Showing papers in "Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles in 2008"

Enhanced Oil Recovery - An Overview

Abstract: Nearly 2.0 × 1012 barrels (0.3 × 1012 m3 ) of conventional oil and 5.0 × 1012 barrels (0.8 × 1012 m3 ) of heavy oil will remain in reservoirs worldwide after conventional recovery methods have been exhausted. Much of this oil would be recovered by Enhanced Oil Recovery (EOR) methods, which are part of the general scheme of Improved Oil Recovery (IOR). The choice of the method and the expected recovery depends on many considerations, economic as well as technological. This paper examines the EOR methods that have been tested in the field. Some of these have been commercially successful, while others are largely of academic interest. The reasons for the same are discussed. The paper examines thermal and non-thermal oil recovery methods. These are presented in a balanced fashion, with regard to commercial success in the field. Only a few recovery methods have been commercially successful, such as steam injection based processes in heavy oils and tar sands (if the reservoir offers favourable conditions for such applications) and miscible carbon dioxide for light oil reservoirs. Other recovery methods have been tested, and even produced incremental oil, but they have inherent limitations. The current EOR technologies are presented in a proper perspective, pointing out the technical reasons for the lack of success. Methods for improving oil recovery, in particular those concerned with lowering the interstitial oil saturation, have received a great deal of attention both in the laboratory and in the field. From the vast amount of literature on the subject, one gets the impression that it is relatively simple to increase oil recovery beyond secondary (assuming that the reservoir lends itself to primary and secondary recovery). It is shown that this is not the case. Many reservoirs suitable for steam injection and carbon dioxide have already been exploited and are approaching maturity. Other EOR methods suffer from limitations that have little to do with economics. Recovering incremental oil is complex and costly, and has been successful only for a few processes under exacting conditions. Nevertheless, EOR will continue to have an important place in oil production, in view of the escalating energy demand and the tight supply. It is suggested that much research is needed to develop technologies for recovering over two-thirds of the oil that will remain unrecovered in reservoirs. Key references are indicated.

Challenges of Modeling Steam Cracking of Heavy Feedstocks

Abstract: Today single event microkinetic (SEMK) models for steam cracking of hydrocarbons allow simulating the conversion of heavy fractions. The key challenge to model the cracking behavior of these heavy feedstocks is related to feedstock reconstruction. The latter depends on the required level of molecular detail of the reaction network and of the feedstock characterization/ reconstruction model. This is illustrated for gas condensate feedstocks. Comparison of yield predictions with yields obtained in a pilot plant illustrate how uncertainties in the feedstock characterization propagate to the simulation results. The combination of a SEMK model and the feedstock reconstruction method based on maximization of the Shannon entropy allows to obtain accurate simulation results, provided that the specific density, the global PIONA weight or volume fractions, and the initial, 50% and final boiling point are known. Specifying less commercial indices results in a decrease of the agreement between simulated and experimentally obtained product yields. The developed methodology can be extended in a straight forward way to any heavy feedstock.

The Colloidal Approach. A Promising Route for Asphaltene Deposition Modelling

Abstract: It is now widely recognized that asphaltene exist in crude oils both as dissolved and particulate matter and that asphatenic crude oils behave as colloidal systems. The objective of this research work is to check if, in porous media and under dynamic conditions, asphaltene also behave as colloids. In this case, their deposition kinetic should obey the classical laws for colloid deposition in porous media. To achieve this, asphaltene deposition kinetics has been investigated as a function of the main controlling parameters such as flow rate, asphaltene aggregation state, resin content and crude origin. The study has been performed, first under well controlled condition using model fluids and porous media, and then under more representative conditions using actual crude oils and outcrop sandstones. The results confirmed that, indeed, the kinetics of asphaltene deposition in porous media obeys the general scaling low of colloid deposition. They allowed us to propose general scaling laws for the deposition kinetics in the form , η is the capture efficiency and γ the shear rate. The exponents s are universal exponents that are characteristic of the deposition regimes while the power law pre-factors A encompass all the specific features of the system considered (asphaltene and porous media). These kinetic laws show that the thickness of the deposit increases rapidly with decreasing shear rate. Accordingly and under favourable conditions, a thick deposit is expected to form during heavy oil extraction from high permeability formations and under low flow rate conditions. Such deposition could then have significant impact on the efficiency of heavy oil recovery. Therefore, its impact on permeability and on flow properties of reservoir fluids needs to be assessed as a part of process optimisation and evaluation. The Colloidal approach provides a new and promising route for asphaltene deposition and associated permeability damage modelling.

