The most cited articles published since 2010, extracted from Scopus
Volume 2, Issue 1, March 2010, Pages 49-59
Yu F. Makogon
Gas hydrates are clathrate physical compounds, in which the molecules of gas are occluded in crystalline cells, consisting of water molecules retained by the energy of hydrogen bonds. All gases can form hydrates under different pressures and temperatures. The crystalline structure of solid gas hydrate crystals has a strong dependence on gas composition, pressure, and temperature. Presently, three crystalline structures are known (Sloan, 1990, 2007) to form at moderate pressure, and nearly ten structures in the pressure range above 100 MPa. For example, methane hydrate can be stable at a pressure of 20 nPa to 2 GPa, and at temperatures changing from 70 to 350 K (Makogon, 1997). Formation of gas hydrate occurs when water and natural gas are present at a low temperature and a high pressure. Such conditions often exist in oil and gas wells, and pipeline equipment. Hydrate plugs can damage gas transport system equipment. The petroleum industry spends about one billion US dollars a year to prevent hydrate formation in wells, pipelines and equipment. Natural deposits of gas hydrates also exist on Earth in colder regions, such as permafrost, or sea bottom areas. Natural gas hydrates are an unconventional energy resource. Potential reserves of gas in hydrated posits distributed offshore and on land are over 1.5 × 1016 m3 (Makogon, 1982). About 97% of natural gas hydrates have been located offshore, and only 3% on land. At present time, there are several successful federal research programs in a number of countries for research and development of gas hydrate deposits. Over 230 gas hydrate deposits were discovered, over a hundred wells drilled, and kilometers of cores studied. Gas hydrate resource is distributed conveniently for development by most every country. Effective tools for the recovery of gas from hydrate deposits, and new technology for development of gas hydrate deposits are being developed. There is a commercial production of natural gas from hydrates in Siberia. Researchers continue to study the properties of natural gas hydrates at reservoir conditions, and develop new technologies for exploration and production of gas from hydrate deposits in different geological formations. © 2009.
Volume 3, Issue 2, May 2011, Pages 423-459
Kim Aasberg-Petersen | Ib Dybkjær | Charlotte V. Ovesen | Niels Christian Schjødt | Jens Sehested | Søren Gyde Thomsen
Natural gas is a dominating feedstock for the production of several bulk chemicals such as ammonia, methanol, and dimethyl ether (DME), and for the increasingly important production of synthetic liquid fuels by Fischer-Tropsch synthesis (FT synthesis) and similar processes.A major step in the conversion of natural gas to products is the production of synthesis gas with the desired composition - ranging from the 3:1 mixture of hydrogen and nitrogen used for production of ammonia to the 1:1 mixture of hydrogen and carbon monoxide preferred for production of DME.Catalysts and catalytic processes are important in the production of synthesis gas from natural gas. As an example, production of ammonia synthesis gas may in modern plants involve up to 8 separate catalytic process steps.In the article, relevant catalytic technologies are reviewed with emphasis on the present status and possible future developments. The relevant technologies are:. •Final feed gas purification•Adiabatic prereforming•Fired tubular reforming•Heat exchange steam reforming•Adiabatic, oxidative reforming, mainly autothermal reforming (ATR) and secondary reforming•Other reforming technologies such as Catalytic Partial Oxidation (CPO) and Ceramic Membrane Reforming (CMR).•Conversion of carbon monoxide to carbon dioxide by the shift reaction•Final purification of synthesis gas, mainly removal of nitrogen compounds and removal of carbon oxides by methanation.After the discussion of the individual catalysts and catalytic process steps, applications are illustrated by summary descriptions of complete process concepts for production of ammonia, methanol, and hydrocarbons by low temperature FT synthesis (GTL). In a final section, future trends in the area are briefly discussed. © 2011.
