Study of Resin Adsorption onto Asphaltene and Silica-Asphaltene Particles

Abstract

We present a methodology to study the adsorption behavior of resins on asphaltenes, which we call silica-asphaltene complex methodology (SACOM), and compare it to a methodology regularly used by many researchers (Acevedo et al., 1995 Acevedo, S., Ranaudo, M., Escobar, G., Gutiérrez, L. and Ortega, P. 1995. Adsorption of asphaltenes and resins on organic and inorganic substrates and their correlation with precipitation problems in production well tubing. Fuel., 74: 595–598. [Crossref], [Web of Science ®] , [Google Scholar]; González et al., 2003 González, G., Neves, G., Saraiva, S., Lucas, E. and Anjos de Sousa, M. 2003. Electrokinetic Characterization of Asphaltenes and the Asphaltenes-Resins Interaction. Energ. Fuel., 17: 879–886. [Crossref], [Web of Science ®] , [Google Scholar]; León et al., 2002 León, O., Contreras, E., Rogel, E., Dambakli, G., Acevedo, S., Carbornani, L. and Espidel, J. 2002. Adsorption of Native Resins on Asphaltene Particles: A Correlation between Adsorption and Activity. Langmuir, 18: 5106–5112. [Crossref], [Web of Science ®] , [Google Scholar]; Marczewski et al., 2002 Marczewski, A. and Szymula, M. 2002. Adsorption of asphaltenes from toluene on mineral surface. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 208: 259–266. [Crossref], [Web of Science ®] , [Google Scholar]; Pereira et al., 2007 Pereira, J. C., López, I., Salas, R., Silva, F., Fernández, C., Urbina, C. and López, J. C. 2007. Resins: The Molecules Responsible for the Stability/Instability Phenomena of Asphaltenes. Energ. Fuel., 21: 1317–1321.  [Google Scholar]) that we call traditional methodology. Three isotherms of resins adsorbed on the complex substrates (asphaltene and its colloidal fractions A₁ and A₂ adsorbed on silica) were built, analyzed, and then compared with two isotherms built by applying a traditional methodology where resins were adsorbed on two organic substrates: asphaltene and its fraction A₁.     

Treatment and restoration of used mineral-oil-based hydraulic fluids from different machines. Part 2: Effect of additives on oil properties restoration

This work is an extension of our previous work, (Ahmed et al. 2018 Ahmed S. Eissa, Nagat I. Mohammed, Renee I. Abd-Allah &; Shakinaz T. El-Sheltawy. 2018. Treatment and restoration of used Mineral-Oil-Based hydraulic fluids from different machines. Part 1: Dewatering, filtration and effect of viscosity modifier. Petroleum Science and Technology. 36 (9–10):666–674. doi:10.1080/10916466.2018.1442854.[Taylor &; Francis Online] , [Google Scholar]). In this work, we investigate the effect of additives on restoration of properties of used mineral-based hydraulic oils. The additives were added to improve water separation, pour point, oxidation stability, thermal stability and anti-foaming properties. The effect of additives concentration was assessed, exhibiting optimum concentrations that yield maximum recovery of oil properties. The results show that the treated oil samples passed the tests of water separability and foaming tendency (seq. I and III). However, the other properties; such as oxidation stability, thermal stability, and foaming tendency (seq. Π) were improved but still fail to reach the allowable limits.     

