• Thermodynamic Model for Prediction of Phase Equilibria of Gas[taliem.ir]

    Thermodynamic Model for Prediction of Phase Equilibria of Gas Hydrates in the Presence of Water-Insoluble Organic Compounds


    A thermodynamic model for predicting pressure – temperature phase diagrams of structure II and structure H clathrate hydrates of methane, carbon dioxide, or hydrogen sulfide in the presense of “water-insoluble” organic componds is presented. The model is based on equality of  water fugacity in the aqueous and hydrate phases. The solid solution theory of van der Waals – Platteeuw (vdW-P) is used for calculating the  fugacity of water in the hydrate phase. The PengRobinson (PR) equation of state (EoS) is employed to calculate the fugacity of the  compounds in gas phase. It is assumed that the gas phase is water and promoter free and the organic compounds do not have considerable  effects on water activity in liquid phase. The results of this model are finally compared to existing experimental data from the literature.  Acceptable agreement is found between the model predictions and the investigated experimental data

  • Processes and apparatuses for formation, separation and[taliem.ir]

    Processes and apparatuses for formation, separation and pelletizing of gas hydrate


    Despite the suggested applications for gas hydrate in transportation and storage of natural gas, desalination of water, etc., there has been no  applied industrial application for it. There are several patents and papers on thermodynamically and kinetically promotion of gas hydrate  formation and many concerning its related processes. In designing a process based on gas hydrate application in industry, one must include the following operations: formation, separation, pelletizing, storage, transportation and gasification. In this review, operations of each gas  hydrate’s application are studied and processes for formation, separation and pelletizing of gas hydrate are widely discussed. Gas hydrates  formation systems are classified based on contact type of gas and liquid. Autoclave, spray, bubble column, using micro bubbles, hydrate  formation with emphasis on nucleation sites and gas ice process are discussed as hydrate formation systems. Separation of gas hydrate and  unreacted water is a solid-liquid separation process which is done by operations based on density difference (using gravity force or centrifugal  force) or mechanical separation such as filtration. Pelletizing of gas hydrate with more storage gas capacity and less decomposing rate has  been accomplished by piston and cylinder or roller systems

  • Quantification of Uncertainties Associated with Gas Production[taliem.ir]

    Quantification of Uncertainties Associated with Gas Production from Gas Hydrates in the Makran Offshore Area of Iran


    Recent seismic surveys detected thick layer of free gas underlying hydrate bearing sediments through observation of direct seismic attributes,  in the area of 27,000 km2, in the Makran offshore area of Iran. This potential energy source should be evaluated concerning production potential which is subject to very large uncertainties. Whereas, a meaningful development plan incorporating the associated uncertainty calls for large number of simulation runs, analytical models are useful tools for fast engineering calculations conducted at the  beginning of the life of reservoirs. In this paper, we investigate the class in which gas hydrates on the continental slope off Iran belong, as well as we propose the best production strategy which is well suited to the conditions of gas hydrates within the study area to maximize production. Then, we use Gerami and PooladiDarvish’s analytical model along with Monte Carlo simulation to capture the effect of uncertainty in hydrate and reservoir parameters on the performance of a prospect, located on the continental slope off Iran. The importance of employing analytical models for quantification of uncertainty, especially in the initial stages of development of gas hydrate reservoirs; also, is  discussed. The results of study indicate considerable contribution of hydrates in total produced gas, as well as high hydrate recovery. It reveals a significant economic advantage which guarantees gas production from gas hydrates in the Iranian part of the Oman Sea using conventional technology

  • Prediction of Gas Hydrate Dissociation Point by Using Different[taliem.ir]

    Prediction of Gas Hydrate Dissociation Point by Using Different Equations of State and Mixing Rules in binary systems


