00497 A study on wellbore stability in fractured rock masses with impact of mud infiltration

00497 A study on wellbore stability in fractured rock masses with impact of mud infiltration

16 Fuel system is not yet finalized and may impact on China’s ability to compete for CDM-projects; the priorities of the Chinese authorities may not m...

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16 Fuel system is not yet finalized and may impact on China’s ability to compete for CDM-projects; the priorities of the Chinese authorities may not match those of foreign investors; the main expertise regarding CDM is found in a few ministries and research institutes in Beijing, and there is a need to increase capacity for CDM among local project developers and authorities; most research carried out concerned technical issues, and there is a need to include economists and market experts in order to increase understanding of the market.

16 FUEL SCIENCE AND TECHNOLOGY Fundamental science,analysis, instrumentation 04/00493 Schwartz,

A mathematical model for an expanding foam W. and Roy, R. V. Journal of Colloid and Interface Science, 2003, 264, (1), 237-249. A theoretical and numerical model is presented for the shape evolution of the thin liquid films separating the gas bubbles in a foam. The motion is due to capillary action, surface tension gradients, and the overall expansion of the foam. The expansion is the result of the increase in gas content with time. Process modelling is accomplished via the solution of three coupled partial differential equations. Two time scales are included in the model: a process time and a drying or curing time. It is demonstrated that the amount of surfactant is the dominant control mechanism for the final film thickness. If sufficient surfactant is present, the films will be shown to dilate uniformly in space. A number of known features of expanding foams are reproduced by the model. L.

04/00494 A mathematical model of thermal performance of a solar air heater with slats Ammari, H. D. Renewable Energy, 2003, 28, (lo), 1597-1615. A mathematical model for computing the thermal performance of a single pass flat-plate solar air collector is presented. Air channels were formed by providing metal slats running along the circulated air passage linking the absorber plate by the bottom one in an endeavour to enhance the thermal efficiency of the solar air collector. A mathematical model, therefore, is developed by which the influence of the addition of the metal slats on the efficiency of the solar collector is studied. A computer code that employs an iterative solution procedure is constructed to solve for the governing energy equations to estimate the mean temperatures of the collector. The effect of volume airflow rate, collector length, and spacing between the absorber and bottom plates on the thermal performance of the present solar air heater was investigated. Furthermore, a numerical comparison of the present design with the most common type of solar air heaters is conducted. The results of the comparison have indicated that better thermal performance was obtained by the modified system. 04/00495 A new buoyancy model replacing the standard oseudo-densitv difference for internal natural convection in bases Sparrow, E. M. and Abraham, J. P. International Journal of Heat and n/lass Transfer, 2003, 46, (19), 3583-3591. Natural convection in enclosed spaces has been analysed and numerically evaluated using a direct buoyancy model that replaces the pseudo-density difference which has been heretofore standard in all previous studies of internal natural convection of gases. It was demonstrated conclusively that the pseudo-density-difference model is totally irrelevant to the physical processes that create the buoyancy. When properly accounted, the presence of the pseudo-density difference does no harm, but it provides a source of confusion for the source of the buoyant forces that create motion. This conclusion was drawn from numerical solutions of three-dimensional natural convection in an oven-like cavity. These solutions were irrefutably supported by experimental data. It was also demonstrated that accounting for the naturally occurring pressure variations within the enclosed space had a negligible effect upon the surface heat transfer coefficients. The commonly used Boussinesq equation of state was found to provide accurate surface heat transfer results provided that the density, thermal conductivity, viscosity, and coefficient of thermal expansion are evaluated at a temperature that is the average of the temperatures of the surfaces which bound the enclosed space.

science

and technology

(fundamental

science,

analysis,

instrumentation)