Selection methodology for screening evaluation of EOR methods

The choice of enhanced oil recovery (EOR) methods for specific reservoir conditions is one of the most difficult tasks for a reservoir engineer. Taber (Taber, 1980 Taber, J. J. (1980). Research on enhanced oil recovery: past, present and future. Pure Appl. Chem., 52:1323–1347.[Crossref], [Web of Science ®] , [Google Scholar]; Taber et al., 1997a,b Taber, J. J., Martin, F. D., and Seright, R. S. (1997a). EOR screening criteria revisited. Part 1: Introduction to screening criteria and enhanced recovery field projects. SPE-35385-PA. Taber, J. J., Martin, F. D., and Seright, R. S. (1997b). EOR screening criteria revisited. Part 2: Applications and impact of oil prices. SPE-39234-PA. ) gave informative overview of EOR research history. He also offered technical screening guides for EOR nowadays known as Taber's tables. It should be noted that the approach recommended by Taber could not be taken as strong mathematical ranking of EOR methods. The authors propose an approach for EOR methods selection, based on fuzzy logic, possibility theory, and Bayesian inference mechanisms. Rankings were made by way of best EOR method selection for every criteria using fuzzy intervals comparison. Final correction of each EOR selection coefficient was performed by the generalized Bayesian inference mechanism. Application of this methodology for reservoir conditions of Alberta oil field, as well as the offshore field “Guneshli,” allowed for choosing the most effective EOR method, confirming the accuracy and feasibility of the proposed approach. Simple calculation (not more than five iterations) allows the automation of the process of selecting the most effective EOR method for a particular field.     

Formation Pore Pressure Prediction Using Velocity Inversion in Southwest Iran

Abstract

Surface seismic data include necessary information for predicting the formation of pore pressure in hydrocarbon reservoirs. In this article, formation pore pressure was predicted based on the velocity inversion method for a gas reservoir located in the southwest of Iran. Firstly, for this purpose, seismic data were inverted to obtain velocity values. Secondly, these values were converted to effective stress by using Bowers' equation (1994). In addition, the overburden stress was estimated from the Amoco equation (Huffman et al., 2011 Huffman, A. R., Meyer, J., Gruenwald, R., Buitrago, J., Suarez, J., Diaz, C., Munoz, J. M. and Dessay, J. 2011. Recent advances in pore pressure prediction in complex geologic environments Manama, , Bahrain March 20–23, SPE Paper No. 142211-PP [Google Scholar]). To obtain formation pore pressure, the effective stress was subtracted from the estimated overburden stress. The results showed a normal distribution of formation pore pressure versus depth.     

Estimation of the CO2-oil minimum miscibility pressure for enhanced oil recovery

The authors' aim was to present new models based on artificial neural network (ANN) and two optimization algorithms including cuckoo optimization algorithm (COA) and teaching learning based optimization (TLBO) to predict the pure and impure CO₂ MMP. Thirty-four and 11 training and testing data sets were used to develop these models with following inputs: reservoir temperature, the mole percent of volatile oil components (C₁ and N₂), mole percent of intermediate oil components (C₂-C₄, CO₂, and H₂S), molecular weight of C₅₊ fraction in oil phase (MW_C5+) and mole percentage of CO₂, N₂, C₁, C₄, and H₂S in the injected gas. Statistical comparisons show that although two models yield acceptable results, the ANN-TLBO model has better performance with the lower mean absolute percentage error (2.6%) and standard deviation (3.37%) and the higher coefficient of determination (0.993). Moreover, among the available correlations, the Cronquist's (1978 Cronquist, C. (1978). Carbon dioxide dynamic miscibility with light reservoir oils. Fourth Annual U.S. DOE Symposium, Tulsa, Oklahoma. [Google Scholar]; corrected by Sebastian et al., 1985 Sebastian, H. M., Wenger, R. S., and Renner, T. A. (1985). Correlation of minimum miscibility pressure for impure CO2 streams. J. Pet. Technol. 37:2076–2082.[Crossref] , [Google Scholar]) correlations have better performance. Finally, the sensitivity analysis on the ANN-TLBO showed that MW_C5+ and reservoir temperature are the most influential parameters in determining the CO₂ MMP, respectively.     

Asphaltene Precipitation Prediction Using a Micellization Model Based on Experimental Data

Abstract

Thermodynamic modeling is a promising tool for prediction of asphaltene precipitation. However, most thermodynamic models do not consider the micellar nature of petroleum fluids and the interaction between asphaltene-resin molecules. In addition, the accuracy of the predictions from the Peng-Robinson equation of state (PR-EOS) depends on the mixing rule. In this work, a thermodynamic framework based on the micellization model is used to describe the structure of asphaltene micelles as well as asphaltene precipitation in crude oil and the Wong and Sandler (1992) Wong, D. S. H. and Sandler, S. I. 1992. A theoretically correct mixing rule for cubic equations of state. AIChE J., 38: 671–680. [Crossref], [Web of Science ®] , [Google Scholar] mixing rule also is applied. The results show that the model predictions are matched well with the generated data for two Iranian crude oils.     