Volume 9, Issue , November 2012, Pages 196-208
David A. Wood | Chikezie Nwaoha | Brian Francis Towler
Gas-to-liquids (GTL) has emerged as a commercially-viable industry over the past thirty years offering market diversification to remote natural gas resource holders. Several technologies are now available through a series of patented processes to provide liquid products that can be more easily transported than natural gas, and directed into high value transportation fuel and other petroleum product and petrochemical markets. Recent low natural gas prices prevailing in North America are stimulating interest in GTL as a means to better monetise isolated shale gas resources. This article reviews the various GTL technologies, the commercial plants in operation, development and planning, and the range of market opportunities for GTL products. The Fischer-Tropsch (F-T) technologies dominate both large-scale and small-scale projects targeting middle distillate liquid transportation fuel markets. The large technology providers have followed strategies to scale-up plants over the past decade to provide commercial economies of scale, which to date have proved to be more costly than originally forecast. On the other hand, some small-scale technology providers are now targeting GTL at efforts to eliminate associated gas flaring in remote producing oil fields. Also, potential exists on various scales for GTL to supply liquid fuels in land-locked gas-rich regions. Technology routes from natural gas to gasoline via olefins are more complex and have so far proved difficult and costly to scale-up commercially. Producing dimethyl ether (DME) from coal and gas are growing markets in Asia, particularly China, Korea and Japan as LPG substitutes, and plans to scale-up one-step process technologies avoiding methanol production could see an expansion of DME supply chains. The GTL industry faces a number of challenges and risks, including: high capital costs; efficiency and reliability of complex process sequences; volatile natural gas, crude oil and petroleum product markets; integration of upstream and downstream projects; access to technology. This review article considers the GTL industry in the context of available opportunities and the challenges faced by project developers. © 2012 Elsevier B.V.
Volume 2, Issue 4, September 2010, Pages 197-210
Yu Wu | Jishan Liu | Derek Elsworth | Xiexing MIAO | Xianbiao Mao
Although coal-gas interactions have been comprehensively investigated, prior studies have focused on one or more component processes of effective stress in driving only isotropic changes in coal permeability. In our previous work (Wu et al., 2009) a general porosity and permeability model was developed to represent the behavior of both the primary medium (coal matrix) and the secondary medium (fractures) under conditions of variable stress. In this study the permeability model is extended to define the evolution of gas sorption-induced permeability anisotropy under the full spectrum of mechanical conditions spanning prescribed in situ stresses through constrained displacement. These models are implemented into a fully coupled model of coal deformation, gas flow and transport in the matrix system, and gas flow and transport in the fracture system. The model separately accommodates compressible gas flow and transport in the coal matrix and fracture systems and rigorously accommodates the role of mechanical deformations for a dual-porosity continuum. Since mechanical interactions and the role of sorption-induced strains are rigorously accommodated, these micro-mechanical models are capable of following the evolution of porosity and permeability in both the coal matrix and the fracture network. This model represents important non-linear responses due to the effective stress effects that cannot be recovered where mechanical influences are not rigorously coupled with the transport system. The permeability model for fractures is verified against the analytical solution for a constant volume reservoir and applied to successfully match a suite of field data from the San Juan Basin. The fully coupled model for coal deformation and gas flow has been applied to quantify the impacts of fracture spacing and in situ ground stresses on coal properties and active processes: those involving shrinkage, swelling and direct changes in effective stress. Model results demonstrate the complex interactions of fracture-matrix induced by CBM production. © 2010 Elsevier B.V.
Volume 9, Issue , November 2012, Pages 94-107
Theo H. Fleisch | Arun J. Basu | Ron A. Sills
The last two decades saw the emergence of a new multi-source, multi-market fuel, Dimethyl Ether or DME. Prior to 1990, DME had only found limited commercial use as an aerosol propellant along with propane and butane as a green replacement for the chlorofluoro-hydrocarbons which were outlawed because of their detrimental impact on the ozone layer. DME is an environmentally benign, non-toxic, biodegradable product with physical properties similar to LPG. Global DME annual production capacity is approximately 10 million metric tons and actual market use is reported to be about 3 million metric tons - a remarkable increase from the 200,000 metric tons market demand in the early 2000s. Nearly all of the DME is produced in China from coal-derived methanol via the well known catalytic dehydration process where two molecules of methanol react to form one molecule of DME and one molecule of water. DME is the fastest-growing methanol derivative, yet is still an emerging business with lots of upside opportunities combined with significant challenges. A number of other DME plants are in different stages of development around the world including Egypt, Middle East and Indonesia, all of them natural gas based. Sweden is the leader in the development of bio-DME produced through the gasification and conversion of black liquor, a byproduct in Sweden's paper and pulp industry. Nearly all of today's DME is used as a blend stock for LPG which in turn is primarily used for cooking and heating. At blending levels below 20 vol %, the existing LPG blending facilities, local distribution infrastructure and end-use equipment can be used with minimal (if any) modifications - making for easy marketing. Currently, efforts are underway to commercialize DME as a high-quality diesel alternative. Technical issues such as new fuel injection systems and new fuel additives have been solved and solutions are currently being tested in fleets. This review will describe the history, status and future of DME as a global fuel alternative and how it has and will be changing the global methanol industry. © 2012 Elsevier B.V.