Effect of the Temperature Variation on Properties of Biodiesel and Biodiesel-Ethanol Blends Fuels

Abstract: The purpose of this study is to investigate the effect of the temperature variation and blending ratios on fuel properties of biodiesel and biodiesel blended with ethanol fuel. Adding the ethanol to biodiesel fuel can be improved the disadvantage of cold-starting of biodiesel fuel. Furthermore, properties which depend on the change of fuel temperature affect the spray behavior, combustion and emission characteristics in combustion chamber. The kinematic viscosity and density were obtained by the measured dynamic viscosity and specific gravity, respectively. In this study, it was revealed that the specific gravity and density decreased linearly when the fuel temperature and the ethanol blending ratio increased. Empirical equation can be derived from the measured values and it is the function of the second order of blending ratio and the first order of fuel temperature. On the other side, the dynamic and kinematic viscosity decreased exponentially as rising of the fuel temperature. Based on the measured value of viscosities, the empirical equation which is the function of fuel temperature can be derived at each ethanol blending fuels.

Improved Oil Recovery of High-Viscosity Oil Pools with Physicochemical Methods and Thermal-Steam Treatments

Abstract: Novel physicochemical technologies have been developed at IPC SB RAS to improve oil recovery from high-viscosity oil pools using thermal-steam and cyclic-steam treatments. The results of laboratory investigations and pilot tests carried out in oil fields of Russia and China are presented. The use of thermotropic inorganic and polymer gels increases coverage by steam injection, decreases water cut of the production well by 3-45%, increases the oil production rate by 11-33% and decreases the fluid production rate by 14-25%. Surfactant-based systems, generating CO2 and alkaline buffer solution in situ, decrease oil viscosity 2-3 times and water cut of the production well by 10-20% and thereby increase the oil production rate by 40% and the fluid production rate by 5-10%.

Solvation Phenomena in Association Theories with Applications to Oil & Gas and Chemical Industries

Abstract: Association theories e.g. those belonging to the SAFT family account explicitly for self- and cross-association (solvation) phenomena. Such phenomena are of great practical importance as they affect, often dramatically, the phase behaviour of many mixtures of industrial relevance. From the scientific point of view, solvation phenomena are also very significant because they are present in different types of mixtures and not just those containing two self-associating compounds e.g. water with alcohols or glycols. Mixtures with only one self-associating compound and in some cases even mixtures with two non self-associating compounds may exhibit solvation specifically due to hydrogen bonding or more generally due to Lewis acid-Lewis base interactions. As examples can be mentioned mixtures with polar compounds (water, glycols...) and aromatic hydrocarbons and aqueous ether or ester solutions. This manuscript presents how a specific association thermodynamic model, which employs SAFT's association term, the so-called CPA (Cubic-Plus-Association) equation of state, can be applied in order to account for various types of interactions due to solvation. The role of combining rules in the association term and the cases where explicit treatment of solvation is needed will be illustrated.

Asphaltenes Size Polydispersity Reduction by Nano- and Ultrafiltration Separation Methods – Comparison with the Flocculation Method

Abstract: Asphaltenes consist of a very complex material in which molecules and aggregates can have very different chemical composition and molecular weights. It is now well documented that asphaltenes show a very large size polydispersity. All these differences make their properties and behavior hard to describe. In order to gain insight into asphaltene properties, it could be useful to reduce this size polydispersity. Within this framework, two different approaches were used to reduce asphaltene size polydispersity: flocculation (using mixtures of solvents with anti-solvents) and membrane filtration. Various asphaltene fractions were obtained by both methods, and were further investigated using the following techniques: Size-Exclusion Chromatography (SEC), Elemental analysis, Nuclear Magnetic Resonance (13 C-NMR) and Small-Angle X-ray Scattering (SAXS). It has been shown that asphaltenic aggregates of different sizes can be fractionated by membrane filtration in a more selective way than using the conventional solvent flocculation method. The effects of temperature and concentration on membrane separation performance were studied. When compared with large aggregates, small asphaltenic aggregates present lower aromaticity and higher aliphatic composition. Their alkyl chains also appear to be shorter and more alkylated. Elemental analysis indicates that smaller asphaltenes contain a lower metal concentration and are preferentially enriched in vanadium than nickel when compared with bigger aggregates.

Destabilisation of Water-in-Crude Oil Emulsions by Silicone Copolymer Demulsifiers

Abstract: Asphaltene aggregates are known to form viscoelastic film preventing the coalescence of droplets in water-in-oil emulsions formed during crude oil exploitation. Since phase separation is necessary for oil refining process, demulsifying additives are used. It was found that formulations based on polysiloxane copolymers promote separation of water from crude oil even at very low concentration (few tens of ppm). Two alternative scenarios of emulsion destabilisation can be envisaged: (i) dissolution of asphaltene aggregates or (ii) displacement of the asphaltene network by adsorption of the more surface active copolymer into void sites at the oil/water interface. In order to reveal the mechanism of destabilisation, interactions between asphaltene aggregates and copolymer were explored. For that purpose various techniques have been employed: small angle X-ray scattering allowing the determination of the influence of copolymer on the size of asphaltene aggregate; capacity of copolymer to displace asphaltene aggregates initially adsorbed on silica particles (which simulate water droplets); Atomic Force Microscopy (AFM) was used to observe the influence of copolymer on the interfacial structure of asphaltene films spread on water surface.