    In this work, the ability of different equation of states and mixing rules for prediction of hydrate formation pressure, are compared. For this  urpose, by using Van der Waals–Plauteeuw model for solid hydrate phase and six equation of states for calculation of fugacity of components in  as and liquid phases, the pressure of hydrate formation in different mixtures have been calculated by three different mixing rules Van der Waals,  anesh and GNQ, then by comparison of calculated results with experimental data, determined the accuracy of mixing rules and EOSs. Studied  ystems contain binary mixtures CH4, C2H6, C3H8, i-C4H10, N2, CO2, and H2S with water in hydrate forming conditions. The interaction parameters in each mixture have been optimized by using two phase equilibrium data and then the optimized parameters have been used for three phase equilibrium calculations. Comparison of the calculated pressure of hydrate forming with experimental pressure shows that for most of binary mixtures in studied temperature and pressure ranges, GNQ mixing rule with average percent of error 7% has more accuracy than three other mixing rules Van der Waals and Danesh, and among of EOSs, SRK equation of state is better than others and using from YU-LU equation of state be not suggested

  • Phase Equilibria of Hydrates of Furan, Acetone, 1,4-dioxane,[taliem.ir]

    Phase Equilibria of Hydrates of Furan, Acetone, 1,4-dioxane, Tetra n-Butyl Ammonium Chloride and Tetra n-Butyl Ammonium Floride


    In this communication, we first report experimental hydrate dissociation pressures for the methane/ carbon dioxide + furan/ acetone/ 1,4- dioxane + water and the methane + tetra n-butyl ammonium chloride (TBAC) + water as well as the methane /carbon dioxide + tetra n-butyl ammonium floride (TBAF) + water systems in the temperature ranges of (269.9 to 303.3) K. An isochoric pressure-search method was used to generate the experimental data. The hydrate dissociation data are compared with the corresponding literature data and the predictions of a  previously reported thermodynamic model and acceptable agreement is observed

  • Characterization and Identification of Gas Hydrate Bearing[taliem.ir]

    Characterization and Identification of Gas Hydrate Bearing Sediments of Oman Sea Using Seismic Methods


    Gas hydrates attracted worldwide attention due to their potential as huge energy resource in the recent decades. Therefore identifying and prospecting them is essential for strategic hydrocarbon reservoir management. Seismic methods are known as a powerful gas hydrate exploration methodology. In this research pre-stack seismic attributes have been used to identify elastic properties and qualitative hydrate  saturation of sediments. Using AVO analysis on pre-stack seismic data, occurrence of gas hydrate has been confirmed in the Oman Sea. Also  post-stack seismic meta-attributes (applying pattern recognition and classification methods on several attribute planes) have been successfully used to make separation between hydrate and non-hydrate sediments. Joint use of pre- and post-stack seismic attributes will be a good evaluation techniques for confirmation of this study.

  • The Effective Parameters of Hydrate Formation in the Presence of Porous Media[taliem.ir]

    The Effective Parameters of Hydrate Formation in the Presence of Porous Media


    Generally, the interest on the utilization of porous media in hydrate formation is mainly due to its natural occurrence in the ocean depths. The  hydrate formation is potentially influenced by temperature, pressure, salinity, gas composition and interfacial surface area which can be  affected by the presence of porous media. The effects of different types of porous media such as silica, activated carbon, carbon nanotube  and silica gel on hydrate formation are considerable depending on the specific area, pore volume and pore size distribution. The presence of  porous media in methane hydrate formation could affect the rate of hydrate formation and the amount of gas encaged in the hydrate phase. The mentioned parameters are important in selective gas separation utilizing hydrate technology. In this study, the effect of the presence of  porous media on hydrate formation technology was investigated. The aim was to provide a guide to future development in selecting suitable  porous media in hydrate formation for gas purification and gas storage as an energy saving method

  • Determination of Structure and Formation Conditions of Gas[taliem.ir]

    Determination of Structure and Formation Conditions of Gas Hydrate by Using TPD Method and Flash Calculations