Natural gas hydrate dissociation by hot brine injection

Hot brine injection is one of the most effective dissociation methods of natural gas hydrate, and the movement of thermal front is a key parameter to evaluate the production performance by hot brine injection. Based on the principle of energy conservation, a mathematical model for thermal front movement of gas hydrate dissociation by hot brine injection is developed, which is derived through Laplace transform. In addition, an experimental study on the movement of thermal front is conducted with a self-designed 1D natural gas hydrate dissociation apparatus. The thermal front movement of the experiment is compared with that calculated from the mathematical model established in this paper as well as other two models proposed by Selim and Sloan (1990 Selim, M. S., and Sloan, E. D. (1990). Hydrate dissociation in sediment. SPE 16859. [Google Scholar]) and Tang et al. (2006 Tang, L., Li, G., Feng, Z., et al. (2006). Mathematical simulation of gas hydrate dissociation by heating injection. Nat. Gas Industry 26:105–107. [Google Scholar]), respectively. It turns out that what fits better with the experimental data is the energy conservation model, which includes the effect of heat used to warm the dissociated reservoir, heat absorption by hydrate dissociation and heat loss to the cap and base sediments. Therefore, this energy conservation model is an effective method to analyze the thermal front of gas hydrate dissociation by hot brine injection.     

Obtaining of Ashless Additives for Diesel Fuel Impoving the Lubricating,Anticorrosion and Protection Properties

Abstract

The production of “ultra pure” diesel fuels is connected with the deterioration of their certain performance characteristics. The lubricating properties of ultra pure diesel fuels are poor; their relative stability worsens; they tend to be corrosion-aggressive toward metal surfaces; and their electrophysical properties sharply deteriorate to increase the possibilities for accumulation of static-electric charge by transportation and feeding into vehicles (Tasheva, Petkov, and Ivanov, 2003 Tasheva, J., Petkov, P. and Ivanov, Sl. 2003. Contemporary trends in connection with the reduction of sulfur oxides at burning of fuels. Annual of University Prof. Dr. Assen Zlatarov, Bourgas, Bulgaria, XXXII(1): 150–155.  [Google Scholar]; 2004 Tasheva, J., Petkov, P. and Ivanov, Sl. 2004. Reduction of the contents of sulphur-containing organic compounds, arene hydrocarbons and resinous products in diesel fuels by applying extraction with selective solvents. Oxidation Communications, 27(1): 48–57.  [Google Scholar]).

These negative properties of the ultra pure diesel fuel are usually overcome by adding special substances to improve their lubricating properties, electric conductivity, and oxidation stability and to eliminate their corrosion aggressiveness.     

Technical and Economical Analysis of Hydrogen Sulfide Removal from the Recycled Hydrogen in a Diesel Hydrodesulfurization Plant