Biosurfactants Production from Low Cost Substrate and Degradation of Diesel Oil by a Rhodococcus Strain

Abstract: The ability of a Rhodococcus strain to produce surface-active agents from residual sunflower frying oil (RSFO) has been screened in batch cultures. During cultivation with RSFO at the concentration 3% (vol/vol), the strain has synthesized extra-cellular compounds which increase the E24 emulsion index of the culture medium up to 63%. In their crude form, these substances lower the surface tension of water until 31.9 mN m-1 . The exponential growth with RSFO as the sole carbon source has developed at a specific growth rate μ = 0.55 d-1 . The critical micelle concentration of the crude product reached the value 287 mg L-1 (γ CMC = 31.9 mN m-1 ). After methylesterification, the lipid fraction of biosurfactants has been analyzed by GC-MS in EI, which reveals the presence of fatty acid methyl esters. The microorganism was also cultivated with the diesel oil as the sole carbon source at the concentration 1% (vol/vol): the active growth phase has developed at rate μ = 0.02 d-1 , without production of emulsifying substance: the microorganism seems to develop different modes of substrate uptake, according to the nature of the carbon source. The potential use of surface-active agents synthesized on RSFO by Rhodococcus erythropolis 16 LM.USTHB is in the oil industry with minimum purity specification, so that crude preparation could be used, at low cost, in clean-up of hydrocarbons contaminated sites and for enhanced oil recovery.

Characterization of Nitrogen and Sulfur Compounds in Hydrocracking Feedstocks by Fourier Transform Ion Cyclotron Mass Spectrometry

Abstract: Advanced characterization of two heavy hydrocracking unit feedstocks, Heavy Vacuum Gas Oil (HVGO) and De-Metallized Oil (DMO), both derived from Arabian Light crude oil, was performed using High Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) to gain in-depth information on their aromaticity characteristics and heteroatom content, i.e., sulfur- and nitrogen-compounds. In order to obtain chemically utilizable information, each individual mass signal in the high resolution mass spectra was linked to its underlying elemental composition, the relevant double bond equivalent (aromatic properties), and carbon number. The DMO differs from the VGO in the N-, and S-species distribution patterns. The DMO contains heavier and more condensed aromatic species than the HVGO. Species with up to three sulfur- and up to two nitrogen-atoms per molecule were found in both feedstocks. Nitrogen is present in both feedstocks in pyrrole- and pyridine-structures. Besides, numerous mono-, di-, and trisulfur species and acridines and carbazoles that contain 1 to 3 additional sulfur atoms in the same molecule were found in both feedstocks.

Comparison of Engine Calibration Methods Based on Design of Experiments (DoE)

Abstract: Due to more stringent emission and durability requirements as well as higher client-felt quality targets, engine technology and strategies used to control them are more and more complex. Car manufacturers need productive and reliable test facility as well as efficient methods and tools to address the challenge of tuning the increasing number of parameters related to these strategies, while reducing in the same development schedule and cost. In this context, IFP is developing methods to perform engine calibration, using a full automated test bench together with advanced mathematical methods for modeling and optimizing, as well as engine and vehicle simulation. The paper describes and compares the different approaches to perform the mapping of an engine on the NEDC area. Results obtained on a Common Rail Diesel engine are also presented to illustrate specific development works.

Irreducible Water Saturation from Capillary Pressure and Electrical Resistivity Measurements

Abstract: This paper presents the results of capillary pressure and electrical resistivity measurements for three kinds of core specimens: Berea sandstone, Quartz and Limestone. Experimental data of resistivity index, formation resistivity factor, tortuosity, capillary pressure, and water saturation exponent in the air/brine system for these cores are reported. The electrical resistivities data are evaluated using the modified Archie's law. Capillary pressure and electrical resistivity versus brine saturation results show the existence of two irreducible water saturations corresponding to two different physical phenomena. The two values of irreducible brine saturations yield upper and lower limits that can be used to estimate the production capacity of porous media. The detailed analysis of the data has also shown a change in the value of the saturation exponent. This change would be also be observed at the irreducible brine saturation as obtained with capillary pressure data.