Volume 2, Issue 1, March 2010, Pages 41-48
Abdelsalam Sarkhi Al-Sarkhi
A literature survey of the published work on drag reduction by Drag Reducing Agent (DRA) in two-phase flow is reviewed. Characteristics of the two-phase flow with drag reducing additives are described and the research approaches and methodology concerning drag reduction with additives in multiphase flow is introduced. Suggested mechanisms for drag reduction phenomena and procedure in two-phase flow are discussed. Some of the industrial application of the use of drag reducing additives in two-phase flow is explained. Finally, Recommendations, new suggested approaches for future research needs and potential areas that need further research is highlighted. © 2010 Elsevier B.V. All rights reserved.
Volume 3, Issue 4, September 2011, Pages 571-580
Ivar Johan Halvorsen | Sigurd Skogestad
Distillation is responsible for a significant amount of the energy consumption of the world's process industry and also in the natural gas processing. There is a significant energy saving potential that can be obtained by applying new energy saving distillation technology that has appeared in the last two decades. The fully thermally coupled dividing wall columns have the attractive feature of both savings in energy consumption and reduction of investment cost. In this paper we give an overview of some energy saving distillation arrangements and show how the Vmin-diagram can be used to assess separations and calculate energy requirements and provide a basis for detailed design. Reduced CO2 emission is an additional benefit that actually comes for free by the reduction of energy consumption. © 2011 Elsevier B.V.
Volume 3, Issue 2, May 2011, Pages 382-401
Christopher R. Clarkson | J. J. Beierle
Quantitative production analysis of tight gas reservoirs has historically been a challenge due to complex reservoir characteristics (ex. lateral and vertical heterogeneity, stress-sensitivity of permeability and porosity), induced hydraulic fracture properties in vertical wells (ex. multi-phase flow, conductivity changes, complex fracture geometries), operational complexities (ex. variable back-pressure, liquid-loading) and data quality (infrequent rate or flowing pressure reporting). All of these challenges conspire to make extraction of reservoir (kh and OGIP) and hydraulic fracture properties (xf and fracture conductivity) soley from production/flowing pressure data difficult, often resulting in non-unique answers. In recent history, there has been the added complication that tight gas (and most recently shale gas) reservoirs are now being exploited with horizontal wells, often stimulated using multiple hydraulic fracture stages, which imparts greater complexity on the analysis. Flow regime identification, which is critical to the correct analysis, is more complicated than ever owing to the number of possible flow regimes encountered in such wells.A case study is presented in which it is demonstrated that modern post-fracture surveillance data, such as microseismic and post-frac production logging, aids in both model identification and model calibration, which is critical to the analysis of hydraulically-fractured horizontal wells completed in tight gas formations. A workflow is presented in which offset vertical wells (to the horizontal wells) are first analyzed to obtain estimates of kh and hydraulic fracture properties, followed by commingled stage and single-stage production analysis of the multi- (transverse) hydraulic fracture horizontal wells. Microseismic data is incorporated into the analysis of the horizontal wells to 1) understand the orientation and degree of complexity of the induced hydraulic fractures and 2) constrain interpretations of effective hydraulic fracture lengths from production data analysis. It is also demonstrated that once the commingled stage analysis of the horizontal wells is completed, the total interpreted effective hydraulic fracture half-length may be allocated amongst the stages using a combination of production logs and tracer logs.The primary contribution of the current work is the presentation of workflows, emphasizing the integration of various data sources, to improve production analysis of multi-frac'd horizontal wells completed in tight gas formations. In addition to the workflows, it is shown that a combination of advanced production analysis approaches, including methods analogous to classic pressure transient analysis, production type-curve matching and simulation, may be necessary to arrive at a unique analysis. © 2011 Elsevier B.V.
