Predict Yields from a Kinetic Model of Catalytic Cracking Process at Any Temperature

It has been observed that yields of gasoline and other petroleum fraction in a catalytic cracking process depends significantly upon the reaction temperature besides on other operating conditions. In this work, first the model was developed with the help of literature data with out considering the temperature effect. The important optimum parameters like relative rate constant (K₁), rate of coke deactivation or decay constants (K_d), order of reaction (m) etc. over suitable catalysts of cracking process were obtained using suitable numerical analysis techniques. On comparing the error based on the least square criteria, it has been noticed that the results from the first model show about 4% improvement in predicted error against literature results on cracking of normal Heptane [Corma, A., Wojciechowsky, B. W. ([1983]). Recent work on the fundamentals of catalytic cracking. American Chemical Society Reprints, Div. Chem. 28(3):861-874.] for fifteen data points. In the second step the software was modified to simulate the effect of reaction temperature by using two sets of laboratory data for the reaction of normal Hexadecane over ReY-Zeolite, a commercial cracking catalysts at two different reaction temperatures of 400 and 450°C respectively. Validation of modified software has been checked with the above system at 500°C and found that the predictions are quite close to experimental values. Such analytical model will be useful for finding optimum operating conditions to achieve maximum yields of potential products on cracking of a given feed without resource to conducting large number of experiments.     

Status of Dual-Continuum Models for Naturally Fractured Reservoir Simulation

Abstract

Naturally fractured reservoirs (NFR) contain significant portions of the world's proven reserves of conventional oil. However, their simulation is one of the most challenging and computationally intensive problems in reservoir engineering. Most commercial reservoir simulators use dual-continuum models to predict performance of an NFR where two overlapping continua for the fracture and matrix medium are considered. Then transfer of multiphase fluid between the two media is taken into consideration by a source-sink transfer function (Zhang and Sun, 2000 Zhang, D. and Sun, A. Y. 2000. Stochastic analysis of transient saturated flow through heterogeneous fractured porous media: A double-permeability approach. Water Resour. Res., 36: 865–874. [Crossref], [Web of Science ®] , [Google Scholar]). After review of different conceptual models to simulate an NFR, major pitfalls related to dual-porosity and dual-permeability models for simulation of such reservoirs will be discussed briefly within this article.     

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.     

The Kinetics of Hydrodesulphurization of Diesel: Pore Diffusion Aspects

Abstract

Indian fuel policy aims at producing ultra-low-sulfur diesel (ULSD) in the near future. A catalyst for meeting such requirements has been developed and the kinetics of this catalytic ultra-deep hydrodesulfurization (UDHDS) process is being looked into. Experiments were carried out in a flow microreactor over a presulfided catalyst and intrinsic parameters were estimated (Ganguly, 2009 Ganguly, S. K. Kinetics of hydrodesulphurization of diesel: Mass transfer aspects. International Conference on Energy and Environment, Enviroenergy 2009. March18–19, Chandigarh, India. pp.258–262.  [Google Scholar], 2010 Ganguly, S. K. Kinetics of hydrodesulphurization of diesel: Pore diffusion effects. International Symposium on Fuels and Lubricants, ISFL2010. March9–12, New Delhi, India.  [Google Scholar]). It was established that the UDHDS process is internal resistance controlled. In the present study we have tried to demonstrate by simulations how we could reduce the internal resistance by increasing the effective pore diffusivity so that the conversion of sulfur can be improved.     

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.     

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.     

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.     

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 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).     

A Four Lump Kinetic Model for the Simulation of the Hydrocracking Process

Abstract:

Hydrocracking is a very important secondary refining process used to convert low value vacuum gas oils into high value fuels. The chemistry of the hydrocracking process is very complex due to the involvement of high molecular weight complex hydrocarbons in the reactions. Process modeling and simulation of the hydrocracking unit is very challenging due to the complexities of chemistry and the process. In the present work, a mathematical model is described to analyze the performance of the hydrocracking process in terms of product yields. A four lump discrete lumping approach is employed with a hydrocracking reaction scheme involving six reactions. The kinetic constants for the reactions were estimated by minimizing the error between the experimental and predicted yields of kinetic lumps. Experimental data reported by Ali et al. (2002) Ali, M. A., Tatsumi, T. and Masuda, T. 2002. Development of heavy oil hydrocracking catalysts using amorphous silica-alumina and zeolites as catalyst supports. Applied Catalysis A: General, 233: 77–90. [CSA][Crossref], [Web of Science ®] , [Google Scholar] were used to validate the proposed model. The model predictions were found to agree well with the experimental data. The proposed model can be used to simulate the performance of commercial hydrocrackers using kinetic parameters estimated from pilot plant experiments.     

In situ combustion methods: Applicability to heavy oil reservoirs in the Niger Delta

Oil productions from conventional reservoirs are rapidly declining worldwide. Hence, there is a serious need for the Nigerian government to start looking at viable thermal EOR methods such as in situ combustion (ISC) as a means of enhancing possible heavy oil production in its Niger Delta region. This study looked at the applicability of ISC using the Nelson and McNeil model by subjecting the model's equations, assumptions, and correlations (as outlined in the ISC Handbook; Partha, 1999 Partha, S. S. (1999). In-situ combustion handbook - principles and practices. Tulsa, OK: BDM Petroleum Technologies. [Google Scholar]) to a foreign scenario (Case 1) and a Nigerian scenario (Case 2) to evaluate and compare performances.     

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.     

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.     

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.     

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.     

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.     

Viscosity Model for CO-Noble Gas Mixtures at Atmospheric Conditions

Abstract

We have presented an empirical model for predicting the viscosity of binary mixtures of gases, based on our previous correlation for natural gas mixtures (Miadonye and Clyburn, 2003 Miadonye, A. and Clyburn, W. 2003. Modelling the Viscosity of Natural Gas Mixtures, Computational Methods and Experimental Measurements, Edited by: Esteve. Southhampton, , UK: WIT Press.  [Google Scholar]). New parameters were derived for binary mixtures of carbon monoxide-noble gases and for carbon monoxide-nitrogen gases, for temperatures from 0–1000°C. The model was validated with the Chapman-Enskog equation for gas mixtures, with and without length scaling factor. For five equimolar and eight non-equimolar mixtures of gases at temperatures from 0–1000°C, the model gave an excellent viscosity prediction with an overall average absolute deviation of 0.45%. The model is simple to incorporate in design and simulation packages, and more accurate than any correlation currently used for estimating the viscosities of gas mixtures.     

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.     

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.