Gas Turbine Performances Improvement using Steam Injection in the Combustion Chamber under Sahara Conditions

Abstract: Gas turbines are generally used for large scale power generation. The basic gas turbine cycle has low thermal efficiency which decreases in the hard climatic conditions of operation, so it is important to look for improved gas turbine based cycles. Among several methods shown their success in increasing the performances, the steam injected gas turbine cycle (STIG) consists to introduce a high amount of steam at various points in the cycle. The objective of the present work is to improve the performances of gas turbine used under Sahara conditions by injecting suitable quantities of steam in the upstream of combustion chamber. The suggested method has been studied and compared with a simple cycle. Efficiency, however, is held constant when the ambient temperature increases from iso conditions to 50C. Computer program has been developed for various gas turbine processes including the effect of ambient temperature. This is achieved by studying the effect of steam injection on the gas turbine performances. Data from the performance testing of an industrial gas turbine, computer model and theoretical study are used to check the validity of the proposed model. The comparison of the prediction results to the test data is in good agreement.

Fatty Acid Esters in Europe: Market Trends and Technological Perspectives

Abstract: Based on strong governmental incentives, biodiesel from transesterification of Fatty Acids (FAE) production is rapidly increasing mainly in Europe and is starting to expand worldwide. A closer look at the complex European incentives scheme and an update of the planned FAE capacity expansion helps to explain the key economic factors in this sharp raise in FAE activity. Based on this economic background, key factors for FAE technology selection will be explored to demonstrate alternatives for biofuels production. Increasing biodiesel consumption in a sustainable way requires optimizing production processes compatible with high production capacities, high yields and low environmental impact, especially regarding wastes streams. This paper highlights a commercially proven technology available for meeting these challenges, focusing on a new continuous FAE production process where the transesterification reaction is promoted by a heterogeneous catalyst. This process employs methanolysis of vegetable oils by passing the reactants through two consecutive fixed-bed reactors followed by methanol and glycerin separation stages. The Axens process requires neither catalyst recovery nor aqueous treatment. It achieves very high methyl esters yields with a high purity glycerin byproduct. At least 98% purity glycerin is directly recovered in the total absence of any mineral (salts) contaminants thereby offering an alternative for a real “Green Process”.

Underground Gas Storage in a Partially Depleted Gas Reservoir

Abstract: In this work, underground gas storage (UGS) was studied on a partially depleted gas reservoir through compositional simulation. Prediction of reservoir fluid phase behavior and history matching was done by utilizing detailed reservoir information. The performance of UGS with different scenarios of reservoir depletion, gas injection, and aquifer strength was analyzed. The injection capacity and deliverability of reservoir was set to 350 MMSCF/D (6 months) and 420 MMSCF/D (5 months), respectively. Based on different scenarios and the anticipated target rate, the optimum pressure for converting this reservoir to UGS was found to be about 1600 psia. Also, it was found that if the reservoir is depleted to a lower pressure, it contains insufficient base gas reserve and may not meet the target withdrawal rate. Results showed that this problem can be overcome by injecting higher volume of gas in the first cycle. Furthermore, it was shown that an active aquifer can lead to irreversible reservoir shrinkage, increase in water-gas ratio, and pressure rise in reservoir. Another source of pressure rise during the UGS operations is the difference between z-factors of injected and reservoir fluids. It was found that injecting lean gas with high z-factor into a reservoir containing fluid of lower z-factor results in pressure rise at the end of each cycle. At successive cycles, composition of reservoir fluid approaches that of the injected gas because of continual mixing. Theoretically, composition of reservoir fluid will be near the injected fluid after infinite cycles, provided complete mixing occurs in reservoir. Under these conditions, difference between z-factors of injected and reservoir fluids become smaller, and reservoir pressure stabilizes.

3D Seismic Imaging of a Near-Surface Heterogeneous Aquifer: A Case Study

Abstract: Different surface seismic surveys have been recorded on an experimental hydrogeological site that has been developed for several years near Poitiers (France). The paper shows how 3D seismic imaging can be used to describe the near-surface heterogeneous aquifer. The acquisition spread is designed to perform both 3D refraction and reflection seismic surveying. Refraction survey enables us to obtain a 3D image in depth of a low velocity superficial zone contrasting with the underlying water – bearing carbonates. Variogram analysis and geostatistical filtering allow to filter random and structured acquisition noise. Factorial kriging is used to filter the small scale structures (cubic structure with a range of 55 m and nugget) in order to make the large scale structures appear and to determine their orientation: a main orientation N90 and a secondary orientation N50. These two directions have been selected to implement two deviated wells C3 and C4. Reflection survey enables us to get a 3D seismic pseudo velocity block in depth. The vertical resolution is enhanced thanks to deconvolution after depth conversion. A Wiener filter, defined at a reference well C1 has been applied to the seismic traces to convert into velocity the amplitude sections. The results obtained are validated at four wells (MP6, MP5, M8, M9) in which acoustic data have been recorded. The 3D seismic pseudo velocity block shows the large heterogeneity of the aquifer reservoir in the horizontal and vertical planes, confirms the main structural orientations (N90 and N50) pointed out by refraction survey. At a given depth, the velocity distribution shows preferential connections between wells. As an example, well pumping tests and pressure interference confirm the hydrodynamic connection between wells M13 and M21 defined by a low velocity zone at 88 m depth.