Volume 3, Issue 1, March 2011, Pages 356-363
Antonio Messineo | GIUSEPPE Panno
It is known how the complete gasification of liquefied natural gas (LNG) can return about 230 kWh/t of energy. Nevertheless out of fifty-one gasification plants in the world, only thirty-one of them are equipped with systems for the partial recovery of the available energy. At the moment most of these plants mainly produce electric energy; however the employment of the cold energy results very interesting, in fact, it can be recovered for agro-food transformation and conservation as well as for some loops in the cold chain. Cold energy at low temperatures requires high amounts of mechanical energy and it unavoidably increases as the required temperature diminishes. Cold energy recovery from LNG gasification would allow considerable energy and economic savings to these applications, as well as environmental benefits due to the reduction of climate-changing gas emissions. The task of this work is to assess the possibility to create around a gasification plant an industrial site for firms working on the transformation and conservation of agro-food products locally grown. The cold energy recovered from gasification would be distributed to those firms through an opportune liquid carbon dioxide network distribution capable of supplying " the cold" to the different facilities. A LNG gasification plant in a highly agricultural zone in Sicily would increase the worth of the agro-food production, lower transformation and conservation costs when compared to the traditional systems and bring economic and environmental benefits to the interested areas. © 2011 Elsevier B.V.
Volume 8, Issue , September 2012, Pages 132-138
Carolyn Koh | Amadeu Sum | Earl Dendy Sloan
An overview is provided of hydrates in nature manuscripts among the 800 papers of the Seventh International Conference on Gas Hydrates (Edinburgh, July 17-22, 2011), to demonstrate the basic chemico-geophysics, as well as a perspective on hydrates as a resource activity by each country.The following summarizes the current status of gas hydrates as a natural resource: (1) there is substantial methane in hydrates, (2) the most accessible hydrates are in sandy sediments, with lithological controls, (3) laboratory characterization tools are available, (4) field detection tools are acceptable, (5) many of the national programs are in the phase of resource identification and characterization, with two exceptions, and (6) the first long-term production tests of methane hydrates will likely start in 2012 in the North Slope permafrost, and offshore Japan. © 2012 Elsevier B.V.
Volume 3, Issue 3, July 2011, Pages 505-517
Fatai Adesina Anifowose | Abdulazeez Azeez Abdulraheem
This work demonstrates the capabilities of two hybrid models as Computational Intelligence tools in the prediction of two important oil and gas reservoir properties, viz., porosity and permeability. The hybrid modeling was based on the combination of three existing Artificial Intelligence techniques: Functional Networks, Type-2 Fuzzy Logic System, and Support Vector Machines, using six datasets by utilizing the functional approximation capabilities of Functional Networks, the ability of Type-2 Fuzzy Logic to handle uncertainties and the scalability and robustness of Support Vector Machines in handling small and high-dimensional data. The hybridization was done in a way that allows one technique to further improve on the output of the other. Various Artificial intelligence techniques have been used in the prediction of oil and gas reservoir properties but each technique have exhibited specific capabilities, demonstrated certain limitations and posed a number of challenges. They have proven clearly that no single technique is perfect in all situations; hence the need for hybrid models that will combine the best characteristics of each technique in a single package and in the process, increase the confidence in the prediction of various oil and gas reservoir properties. This will result in increased production of more crude oil and hydrocarbons to meet the increasing world's demand. The results showed that the hybrid models perform better with higher correlation coefficients than the individual techniques when used alone for the same sets of data. In terms of execution time, the hybrid models took less time for both training and testing than the Type-2 Fuzzy Logic, but more time than Functional Networks and Support Vector Machines. This could be the price to pay for having better and more robust models. This work has demonstrated a successful application of the hybridization of three Artificial Intelligence techniques in one of the real-life problems encountered in oil and gas production where high quality information and accurate predictions are required for better and more efficient exploration, resource evaluation and their management. © 2011 Elsevier B.V.