Abstract

Hydrodesulfurization (HDS) is a catalytic process used to remove sulfur compounds, which leads to very low sulfur concentrations. HDS turns more complicated and severe according to the feedstock boiling range, since sulfur compounds present in light cuts, normally sulfides and mercaptanes, are easy to remove, and sulfoaromatic compounds, specially polycyclics, are the more refractive ones (Speight, J. G. (1981 Speight, J. G. 1981. The Desulfurization of Heavy Oils and Residua Chemical Industries 4. , 2nd ed. Marcel Dekker Inc.  [Google Scholar]). The Desulfurization of Heavy Oils and Residua. 2nd ed. Marcel Dekker, Inc.: Chemical Industries 4.) The hydrogen sulfide (H₂S) produced in the HDS has an inhibiting effect on the same reaction, as it has been widely observed (McCulloch, D. C. (1983 McCulloch, D. C. 1983. Applied Ind. Catal., I: 69 [Google Scholar]). Applied Ind Catal. I:69; National Petroleum Refining Association (NPRA). (1993 National Petroleum Refining Association, NPRA. 1993. Questions & Answers 99 [Google Scholar]). Questions & Answers, 99; Leglise, J., Van Gestel, J., Duchet, J. C. (1994 Leglise, J., Van Gestel, J. and Duchet, J. C. Symposium on advances in hydrotreating catalysts presented before the division of petroleum chemistry Inc. 208th National Meeting. pp.pp. 533Washington, D.C.: American Chemical Society.  [Google Scholar]). Symposium on Advances in Hydrotreating Catalysts Presented before the Division of Petroleum Chemistry Inc. In: 208th National Meeting American Chemical Society. Washington D.C. p. 533). This effect is well known even at relatively low H₂S concentrations (2 mol%) for commercial operation conditions (Leglise, J., Van Gestel, J., Duchet, J. C. (1994 Leglise, J., Van Gestel, J. and Duchet, J. C. Symposium on advances in hydrotreating catalysts presented before the division of petroleum chemistry Inc. 208th National Meeting. pp.pp. 533Washington, D.C.: American Chemical Society.  [Google Scholar]). Symposium on Advances in Hydrotreating Catalysts Presented before the Division of Petroleum Chemistry Inc. In: 208th National Meeting American Chemical Society. Washington D.C. p. 533). Due to this, the H₂S removal from the recycled hydrogen to the reactor is mandatory in order to increase the desulfurization levels or to increase the processing capacity of an HDS plant. There are many options to low the H₂S concentration in the H₂ loop (Cooper, A., Stanislaus, A., Hannerup, P. N. (June 1993 Cooper, A., Stanislaus, A. and Hannerup, P. N. 1993. Hyd. Process., June: 84 June [Google Scholar]). Hyd Process 84; Johnson, A. D. (1983 Johnson, A. D. 1983. Oil and Gas J., 10: 78 [Google Scholar]). Oil and Gas J 10:78; Nash, R. M. (1989 Nash, R. M. 1989. Oil and Gas J., 13: 47 [Google Scholar]). Oil and Gas J 13:47; Suchanek, A. J., Dave, D., Gupta, A., Van Stralen, H., Karlsson, K. (1993 Suchanek, A. J., Dave, D., Gupta, A., Van Stralen, H. and Karlsson, K. NPRA Annual Meeting. AM-93-24 [Google Scholar]). In: NPRA Annual Meeting AM-93-24; Tippett, T., Knudsen, K. G. (1999 Tippett, T. and Knudsen, K. G. NPRA Annual Meeting. San Antonio, TX. AM-99-06 [Google Scholar]). In: NPRA Annual Meeting. San Antonio, TX. 1999 NPRA Annual Meeting, San Antonio, TX, AM-99-06.), which are from a simple purge adjustment for light naphtha HDS to a full treatment of the H₂ stream for middle distillate HDS, where the H₂S concentration can reach levels of 10 mol% (National Petroleum Refining Association (NPRA). (1993 National Petroleum Refining Association, NPRA. 1993. Questions & Answers 99 [Google Scholar]). Questions & Answers, 99). This work presents the economical analysis of the introduction of an Amine Treating Unit in an HDS plant in operation to remove H₂S from the H₂ stream recycled to the reactor.     

A New Modified Compositional Viscosity Model for Medium-heavy Oils

Viscosity of heavy oils is a key parameter in designing potential enhanced oil recovery methods. The recently proposed semiempirical viscosity model by Lindeloff et al. (2004) Lindeloff, N., Pedersen, K. S., Rønningsen, H. P. and Milter, J. 2004. The corresponding states viscosity model applied to heavy oil systems.. J. Can. Pet. Technol., 43: 47–53. [Web of Science ®] , [Google Scholar] was studied in depth. This model is the simplest yet powerful tool for medium-heavy oil viscosities. Based on the analysis, appropriate adjustments have been suggested, with the major one being the division of the pressure-viscosity profile into three different regions. New modifications have improved the overall fit, including the saturated viscosities at low pressures. The %AAD for the data sets studied was found to be 1.37. However, with the limited geographically diverse data, it is not possible to make a comprehensive predictive model. A few limitations of the new model are also stated.     