Study of the VAPEX Process in Fractured Physical Systems Using Different Solvent Mixtures

Abstract: In this work, the vapour extraction (VAPEX) process is studied experimentally in a rectangular physical model at moderate-high pressure. The solvent was either pure propane or a mixture of propane/methane with different compositions. The solvent and carrier gas were totally mixed before injection, so that a solvent with the desired composition flowed through the injector during experiments, and the solvent mixture was in thermodynamic equilibrium before injection into VAPEX cell. Effects of pressure and composition of solvent were studied. Results showed that at a fixed pressure, the process is more effective with pure solvent compared to the use of solvent mixtures. The main feature of this work is that heavy oil recovery is improved as the approach pressure, defined as the (saturation) pressure minus operating pressure, decreases regardless of solvent composition or operating pressure. These results provide insight into proper field scale implementation of the VAPEX process.

Differential-Algebraic Approach to Dynamic Simulations of Flash Drums with Rigorous Evaluation of Physical Properties

Abstract: Differential-Algebraic Approach to Dynamic Simulations of Flash Drums with Rigorous Evaluation of Physical Properties — The dynamics of flash drums is simulated with rigorous physical properties calculations using an equation of state to model each phase present. The formulation results in a set of differential-algebraic equations (DAE), whose differential equations describe the material and energy balances and the algebraic equations result from the conditions for thermodynamic equilibrium inside the drum. PSIDE (Parallel Software for Implicit Differential Equations) (Lioen et al., 1998) is used to solve the set of DAE with an efficient differential-algebraic approach. In this approach, the equations are solved simultaneously, with direct iterations in temperature, phase volumes and mole number of each component in each phase. The results show the efficiency of this methodology for the simulation of flash drums.

An Investigation of Unburned Hydrocarbon Emissions in Wall Guided, Low Temperature Diesel Combustion

Abstract: The formation mechanisms of unburned hydrocarbons (HC) in low NOx, homogeneous type Diesel combustion have been investigated in both standard and optical access single cylinder engines operating under low load (2 and 4 bar IMEP) conditions. In the standard (i.e. nonoptical) engine, parameters such as injection timing, intake temperature and global equivalence ratio were varied in order to analyse the role of bulk quenching on HC emissions formation. Laser-Induced Fluorescence (LIF) imaging of in-cylinder unburned HC within the bulk gases was performed on the optical-access engine. Furthermore, studies were performed in order to ascertain whether the piston topland crevice volume contributes significantly to engine-out HC emissions. Finally, the role of piston-top fuel films and their impact on HC emissions was studied. This was investigated on the all-metal engine using two fuels of different volatilities. Parallel studies were also performed on the optical-access engine via in-cylinder tracer Laser-Induced Fluorescence (LIF) imaging. Results obtained in the standard and optical access engines revealed that bulk quenching represents one of the most significant sources of unburned HC for the wall guided combustion chamber geometry. Bulk quenching occurs as a result of incomplete fuel oxidation reactions in regions where the local equivalence ratio is either too fuel-lean or too fuel-rich or alternatively in excessively low temperature zones within the combustion chamber. Experimental data obtained from both the standard and optical access engines also revealed that liquid film formation occurs, and is particularly prevalent for early Start Of Injection (SOI) strategies. Furthermore, liquid films remain present at the end of combustion and are believed to represent a significant source of engine-out HC emissions. In-cylinder imaging of liquid films suggest that the film eventually detaches from the piston surface later during the expansion stroke, resembling a flash boiling phenomenon. The results appear to confirm that unburned fuel arising from piston-top fuel films contribute directly to the engine-out HC emissions.