Volume 2, Issue 5, November 2010, Pages 222-228
Jorge A. Velasco | Luis Lopez | Miguel Velásquez | Magali Boutonnet | Saúl M. Cabrera | Sven G. Järås
Gas-to-Liquids (GTL) technology converts natural gas, through Fischer-Tropsch synthesis, into liquid and ultra-clean hydrocarbons such as light oils, kerosene, naphtha, diesel, and wax. Bolivia has natural gas reserves that reach 48.7 trillion cubic feet and produces nearly 40.0 million cubic meters per day, from which, around 88% are exported to Brazil and Argentina. In spite of these considerable amounts of natural gas reserves and production, the country experiences a shortage of diesel which cannot be solved using conventional refining processes due the light nature of its crude oil. Thus, the GTL process seems to be a promising solution for Bolivia's diesel problems, at the same time that its natural gas reserves could be monetized. Although GTL can be considered as a well proven and developed technology, there are several aspects along the main processing steps (synthesis gas generation, Fischer-Tropsch synthesis, and product upgrading) to be considered at the time of implementing a GTL plant. The aim of this paper is to give an overall view of some relevant issues related to Gas-to-Liquids technology as an option for natural gas industrialization in Bolivia, and also to provide a landscape of Bolivian natural gas industry. © 2010.
Volume 3, Issue 2, May 2011, Pages 402-412
Ruud Weijermars | Guy G. Drijkoningen | Timo J. Heimovaara | E. Susanne J Rudolph | Gert Jan Weltje | Karl Heinz A A Wolf
The clean energy transition and EU 2020 targets require a further shift from coal and oil toward natural gas. As a relatively clean fossil fuel, gas must bridge the transition period required for renewable energy technologies to mature such that larger energy quantities can be economically produced to meet demand. Until then, gas is required in Europe and energy scenarios suggest natural gas consumption will reach 650 bcma in 2020 and 780 bcma in 2030. However, conventional gas production in the EU will decline to 230 bcma in 2020 and 140 bcma in 2030. This means the dependency on intercontinental LNG and pipeline imports will increase further and - by 2030 - must account for up to 80% of total gas supply. Consequently, the development of European unconventional gas resources could reduce the required gas imports and would improve security of supply - and also reduces the risk of price shock. This paper outlines the imminent decline of Europe's conventional gas production, highlights the potential of unconventional gas resources and advocates the key role of R&D to improve the performance of unconventional gas projects. Delft University of Technology has launched the Unconventional Gas Research Initiative (UGRI). The research framework, vision, aims and targets are outlined in this report. © 2011 Elsevier B.V.
Volume 2, Issues 2-3, July 2010, Pages 105-113
| Zhongxi Chao | Hugo Atle Jakobsen
Hydrogen production by the Sorption Enhanced Steam Methane Reforming (SE-SMR) process was studied with a numerical two-fluid model. The process was simulated in a three dimensional bubbling fluidized bed reactor. The effects of pressure, steam-to-carbon ratio and inlet gas flow rate on the reactions are studied. High pressure and low steam-to-carbon ratio will decrease the conversion of methane. But the high pressure makes the adsorption of CO2 faster. Compared to the standard SMR process, the methane conversion and heat utility are enhanced by CO2 adsorption. The CO2 produced in the methane reforming process is adsorbed almost totally in a relative long period of time in the bubbling fluidized bed. It means that the adsorption rate of CO2 is fast enough compared with the SMR rate. In a certain range of gas flow rates, the mass transfer and reaction kinetics can reach the equilibrium, and the reaction efficiency is independent of gas flow rate. The temperature distribution is almost uniform over the whole reactor. © 2010 Elsevier Ltd.