Effects of Memory on the Complex Rock-Fluid Properties of a Reservoir Stress-Strain Model

Abstract

The memory based stress-strain model developed earlier by Hossain et al. (2007) Hossain, M. E., Mousavizadegan, S. H., Ketata, C. and Islam, M. R. 2007. A novel memory based stress-strain model for reservoir characterization. Journal of Nature Science and Sustainable Technology, 1: 653–678.  [Google Scholar] has been solved numerically in this study. The derived mathematical model introduces the effects of temperature, surface tension, and pressure variations and the influence of fluid memory on the stress-strain relationship. The variation of shear stress as a function of strain rate is obtained for fluid in a sample oil reservoir to identify the effects of fluid memory. The stress-strain formulation related with the memory is taken into account, and we obtain the variation of it with time and distance for different values of α. The dependency of the stress-strain relation on fluid memory is considered to identify its influence on time. As pressure is also a function of space, the memory effects on stress and strain are shown in space with the pressure gradient change. The computation indicates that the effect of memory causes nonlinearity, leading to chaotic behavior of the stress-strain relationship. This model can be used in reservoir simulation and rheological study, well test analysis, and surfactant and foam selection for enhanced oil recovery.     

Prediction of Explosive Performance Properties of z-DBBD and Its Isomers by Quantum Chemical Computations

Theoretical studies have been performed on TACOT, its benzofuroxan derivative z-DBBD, and three different isomers of z-DBBD. The corrected absolute and relative total energies of the geometry-optimized structures were calculated at the theoretical level of B3LYP/6-31G(d,p). The bond dissociation energies were correlated with sensitivity. Mulliken electronegativities (χ_M) and chemical hardness (η) were obtained by employing frontier molecular orbitals at the HF/6-31G(d,p)//B3LYP/6-31G(d,p) theoretical level. Detonation performance analyses for z-DBBD (4,11-dinitro[1 Molchanova , M. S. , T. S. Pivina , E. A. Arnautova , and N. S. Zefirov . 1999 . Computer-aided search for high-density energetic compounds among hydrogen-free heterocycles . Journal of Molecular Structure (Theochem) , 465 : 11 – 24 .[Crossref], [Web of Science ®] , [Google Scholar],2 Kamlet , M. J. and S. F. Jacobs . 1968 . Chemistry of detonations. I. A simple method for calculating detonation properties of C H N O explosives . Journal of Chemical Physics , 48 : 23 – 25 .[Crossref], [Web of Science ®] , [Google Scholar],5 Kamlet , M. J. and H. J. Hurwitz . 1968 . Chemistry of detonations. IV. Evaluation of a simple predictional method for detonation velocities of C-H-N-O explosives . Journal of Chemical Physics , 48 : 3685 – 3692 .[Crossref], [Web of Science ®] , [Google Scholar]]-oxadiazolo[3,4-e][1 Molchanova , M. S. , T. S. Pivina , E. A. Arnautova , and N. S. Zefirov . 1999 . Computer-aided search for high-density energetic compounds among hydrogen-free heterocycles . Journal of Molecular Structure (Theochem) , 465 : 11 – 24 .[Crossref], [Web of Science ®] , [Google Scholar],2 Kamlet , M. J. and S. F. Jacobs . 1968 . Chemistry of detonations. I. A simple method for calculating detonation properties of C H N O explosives . Journal of Chemical Physics , 48 : 23 – 25 .[Crossref], [Web of Science ®] , [Google Scholar],5 Kamlet , M. J. and H. J. Hurwitz . 1968 . Chemistry of detonations. IV. Evaluation of a simple predictional method for detonation velocities of C-H-N-O explosives . Journal of Chemical Physics , 48 : 3685 – 3692 .[Crossref], [Web of Science ®] , [Google Scholar]]oxadiazolo[3′,4′:4,5]benzotriazolo-[2,1-a]benzotriazol-6-ium inner salt 1,8-dioxide), its presently considered isomers, and TACOT were performed. The results showed that the performance of all compounds (compounds 1–4) was as good as that of RDX. The power index results showed that z-DBBD and its isomers were better than TACOT, RDX, and HMX. Compounds 1–4 are all reasonable candidates for high-energy-density materials (HEDMs).     