Oil Seeps from the Boulganack Mud Volcano in the Kerch Peninsula (Ukraine -Crimea), Study of the Mud and the Gas : Inferences for the Petroleum Potential

Abstract: Mud volcanoes act as prospecting indices in the exploration of oil and gas deposits with gases and muds excreted. A methodology and an analytical protocol have been developed in order to classify the petroleum provinces according to the geochemical information available from the mud volcanoes. Such a study allows us to evaluate the potential of the petroleum system beneath. The Crimean-Caucasus region is renowned for mud volcano activity with well-known areas from west to east: Kerch Peninsula, Kuban and Azerbaijan. A methodology concerning the geochemical sampling and analysis of the mud volcanoes located onshore was applied to the Kerch Peninsula. Three field trips were organised by IFP in 2000, 2001 and 2002 in order to collect geochemical data, in agreement with the Museum of National History in Kiev. During these geological and geochemical surveys particular attention was given to the Boulganack mud volcano, which is a favourable site for the study of mud and gas samples due to the variety of the types of the vents. Specific tools were built in order to take samples of mud, up to 20 m deep in the vents, and gas more than 25 m away from the bubbling point in safe conditions in the deep mud lakes. Moreover, monitoring of the sampling of the gas was undertaken on the Boulganack mud volcano for one year in order to study the variation in the composition of the gas in time and space in the various vents. The proportions of nitrogen, carbon dioxide and hydrocarbons (methane to ethane) were measured. The vents of the Boulganack mud volcano present about 90% of methane and 10% CO2 , with a few percent of heavier hydrocarbons in one particular vent: Andrusov. Pavlov expelled more CO2 (25% to 40%), with the greatest temporal variations. Only Obrudchev expels as much carbon dioxide as methane (50/50). Sometimes, nitrogen was also measured (Pavlov, Obrudchev and Central Lake). The high dryness of the gas implies a loss of heavy hydrocarbon compounds relative to a typical thermogenic gas. Chemical gas compounds are highly dependent from one vent to the other. The comparison of the quantity of hydrocarbon included in the mud released from the mud volcanoes of the Kerch Peninsula and those of Azerbaijan (used as a reference) shows very little hydrocarbon in the mud from the mud volcano in the Crimea, whereas accumulations of hydrocarbons exist in the fluids expelled from mud volcanoes in Azerbaijan. In fact, the ranking of the petroleum provinces is linked to the occurrence of the free hydrocarbons in the mud excreted by mud volcanoes. Analysis by chromatography of the saturated hydrocarbons presents a high degree of biodegradation when the samples are taken at the surface. When they are taken with the core barrel at greater depth in the vents, the hydrocarbons are preserved with a typical continental origin which can be compared with the organic matter of the Maykop formation. The modelling of the hydrocarbon window geohistory confirms that the hydrocarbons are mainly produced within the lower Maykop. The generation of gas is favoured, in agreement with the quality of the type III source rocks in this western part of the Caucasus.

The pentane- and toluene-soluble fractions of a petroleum residue and three coal tars by size exclusion chromatography and UV-fluorescence spectroscopy

Abstract: A petroleum atmospheric pressure distillate residue and three tars derived from different coals using different severities of thermal treatment were separated into seven fractions using column chromatography on silica and sequential elution by the solvent sequence pentane, toluene, acetonitrile, pyridine, 1-methyl-2-pyrrolidinone (NMP) and water. The fractions from the four extractions have been compared using size exclusion chromatography (SEC) in NMP as eluent and by synchronous ultra-violet-fluorescence (UV-F). This paper concerns the pentane and toluene soluble fractions only since these are the least polar fractions. By SEC, the size of the aromatic molecules increased from the first pentane soluble fractions to the toluene-soluble fractions, with the petroleum residue fractions of larger size than the equivalent fractions from coal liquids. The three coal tars showed significant differences, indicating that temperature of pyrolysis had a significant effect on the molecular size. Synchronous UV-F spectra of the four sets of fractions, in solution in NMP, again showed significant differences between the petroleum residue and the coal tars, as well as amongst the three coal tars. In general, the petroleum residue fractions contained smaller aromatic clusters than the coal liquid fractions. These low-polarity fractions contained material excluded from the column porosity in SEC that was unlikely to consist of aggregates of polar molecules.

Developing Correlations for Prediction of Petroleum Fraction Properties using Genetic Algorithms

Abstract: This paper deals with the characterization of petroleum fractions whose thermo-physical behaviours can only be known through expensive measurement efforts due to the multiplicity of their constituents. After introducing the issue and new trends in the use of artificial intelligence techniques, this paper shows how genetic algorithms can be applied to this field. Hence, we propose an empirical approach for estimating petroleum fractions critical properties and acentric factor based on their boiling point and density that can be easily obtained. Genetic algorithms provide us with a proper function form for the prediction. Moreover, very promising results are obtained and several relevant issues that deserve further investigations are emphasized.

Variable Valve Actuation Systems for Homogeneous Diesel Combustion: How Interesting are They?