Volume 8, Issue , September 2012, Pages 68-84
Roger M. Slatt | Norelis D. Rodriguez
Comparison of some Paleozoic and Mesozoic gas shales has revealed a generally common sequence stratigraphy, consisting of, from the base upward: combined sequence boundary/transgressive surface of erosion (SB/TSE) upon which sits a transgressive systems tract (TST) enriched in organic matter, then a somewhat 'cleaner gamma-ray' highstand or regressive systems tract (HST/RST). When resolvable, this stratigraphy occurs at 2nd, 3rd, and 4th order relative sea level cyclicity, forming couplets of relatively organic-rich (TST and condensed section-CS) and organic-poor (HST/RST) strata at these time scales. A higher order sequence stratigraphy can be developed for Mesozoic shales than for Paleozoic shales owing to greater biostratigraphic age resolution of the former. The higher frequency cycles are superimposed upon lower frequency cycles, giving rise to a complex stratigraphy of several couplets of differing thickness and distribution. These documented common characteristics provide the basis for a unifying, general sequence stratigraphic model for shales which can be utilized to identify, predict and map the most productive facies within a shale stratigraphic interval.There also are several commonalities in geochemistry of gas shales. Prolific gas shales are usually >200 ft (65 m) thick, contain >3% TOC, have Hydrogen Index values >350 mg HC/g, contain Type II kerogen and have organic maturity values >1.1% Ro. Organic-rich shales typically contain minerals such as pyrite and phosphates (apatite) and show biomarker ratios (pristane/phytane, steranes distribution, C 13-C 20 regular isoprenoids and C 18 aryl isoprenoids) indicative of anoxic conditions during source rock deposition. In high maturity areas, there is a reversal in ethane isotope abundance owing to secondary cracking of hydrocarbons; such a reversal is normally associated with best gas production. Relative hydrocarbon potential (S1 + S2/TOC) is a geochemical parameter which reflects oxygenation conditions in the depositional environment. It can be related to relative sea level fluctuations within a sequence stratigraphic context.Understanding the sequence stratigraphy of shale provides a powerful tool not only for regional-to-local stratigraphic correlations from well logs and seismic reflection records, but also for high-grading stratigraphic intervals most favorable for preservation of organic matter and gas generation and storage. © 2012 Elsevier B.V.
Volume 3, Issue 1, March 2011, Pages 334-340
Mahmood Farzaneh-Gord | Mahdi Deymi-Dashtebayaz | Hamid Reza Rahbari
At CNG filling station, compressed natural gas must be stored in storage system in order to make the utilization of the station more efficient. There are two systems for storing natural gas namely buffer and cascade storage systems. In buffer storage, CNG is stored at single high-pressure reservoirs. The cascade storage system is usually divided into three reservoirs, generally termed low, medium and high-pressure reservoirs. In current study, based on first and second laws of thermodynamics, conversation of mass and real gas assumptions, a theoretical analysis has been developed to study effects of reservation type on performance of CNG filling stations and filling process. Considering the same final natural gas vehicle cylinder (NGV) on-board in-cylinder pressure for both storage systems, the results show that each storage type has advantages over the other. The best configuration should be selected by balancing these advantages. © 2011 Elsevier B.V.
Volume 15, Issue , November 2013, Pages 82-92
Afshin Tatar | Amin Shokrollahi | Mohammad Mesbah | Saeed M Mamun Ar Rashid | Milad Arabloo Arabloo | Alireza Bahadori
Gas injection process is one of the most dependable techniques in enhanced oil recovery (EOR) methods. Multiple contact miscible injection is the method that has been well-established during last decades. Due to high sensitivity of local sweep efficiency to minimum miscibility pressure (MMP), this parameter has a key role in the gas injection process designing. Conventional tests to determine gas-oil MMP such as rising bubble apparatus and slim tube displacement are either costly or time consuming. Thus, it is necessary to utilize a quick, not expensive, and reliable method to determine MMP. In spite of several studies and various attempts to develop a model to predict MMP satisfactorily, there is no reliable and comprehensive MMP prediction model for CO2. Inductive machine learning algorithms have already been applied in various branches of science and engineering in an attempt to model several macroscopic properties through pattern recognition and generalization of results using a set of experimentally measured data. The objective of this study is to develop a comprehensive and intelligent model based on the radial basis neural network to predict of MMP for pure and impure CO2. To construct and evaluate the proposed model, about 147 data sets from literature and corresponding gas/oil compositional information were used. The results show the superiority of the proposed model in comparison with existing methods and predicted values are in good agreement with the experimental data. The other feature of the proposed model is its generalization capability. The proposed model provides accurate values for data sets that have not been introduced to the network previously. At the end, the outlier diagnosis is performed to determine the data sets that might be different from the bulk of the data present in the dataset. © 2013 Elsevier B.V.