04/00496 A study on regeneration of Mn-Fe-Zn-0 supported upon -A1203 sorbents for hot gas desulfurization Zhang, J. et al. Fuel Processing Technology, 2003, 84, (I-3). 217-227. In this study, the regeneration conditions of Mn-Fe-Zn-0 supported upon -Al203 sorbents for high-temperature desulfurization of fuel gases were investigated. Mn-Fe-Zni -Al203 sorbents with Mn/Fe/Zn molar ratio of 2:1:0.2, AMFZ0.2, were prepared. Desulfurization and regeneration were carried out in a quartz fixed-bed reactor of lo-mm diameter. Sulfidation tests were performed at 650°C using the gas mixture containing (mol) 0.3%H+ll.62%H~-l9.34%CO-6.85%CO~61.84%Nl at SV = 3000 h-‘. Sulfur capacity of the fresh sorbent was about 5.3 gS/lOO g Sorbent. Regeneration parameters including temperature, concentration of oxygen, space velocity and steam content have been considered in order to obtain suitable regeneration conditions. The regeneration was performed at the following parameters-pressure: atmosphere, temperature: 600-75O”C, space velocity: 2000-3000 h-’ and gas composition (vol.%): 2-8 02, 4-10 Hz0 with Nz balance. Typical properties of the sorbents before and after regeneration were characterized using XRD, SEM, BET and ICP methods. The most suitable regeneration conditions were obtained including 700°C of regeneration temperature, 6.0% of oxygen content and 8.0% of steam in the gas stream.

04/00497 A study masses with impact Chen, X. et al. Journal (3%4),

on wellbore stability of mud infiltration of Petroleum

Science

in fractured and Engineering,

rock 2003,

38,

145-154.

Maintaining a stable borehole is one of the major tasks encountered in the oil and gas industry due to the fact that wellbore instability-related problems will result in additional high drilling costs and have a severe impact on drilling schedule. Wellbore stability analysis has therefore been included at the well planning stage of many operating companies. However, majority of such wellbore stability analyses are based on continuum mechanics. Factors contributing to wellbore instability, such as trajectory of the wellbore, orientation and magnitude of the in situ stress field, rock properties, in situ and induced pore pressures and mud pressure, are normally considered in the analyses. In addition to failure in intact rock, wellbore instability can also be initiated along natural discontinuities, such as bedding planes and fractures, in rock masses. Furthermore, the rock masses will become more prone to wellbore instability along fractures penetrated by mud filtrate due to reduction in the fracture friction angle and loosening of blocks. In this paper, coupled numerical analyses are presented to investigate the influence of fractures in rock masses, in particular mud infiltration into the fractures, on wellbore stability under both isotropic and anisotropic stress states. Two regular fracture geometries are considered in the analyses. A simplified approach is developed to take into account the friction angle reduction of the fractures that occurs when infiltrated with mud. The results show that the presence of natural fractures and friction angle reduction of fractures due to mud infiltration significantly affect wellbore stability during drilling. 04/00498 An application of exploratory data analysis (EDA) as a robust non-parametric technique for geochemical mapping in a semi-arid climate Bounessah, M. and Atkin, B. P. Applied Geochemistry, 2003, 18; (8): 1185-l 195. Exploratory data analysis (EDA) techniques based on the boxplot and robust-class selection were applied to the analysis of single-element stream sediment data in the Co110 area (north-east Algeria). The area is characterized by many factors that affect data variability: variation of lithology, combined existence of permanent and ephemeral streams, flash floods, rugged terrain, and climate. The boxplot proved to be very useful in capturing the empirical data distribution, the skewness, and in defining outliers. No data transformation was needed prior to the analysis of single element distributions (Cr, Pb, Zn, Cu, As, and Fe) as is the case in classical statistics. Geochemical mapping of these elements was based on resistant class selection as defined by the boxplot. Results showed the close spatial correlation of outlier data for Cr with a plagioclase-lherzolite intrusion and known chromite pods. The geochemical maps of Pb, Zn, Cu and As concentrations showed an association of these elements coincident with known base-metal sulfides and arsenopyrite mineralization, delineating a northeastern anomaly spreading well over known mineralization. The choice of the robust classes based on the boxplot also showed the close spatial distribution of Fe with known hematite and magnetite mineralization. EDA techniques proved to be very useful in delineating known mineralization in the Co110 area where stream sediment data is subject to variability owing to many factors (geologic, physiographic and climatic). EDA proved to be a simple and very useful tool in analysing single-element geochemical data. EDA could be used in similar terrains as an alternative to the classical methods where a normality precondition is needed prior to analysis and where class selection may be affected by the presence of ‘wild’ data. Fuel

and

Energy

Abstracts

January

20