Crystal State of 1,3,5-Triamino-2,4,6-Trinitrobenzene (TATB) Undergoing Thermal Cycling Process

The present report aims to discuss the crystal state variation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) suffering from thermal cycling process. In this study, in situ X-ray powder diffraction (XRD) was employed to determine thermal expansion and crystal fragmentation, primarily attributed to its crystal state variation. The results showed that the change of crystal volume mainly stemmed from the thermal expansion at the c axis of crystal lattice, and TATB crystal had the same thermal expansion coefficients at a and b axes. It was also demonstrated that crystal fragmentation occurred during this process, and more auto-repair happened in the [002 Giefers , H. , M. Pravica , W. Yang , and P. Liermann . 2008 . Radiation-induced decomposition of explosives under extreme conditions . Journal of Physics and Chemistry of Solids , 69 : 2208 – 2212 . [Google Scholar]] plane of TATB than other planes. These results will have an implication on the process of TATB-based materials.     

A Modified Approach to Predict Pore Pressure Using the D Exponent Method: An Example from an Oil Field,South of Iran

The methodology for pore pressure prediction known as D exponent is a function of an exponent of adjustment that was originally defined for the Gulf of Mexico (Jorden and Shirley, 1966 Jorden, J. R. and Shirley, O. J. 1966. Application of drilling performance data to overpressure detection. J. Pet. Technol., 18: 1387–1394.  [Google Scholar]; Eaton, 1972 Eaton, B. A. 1972. Graphical method predicts geopressures worldwide. World Oil, 7: 100–104.  [Google Scholar]). A limiting factor of this methodology is the definition of the Normal Compaction Trend, which needs to be interpreted from the data (Mouchet and Mitchell, 1989 Mouchet, J. P. and Mitchell, A. 1989. Abnormal pressure while drilling. Manuals techniques 2. Boussens, , France: Elf Aquitaine..  [Google Scholar]). In this study, the D exponent methodology was modified to make it applicable to the Gachsaran formation in an oil field of Ahvaz, Iran. The approach consisted of calculating the ratio between effective stress and the D exponent at each well, in order to find a robust NCT for the entire field, thus reducing subjectivity in the traditional D exponent methodology. Pore pressure determinations from Measured Direct Tests at one well confirm the predictive capability of the approach.     

Prediction of Surface Tension of Pure Hydrocarbons by An Artificial Neural Network System

Abstract

In this study, a multilayer perceptron neural network with a back-propagation (BP) learning method containing three layers has been developed for prediction of surface tension of pure hydrocarbons. This model was developed using 211 experimental data on surface tension in the literature. Statistical criteria of R² and root mean square error (RMSE) for this network were 0.9997 and 0.0615, respectively. The accuracy and validity of this model were compared with the experimental data and results obtained from the Pazuki-Nikookar (PN) equation of state (EOS; Pazuki et al., 2007; Nikookar et al., 2008 Nikookar, M., Omidkah, M. R. and Pazuki, G. R. 2008. Prediction of density and solubility parameter of heavy oils and SARA fractions using cubic equations of state. Petrol. Sci. Tech., 26: 1904–1912. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) as well as some semi-experimental correlations such as Pitzer (1995) Pitzer, K. S. 1995. Thermodynamics, , 3rd ed. New York: McGraw-Hill..  [Google Scholar], Sastri and Rao (1999) Sastri, S. R. S. and Rao, K. K. 1999. A new temperature–thermal conductivity relationship for predicting saturated liquid thermal conductivity. Chem. Eng. J., 74: 161–169. [Crossref], [Web of Science ®] , [Google Scholar], and Brock and Bird (1955) Brock, J. R. and Bird, R. B. 1955. Surface tension and the principle of corresponding states. AIChE J., 1: 174–177. [Crossref], [Web of Science ®] , [Google Scholar]. Also, considering the results obtained by the artificial neural network system, a correlation is presented for estimation of the parachor constant and the results are compared with those obtained from equations of state.     