Abstract: With a high thermal efficiency and with low CO2 (carbon dioxide) emissions, Diesel engines would become leader of tomorrow's transport market. However, the evolution of the regulatory constraints leads to a drastic reduction of their NOx (nitrogen oxide) and particulate emissions. Another interesting competitor to the NOx after-treatment systems is the use of new combustion concepts to reduce the raw emissions: homogeneous combustion (Homogeneous Charge Compression Ignition - HCCI- or Highly Premixed Combustion - HPC). Nonetheless, such concepts present non negligible drawbacks such as a limited zero NOx operating range, huge external gas recirculation (EGR) needs which forces a complete redesign of the air path circuit maintaining a high level of full load performances, and above all excessive HC (unburned hydrocarbon) and CO (carbon monoxide) emissions at low load. The emerging Variable Valve Actuation technologies (VVA) could totally change the deal of the new combustion processes especially through the internal EGR possibilities and the effective compression ratio reduction. Through the well known dual mode HCCI combustion concept NADI™ developed by IFP, this paper aims at evaluating the improvement potential of this kind of combustion concept with the use of several intake and exhaust VVA configurations and makes a comparison between these approaches. The results come from a single cylinder engine equipped with a fully variable intake and exhaust VVA (camless). After a brief description of the VVA system and the possibilities offered, two aspects of the potential are studied: – the different ways to obtain internal EGR and its main interests with the high potential to reduce HC and CO emissions at low load in homogeneous combustion (HCCI or HPC): 70% reduction on the HC emissions, 40% on CO emissions keeping same NOx emissions level; – the effective compression ratio reduction with a view to increase the maximum load with very low NOx emissions. First, the ways to reduce the effective compression ratio are presented and then, the reduced possibilities given in this field due to decrease of air flow are analysed.

Global Airpath Control for a Turbocharged Diesel HCCI Engine

Abstract: A motion planning based control strategy is proposed for the airpath control of turbochargedDiesel engines using Exhaust Gas Recirculation (EGR). The considered model uses simple balance equations. The fully actuated dynamics are easily inverted, yielding straightforward open-loop control laws. This approach is complemented by experimentally derived look-up tables to cast the drivers requests into transients between operating points. Moreover, a turbocharging control strategy is developed to provide the required amount of fresh air taking into account the turbocharger dynamics. Experimental tests are reported on a 4-cylinder engine in Homogeneous Charge Compression Ignition (HCCI) mode. Conclusions stress the possibility of taking into account the non minimum phase effects of this system by a simple, yet efficient, control law. Realized transients are fast and accurate.

Quantitative Pollutant Modelling: an Essential Prerequisite for Diesel HCCI and LTC Engine Design

Abstract: To face the demand for efficient and environmentally-friendly engines, the Diesel HCCI (Homogeneous Charge Compression Ignition) and LTC (Low Temperature Combustion) concepts have been developed in order to drastically reduce the pollutant emissions of present Diesel engines at part load while maintaining their fuel consumption attractive. To be useful in the optimisation procedure of such new engine concepts, 3D CFD (Computational Fluid Dynamics) simulation softwares have to be predictive in terms of consumption and pollutants not only qualitatively (emphasising the global trends) but also quantitatively (providing reliable numbers to allow design or strategy comparisons). The implementation of accurate predictive combustion and pollutant models in 3D CFD codes are consequently a prerequisite to the use of these simulation tools to develop new combustion chamber designs or to test unconventional operating strategies. Pollutant modelling is a very difficult task because the pollutant formation and conversion during and after combustion heavily depend on the mixture formation and combustion processes that define the initial conditions for their complex chemical reactions. Furthermore, the occurring complex chemical reactions are far from being totally known. The correct prediction of the mixture formation and combustion processes are therefore essential for a correct pollutant prediction. However, the complex chemistry controlling the pollutant formation needs to be reduced to propose models that give accurate results with a reasonable CPU time consumption. For the HCCI and LTC engine concepts, the operating restrictions are mainly the NOx /soot trade-off and the noise level. The noise level may be related to the pressure rise and its prediction will therefore be a matter of accurate combustion description. On the other hand, the NOx /soot trade-off can only be numerically handled if accurate pollutant models are available. In the present study, the NOx model is the extended Zeldovitch model while the soot model is the PSK (Phenomenological Soot Kinetics) model coupled with the CORK (CO Reduced Kinetics) model to ensure a correct energy balance.