    In this work, satbility calculations and determination of gas hydrate structure in equilibrium conditions by using minimization of TPD function for  ethane-water system (SI), propane-water system (SII) and methane-methyl cyclo pentane-water system (SH) were performed. Based on results, at 274 K and 275 K temperatures, the liquid phase of methane-water system at 27 bar and 30 bar pressures, propane-water system at  .7 bar and 2.5 bar pressures and methane-methyl cyclo pentane-water system at 9.6 bar and 10.1 bar pressures was decomposed. As a result  of decomposition of liquid phase for these systems, two new phases, a new liquid phase and hydrate phase were formed. Subsequently,  multiphase flash calculations in order to determine the amount and composition of stable phases in equilibrium state were performed. For minimization of TPD function, Algorithm Genetic was used. The results Show good accuracy with data of Heriot Watt university hydrate model   (HWHYD)

  • Hydrate-Related Drilling Hazards and Their Remedies[taliem.ir]

    Hydrate-Related Drilling Hazards and Their Remedies


    Considerable fuel resource for the future, Transportation ease of gas hydrate (as natural gas phase state), likely role in global climate change  and potential drilling hazards are the main reasons for researcher’s attraction to gas hydrate issues. The gas hydrates have been recognized  as significant potential resources for the 21st century fuel. However, from the drilling perspective, the gas hydrates seem as dangerous drilling  azards. Because of the importance of drilling operation as the first attempt to access energy sources, it is necessary to pay more attention to these hazards. The main objective of this article is to present a comprehensive review about the drilling problems related to  hydrate formation in drilling operations and remedies of problems for understanding the problem in petroleum industry. Some of the notable  problems, explained in this article, include wellbore stability, plugging chokes, kill lines, BOP, gas cut mud and sea floor stability. Different  methods for the gas hydrate suppression during drilling operations and removing blockage practices are perused in this article

  • Assessment of Nucleation Kinetic Mechanisms in Gas Hydrate[taliem.ir]

    Assessment of Nucleation Kinetic Mechanisms in Gas Hydrate Crystallization Processes


    Nucleation is one of the most important steps in the process of crystallization of gas hydrates. In the present work the nucleation mechanism  of gas hydrate formation process using the propane as a sII gas hydrate former is investigated at isothermal operating conditions. Effects of  variations of supersaturation and impeller speed on the kinetics of hydrate nucleation are also presented. Differente expressions for  dependence of induction time with degree of supersaturation are employed. The accuracy of the predicted induction times for the case of progressive nucleation are always much higher than those obtained through instantaneous nucleation assumption at all ranges of impeller  speeds. It is found that the heterogeneous progressive nucleation is the most probable nucleation mechanism at the early stages of gas  hydrate formation processes

  • Gas hydrate formation inhibition using[taliem.ir]

    Gas hydrate formation inhibition using low dosage hydrate inhibitors


    Development and utilization of Low Dosage Hydrate Inhibitors (LDHI) have been attracted researchers and industry for almost two decades.  These inhibitors are known to be more effective, more environmental friendly, less corrosive and havelower capital and operational expenses. These inhibitors are usually classified to Kinetic Inhibitors (KI) and Anti-Agglomerants (AA). While kinetic inhibitors prevent hydrate formation  by prolonging induction time of hydrate formation more than the residence time of free water in pipeline, anti agglomerants inhibits pipeline  plugging acting as a hydrate emulsifier. Environmental aspects of commercial LDHI’s have encouraged researches to look for more   environmentally friendly LDHI’s. Considerable efforts have been made to develop non-ionic surfactants e.g. Alkylamide or zwitterionic surfactants, which can be effective inhibitors or to utilize environmentally friendly materials like starch or anti-freeze proteins. In present paper,  these research activities, patents and industrial reports are reviewed, including: chemicals with kinetic or anti agglomeration effects, their mechanism of acts, Compatibility, chemical screening and selecting methods like molecular Dynamics simulations, experimental procedures,  data reproductivity, stochasticity, inhibitors synergism, multifunction inhibitors, inhibitors surfactant effects and surface interfacial properties, biodegradability, toxicity and environmental impacts