The Application of a New Association Equation of State (AEOS) for Prediction of Asphaltenes and Resins Deposition During CO2 Gas Injection

Abstract

Asphaltene deposition is a serious problem that can cause fouling in the reservoir, well, pipeline, and the oil production and processing facilities. An association equation of state (AEOS) is one of the most useful models used to predict asphaltene phase behavior and asphaltene deposition conditions. For an AEOS, it is assumed that the total compressibility factor consists of physical and chemical parts. The authors apply the conventional form of compressibility factor developed by G. Soave (1972) Soave, G. 1972. Equilibrium constants from a modified Redlich-Kwong equation of state. Chem. Eng. Sci., 27: 1197–1203. [Crossref], [Web of Science ®] , [Google Scholar] to the physical compressibility factor. However, for the chemical compressibility factor a new form is proposed. The total compressibility factor obtained is then used to calculate the asphaltene and resin deposits. The amounts of deposited asphaltenes calculated through the proposed model along with the experimental results are used to calculate resin deposit. A comparison with the experimental results shows that the new proposed model can be used to predict the amounts of deposited resins and asphaltenes within an acceptable range of accuracy.     

REV Grid Technique for Reservoir Upscaling

Abstract

Lasseter et al. (Lasseter, T. J., Waggoner, J. R., Lake, L. W. (1986 Lasseter, T. J., Waggoner, J. R. and Lake, L. W. 1986. Reservoir Heterogeneities and Their Influence on Ultimate Recovery. Reservoir Characterization 545Orlando, FL: Academic Press Inc..  [Google Scholar]). Reservoir Heterogeneities and Their Influence on Ultimate Recovery. Reservior Characterization, Orlando, Florida: Academic Press Inc., 545.) proposed that scale-up of properties should be done from the scale of a representative elementary volume (REV), a volume for which the measured property does not change with an increase in scale over a given limit of scale. The notion of REV has been a quite argued concept owing to its definition is not unequivocal, and it did not address how to obtain it in real system, some people even argue if REV really exists. Qi et al. (Qi, D., Wong, P. M., Liu, K. (2001 Qi, D., Wong, P. M. and Liu, K. 2001. An improved global upscaling approach for reservoir simulation. Petroleum Science and Technology, 19(7–8): 779–795. [CROSSREF][Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). An improved global upscaling approach for reservoir simulation. Petroleum Science and Technology 19(7–8):779–795.) based on REV concept, proposed the new idea of REVG (representative elemental volume grid). This article further developed this idea, and based on it, proposed the REV grid upscaling technique. This new technique uses an algorithm, which is a combination of two-procedure-upgridding with reverse stepwise approach, it is a field-oriented 3D model. The new method concentrates on constructing a unique coarse grid, referred to as pseudo-REVG, which could best describe the heterogeneity of the original model at given scale. Mathematically, the variance of properties in REVG is the smallest within each block, and largest between the blocks. The proposed method is applied to two case studies, one of them is a 3D multiphase real reservoir, and the flow simulation results show that the consistency of the reservoir behavior before and after upscaling with REV grid technique is excellent. It is much better than that of the conventional upscaling methods.     