Development of a Coupling Approach between 0D D.I. Diesel Combustion and Pollutant Models: Application to a Transient Engine Evolution

Abstract: The constant increase in pollutant emissions constraints has obliged automotive manufacturers to adopt a global optimization approach of engine and exhaust after-treatment technology Engine control strategies appear to be a powerful solution to address this issue The problem is particularly complex since acceptable drivability must be maintained whilst at the same time reducing in-cylinder pollutant emissions and ensuring optimum conditions to attain highconversion efficiencies via exhaust gas after-treatment systems The development of appropriate control strategies can only be achieved with an in-depth understanding of the engine behaviour, using experimental results and system numerical simulations In this context, predictive combustion and pollutant emissions models, which are calibrated with experimental data, are particularly useful as they allow a wide range of parametric variations to be studied This paper presents an advanced Diesel combustion model based on a Barba's approach [Barba C et al (2000)- A Phenomenological Combustion Model for Heat Release Rate Prediction in High Speed DI Diesel Engines with Common Rail Injection , SAE Technical Paper 2000-01-2933] This model can be applied to multi-injection, defining a pre-mixed combustion zone for the pilot injection and a diffusion combustion mode for the main injection To assess the in-cylinder pollutant emissions, a mixing model based on the turbulent kinetic energy generated by the spray, is added to define a burnt gas zone in which post-flame chemistry including CO, NOx and soot formation can be computed This model is first validated using CHEMKIN and 3D CFD results Then, using experimental results, a 4 cylinders DI Diesel engine is calibrated on steady state engine operating conditions and coupled to an engine control to predict the evolution of pollutant emissions under transient conditions

Description of the Thermodynamic Properties of Aqueous Ionic Solutions within the Mean Spherical Approximation

Abstract: The thermodynamic properties of ionic solutions are described within the mean spherical approximation (MSA). The original MSA and binding MSA (BiMSA) have been supplemented so as to include solvation effects. The model is shown to be capable of representing ionic solution thermodynamics in a wide range of concentration, generally up to saturation, in the case of strong and associating electrolytes. It constitutes an interesting alternative to the Pitzer model.

3D Confocal Scanning Laser Microscopy to Quantify Contact Angles in Natural Oil-Water Mixtures

Abstract: The contact angle of a liquid drop on a solid surface is one of the most simple, useful and sensitive parameters in the hydraulic sciences to quantify and to qualify the wettability and the surface energy of different materials. In this paper, a confocal scanning laser microscope (CSLM) has been used to quantify contact angle and then the wettability. This technique uses a laser scan and allows series of 2-D images of a fluorescent liquid droplet set on various solid surfaces to be recorded. The generation of 3-D images is carried out with the summation of several images acquired with a regular step along the CSLM z-axis. The results obtained are compared and discussed with those obtained with a conventional goniometric technique for different solid-liquid-air systems. CSLM results show that similar values are obtained with both methods. Thus, this technique shows that the length interval of sampling between the solid contact and the curvature rupture of the drop seems to be essential to correctly estimate the contact angles. This method allows the study of the local contact angle along the periphery of the drop, and the deformation of the drop shape. Construction of 3-D images shows that drops are characterized by complex morphologies and that the local contact angles can be modified by chemical heterogeneities in the fluids.

Development of Optical Diagnostic Techniques to Correlate Mixing and Auto-Ignition Processes in High Pressure Diesel Jets

Abstract: A tracer laser-induced fluorescence (LIF) technique for the visualization of fuel distribution in the presence of oxygen was developed and then used sequentially with high speed chemiluminescence imaging to study the correlation between the mixing and auto-ignition processes of high pressure Diesel jets. A single hole common rail Diesel injector allowing high injection pressures up to 150 MPa was used. The reacting fuel spray was observed in a high pressure, high temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a Diesel engine during injection. Both free jet and flat wall impinging jet configurations were studied. Several tracers were first considered with the objective of developing a tracer-LIF technique in the presence of oxygen. 5-nonanone was selected for its higher fluorescence efficiency. This technique was subsequently combined with high speed chemiluminescence imaging to study the correlation between mixing and auto-ignition. In the free jet configuration and for the parameter range studied, it was found that auto-ignition is preferentially located in rich regions of the upstream mixing zone. Also, in the jet wall configuration, auto-ignition appears in the centre of the jet and propagates towards the periphery, in the vicinity of the wall.

Liquid Drying by Solid Desiccant Materials: Experimental Study and Design Method

Abstract: The use of consumable solid desiccant materials for organic liquid dehydration is very current in refinery or chemistry processes, especially when the water concentration is very low (<1000 ppm). In spite of its common use, the kinetics of liquid drying by solid desiccants is not well known, and scale-up of industrial drying processes using such materials is always problematic. In this study, the kinetics of drying of two organic liquids, dipropylene-glycol (DPG) and toluene, with some classical “type-1” desiccant materials is analysed. The experiments were done on three different scales, by using different appropriate apparatus: a laboratory stirred reactor, a small pilot and a semi-industrial pilot. The results show that dehydration kinetics is driven by a strong mass transfer limitation. Based on these results, a simple model is developed in order to design industrial drying columns from pilot data. This model is able to predict the time evolution of the water content at the outlet of the column, and the resulting simulations are in good agreement with experiments.