approaches in calculating MMP of confined fluid systems. A modified PR EOS applicable for confined fluid characterization is applied to perform the EOS simulation of the vanishing interfacial tension (VIT) experiments. The MMP of multiple CO2/hydrocarbon systems at different pore sizes are obtained via the VIT simulations. Meanwhile, the multiple mixing cell (MMC) algorithm coupled with the same modified PR EOS is applied to compute the MMP for the same fluid systems. Comparison of these results to the experimental values recognize that the MMC approach has higher accuracy in determining the MMP of confined fluid systems. Moreover, nanoscale confinement results in the drastic suppression of MMP and the suppression rate increases with decreasing pore size. The drastic suppression of MMP is highly favorable for the miscible gas injection EOR in unconventional reservoirs.

Asphaltene Thermodynamic Flocculation during Immiscible Nitrogen Gas Injection

SPE Journal ◽  
2021 ◽  
pp. 1-17
Author(s):  
Mukhtar Elturki ◽  
Abdulmohsin Imqam
Keyword(s):  
Pore Size ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Filter Paper ◽  
Mixing Time ◽  
Injection Pressure ◽  
Weight Percent ◽  
Asphaltene Precipitation ◽  
Nitrogen Injection ◽  
The Impact

Summary Gas-enhanced oil recovery is one of the most advantageous enhanced oil recovery methods. Nitrogen is one of the most investigated gases because of its beneficial properties. However, during its interaction with crude oil, nitrogen can induce asphaltene deposition, which may result in severe formation damage and pore plugging. Few works have investigated the impact of nitrogen on asphaltene instability. This research studied the immiscibility conditions for nitrogen in nanopores and the impact of nitrogen on asphaltene precipitations, which could lead to plugging pores and oil recovery reduction. A slimtube was used to determine the minimum miscibility pressure (MMP) of nitrogen to ensure that all the experiments would be carried out below the MMP. Then, filtration experiments were conducted using nanofilter membranes to highlight the impact of the asphaltene particles on the pores of the membranes. A special filtration vessel was designed and used to accommodate the filter paper membranes. Various factors were investigated, including nitrogen injection pressure, temperature, nitrogen mixing time, and pore size heterogeneity. Supercritical phase nitrogen was used during all filtration experiments. Visualization tests were implemented to observe the asphaltene precipitation and deposition mechanism over time. Increasing the nitrogen injection pressure resulted in an increase in the asphaltene weight percent in all experiments. Decreasing the pore size of the filter membranes resulted in an increase in the asphaltene weight percent. Greater asphaltene weight percents were observed with a longer nitrogen mixing time. Visualization tests revealed that asphaltene clusters started to form after 1 hour and fully deposited after 12 hours in the bottom of the test tubes. Chromatography analysis of the produced oil confirmed that there was a reduction in the heavy components and asphaltene weight percent. Microscopy and scanning electron microscopy (SEM) imaging of the filter paper membranes found that significant pore plugging resulted from asphaltene deposition and precipitation. This research investigated asphaltene precipitation and deposition during immiscible nitrogen injection to understand the main factors that impact the success of using such a technique in unconventional shale reservoirs.

Impact of condition monitoring on reciprocating compressor efficiency

2018 ◽  
Vol 24 (4) ◽  
pp. 529-543 ◽  
Author(s):  
Jim Townsend ◽  
M. Affan Badar
Keyword(s):  
Condition Monitoring ◽  
Oil Recovery ◽  
Economic Benefits ◽  
Temperature Monitoring ◽  
Strong Impact ◽  
Pressure Monitoring ◽  
Monitoring Technology ◽  
Content Type ◽  
Wide Range ◽  
The Impact

Purpose Reciprocating compressors offer an efficient method of compressing almost any gas composition in a wide range of pressures and have numerous applications. Condition monitoring of critical rotating machinery is widely accepted by operators of centrifugal compressors. However, condition monitoring of reciprocating machinery has not received the same degree of acceptance. An earlier study (Townsend et al., 2016) was conducted on temperature monitoring. The purpose of this paper is to examine the impact of continuous pressure monitoring on electric-driven compressors. Design/methodology/approach This research analyzes the impact of continuous pressure monitoring on a fleet of 14 compressors transporting CO2 for enhanced oil recovery. The reliability and efficiency data on 14 reciprocating compressors over a three-year period were analyzed for failures detectable by the condition monitoring technology. The engineering economic analysis is presented to determine the impact this technology will have on the productivity of the compressors. Findings The study considers utilizing condition monitoring technology to analyze the pressure of the swept volume of the compressor cylinders. The results of the study indicate that continuous pressure monitoring technology has a strong impact on the productivity of the compressor fleet. The internal rate of return not only exceeds the operators hurdle rate, but the payback period is also dramatic. Pressure monitoring was found to be economically better than temperature monitoring. Originality/value The study reveals the economic benefits of implementing condition monitoring in the form of continuous pressure monitoring on reciprocating compressors.

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