Correlations Between the Pour Point/Gel Point and the Amount of Precipitated Wax for Waxy Crudes

Abstract:

The amount of precipitated wax is one of the key factors that governs the flow properties of waxy crudes. Experimental results of 24 crudes have shown that approximately 2 wt% precipitated wax is sufficient to cause a virgin waxy crude gelling. Accordingly, a correlation between the pour point and the temperature at which 2 wt% of wax has precipitated out from a crude oil; i.e., T _c (2 wt%), and a correlation between the gel point and T _c (2 wt%) have been developed. The proposed correlation of the pour point is in accordance with the correlation developed by Letoffe et al. (1995) Letoffe, J. M., Claudy, P., Kok, M. V., Garcin, M. and Vollet, J. L. 1995. Fuel, 74(6): 810–817. [CSA][CROSSREF][Crossref] , [Google Scholar] on the basis of 14 crudes from eight countries. The development of the gel point correlation and further verification of the pour point correlation indicate that there is a relationship between the gelling of virgin waxy crudes and the amount of precipitated wax. According to these correlations and the amount of precipitated wax, which can be determined only with a little sample by thermodynamic models or Differential Scanning Calorimetry (DSC) experiment, the gel point and pour point of virgin waxy crude can be predicted even if the oil sample is very limited. Heat treatment and chemical treatment can greatly improve flow behavior of waxy crudes, and more precipitated wax is present when the beneficiated (thermally beneficiated or PPD-beneficiated) crude oils gel. Experimental results showed that approximately two or three times the amount of precipitated wax presents at the gelling temperature when the oils were in their beneficiated (thermally beneficiated or PPD-beneficiated) conditions.     

Major Challenges for Reservoir Upscaling

Abstract

In the past two decades, many upscaling procedures have been proposed. The major methods are power-law average, renormalization technique, pressure-solver method, tenser method, and pseudo-function technique. The common problem of conventional upscaling methods is that they tend to smear out the spatially continuous extremes, such as shale barriers and open fractures. However, experience and previous simulation work in heterogeneous reservoirs have shown that oil recovery (especially water breakthrough oil recovery) mainly depends on the spatial connectivity of the extreme permeability values.

Lasseter et al. (1986) Lasseter, T. J., Waggoner, J. R. and Lake, L. W. 1986. “Reservoir heterogeneities and their influence on ultimate recovery.”. In Reservoir characterization Edited by: Schatzinger, R. A. and Jordan, J. F. 545Orlando: Academic Press, Inc..  [Google Scholar] proposed that scale-up of properties should be done from the scale of a representative elementary volume (REV), a volume for which the measured property does not change with an increase in scale over a given limit of scale. The notion of REV is physical-model oriented and proposed a criterion for upscaling technique. However, the decisive factor in upscaling is the grid system rather than individual physical point.

This article concludes that how to obtain REV for real system, how to evaluate the upscaling results quantitatively, how to treat extremes of permeability, as well as how to perform upscaling for naturally fractured reservoirs and carbonate reservoirs are the remained major challenging problems in this area. It is concluded that a great effort should be made on how to obtain the REV grid, which could best describe the heterogeneity of given reservoir at a given scale. Secondly how to perform the upscaling of all properties based on the REV grid is also a critical aspect and should be considered according to the different extent and pattern of heterogeneity of the original geological model respectively.     

Kinetic Modeling of Hydrodesulphurization of Residual Oils. II. Hyperbolic Models

Abstract

Fourteen models of the Hougen–Watson type were developed and tested for hydrodesulphurization (HDS) of benzothiophene and thiophene, which form the major part of sulphur usually present in residual oils. Model discrimination based on the positiveness of the rate and equilibrium constants, revealed that four of the models satisfied the set criteria. One of these models corresponds to that proposed by Kilanowski and Gates ([1980] Kilanowski and Gates, B. C. 1980. Kinetics of Hydrodesulphurization of Benzothiophene catalysed by sulphide Co-Mo/AI203. Journal Catalysis, 62: 70–78.  [Google Scholar]) for benzothiophene and the one derived by Satterfield and Roberts ([1968] Satterfield, C. N. and Roberts, G. W. 1968. Kinetics of hiphene Hydrogenolysis on Cobalt Molybdate Catalyst. A. I. Ch. E. Journal, 14: 159[Crossref], [Web of Science ®] , [Google Scholar]) for thiophene. A new model, which was determined by variance function analysis, suggests that the HDS of both benzothiophene and thiophene assumes a dual site mechanism and is first order in sulphur compound and second order in hydrogen.