Volume 4, Issue , January 2012, Pages 8-16
Georgios Karavalakis | Thomas D. Durbin | Mark Villela | Joseph Wayne Miller
Interest is growing in the expanded use of natural gas as an alternative to conventional liquid fuels for use in automotive internal combustion engines. This study investigates the implications of natural gas composition on the gaseous pollutants, fuel economy, and the engine power output of two light-duty vehicles (a 2002 Ford Crown Victoria and a 2006 Honda Civic GX) operated over different driving cycles. The results of the study show that for modern light-duty NGVs, fuel properties have a clear and direct impact on fuel economy and some emissions components, such as CO 2 and NMHC, but not for other emission components, such as THC, NO x, and CO. The gases with the higher energy contents provided better fuel economy on a volumetric basis and some higher power levels. Changes in CO 2 depended on the fuel/cycle/vehicle, but, generally, blends with heavier hydrocarbons and lower H/C ratios, had higher CO 2 emissions. NMHC emissions were very low, in general, but did increase for the two fuels with the highest levels of heavier hydrocarbons for both vehicles. THC emissions showed higher emissions for the fuel with the higher levels of methane for the Crown Victoria, but no trends for the Honda. CO emissions were higher for the two fuels with the highest Wobbe numbers for the Honda under some test conditions, including the cold-start phases of the driving cycles, but did not show significant fuel differences for the Crown Victoria. Changing fuel composition impacted NO x emissions showed only limited fuel effects for the two vehicles. © 2011 Elsevier B.V.
Volume 15, Issue , November 2013, Pages 69-75
Mohammad Mahdi Ghiasi | Alireza Bahadori | Sohrab Zendehboudi | Ahmad Jamili | Sina Rezaei-Gomari
In economic and safety hazards points of view, it is crucial to avoid the formation of clathrate hydrate of gases in oil and natural gas transportation/production systems. Injection of methanol as a thermodynamic inhibitor is a common approach in industry to shift the hydrate phase boundary to higher pressures/lower temperatures. Accurate computation of methanol loss to the vapor phase within hydrate inhibition is essential to calculate the right injection rate of methanol. In this study, two procedures have been proposed for fast and precise estimating the ratio of methanol content of vapor phase to methanol liquid composition (RMeOH). In the first method, a new mathematical expression is presented. The obtained correlation is reliable for temperatures between 267.15 and 279.15K and pressures between 1160 and 28000kPa. The second method employs artificial neural network (ANN) approach for RMeOH prediction. Both developed models results are in good agreement with reported data in literature. The ANN based model, however, is more accurate than the new correlation. © 2013 Elsevier B.V.
Volume 11, Issue , March 2013, Pages 7-11
Vangala Dhanunjana Chari | Deepala V S G K Sharma | Pinnelli Syam R Prasad | Sarabu Ramana Murthy
Methane gas hydrate (MH) formation/dissociation were investigated in nano silica and water system in a non-stirred reactor. The MH yield was significantly improved in the presence of nano silica. The overall methane hydrate conversion (≥80%) was achieved by optimizing the nano silica to water ratio. Two-stage dissociation was observed after a rapid de-pressurization. Methane gas intake of this system was steady for multiple freezing-thawing cycles signifying improved stability for methane gas storage. © 2012 Elsevier B.V.
Volume 2, Issues 2-3, July 2010, Pages 61-68
Ali Nakhaei Pour | Mohammad Reza Housaindokht | Sayyed Faramarz Tayyari | Jamshid Zarkesh | Mohammad Reza Alaei
The kinetic of the Fischer-Tropsch synthesis (FTS) over nano-structured iron catalyst promoted with Mg, La and Ca, was studied in a continuous spinning basket reactor. Fe/Cu/Si nano-structured catalyst was prepared by co-precipitation in a water-in-oil microemulsion. The results indicated that both the rate constant (k) and the adsorption parameter (b) in a common two-parameter Fischer-Tropsch rate expression decreased with increasing the catalyst surface basicity. Since decreases in rate constant (k) and the adsorption parameter (b) affected the FTS rate in reverse direction, the basicity of catalyst surface showed complicated effects on kinetic parameters of FTS reaction. The optimum promoter would be one that its rate constant (k) should not be too low and its adsorption parameter (b) should not be too high. © 2010 Elsevier B.V.
Volume 2, Issues 2-3, July 2010, Pages 86-104
The aim of any value chain & network analysis is to understand the systemic factors and conditions through which a value framework and its firms can achieve higher levels of performance. The upstream oil & gas business is increasingly stimulated for growth by federal legislation (e.g. tax credits unconventional gas plays), while the corporate earnings in the US midstream and downstream energy segments remain strictly regulated and constrained by FERC and state regulators. This study concisely describes the physical and the financial value chains of the US natural gas business in a systemic fashion. The value chains of the natural gas industry are governed and interconnected by a regulatory decision-making framework. Legislation and regulation by the US Congress for the upstream energy value chain traditionally aim to facilitate the development of domestic natural gas fields. Likewise, FERC regulation maximizes access to the midstream gas transmission segment and provisions for fair tariffs for all shippers. State regulators protect the end-consumers in the downstream value chain by providing guidelines and rulings in rate cases. Corporate energy development decisions are critically impacted by such energy policies and regulations. Long-term, mid-term and short-term measures are distinguished based upon the duration of their impact on the performance of the US natural gas market. The present analysis of the physical and financial value chains and the regulatory framework that governs the US natural gas market provides new insights on appropriate policies and regulatory strategies that could improve both the liquidity and security of supply in the European gas market. Strategic and tactical instruments for maximizing returns on investment for regulated energy utilities are also formulated. © 2010 Elsevier B.V.
Volume 9, Issue , November 2012, Pages 16-27
David A. Wood
The evolution of global and regional LNG trade over the past twenty years has been a story of rapid growth, diversification and increased flexibility in LNG cargo movements. Asia continues to dominate global LNG trade, but the European LNG market has evolved significantly in the past decade and seems destined for sustained growth and diversification over the next decade or so. Despite the LNG import market in North America being overwhelmed by unconventional gas developments in the past few years, future sustained growth of LNG demand in Asia and Europe are underpinned by firm new project commitments. A number of North American LNG export projects are progressing with a view to supplying this growing market demand in Europe and Asia. New gas discoveries in deepwater offshore East Africa and Eastern Mediterranean are also likely to compete for LNG market share in growing European and Asian gas markets Country and regional statistics presented illustrate how significantly the global LNG industry has changed in the past decade. These statistics reveal the complexity of commercial, political and technical drivers at play, particularly in the case of Europe, and how these drivers are conspiring to boost future demand for LNG. © 2012 Elsevier B.V.
Volume 8, Issue , September 2012, Pages 121-131
Prob Thararoop | Zuleima T. Karpyn | Turgay Ertekin
Most existing coalbed methane (CBM) simulators usually treat coal seams as dual-porosity, single-permeability systems ignoring the effects of water presence in the coal matrix. In this study, a compositional dual-porosity, dual-permeability CBM simulator has been developed. The CBM reservoir is treated as a dual-porosity, dual-permeability system consisting of coal matrix and fracture network. The development of the proposed numerical model incorporates the effects of water presence in the coal matrix and the phenomena of coal shrinkage and swelling. The transport of gas follows a multi-mechanistic flow mechanism triggered by pressure and concentration gradients. In addition, the proposed simulator is able to collapse to simpler coal seam representations and was successfully tested against the existing commercial and research CBM simulators for CO 2-enhanced CBM recovery process. Successful history matching exercises were performed on pure CO 2 injection and flue gas injection tests using the actual field data. © 2012 Elsevier B.V..
Volume 4, Issue , January 2012, Pages 29-34
Hui Zhang | Hongyun Zhang | Boyun Guo | Minghui Gang
Underbalanced drilling (UBD) has been proven to be an effective means of increasing drilling performance and minimizing formation damage. While UBD with gases (air, nitrogen, natural gas, etc.) gives the highest rate of penetration (ROP), addition of liquid phase significantly reduces ROP. The objective of this study was to understand the mechanism of rock failure that controls the ROP and use the gained knowledge to optimize gas UBD design. An analytical model was developed in this study to calculate the near-wellbore rock stresses induced by the bottom hole pressure and temperature. A numerical model with finite element method was used to verify the results from the analytical model. Both of the analytical model and the numerical model reveal that the rock stress in the bottom hole rock can change from compressive stress in over-balanced conditions to tensile stress in underbalanced conditions, depending on the bottom hole pressure. A new finding from this study is that the temperature-induced stresses in the bottom hole rock can contribute significantly to the stress unbalance and cause rock failure. This paper provides drilling engineers insight and understanding of rock failure mechanics, which are useful for designing bottom hole pressure and gas injection rate to improve UBD performance. © 2011.