المستودع الرقمي لـكلية الهندسة

Abstract

The accurate detection and confirmation of formation pore pressure and fracture gradient has become almost essential to the drilling of deep wells with higher than normal pore pressure. Generally, the formation pressure is the presence of the fluids “oil, gas or salt water” in the pore spaces of the rock matrix. Therefore, the fluid confined in the pores of the formation rock occur under certain degree of pressure, generally called formation pore pressure. Formation pore pressure is defined as the pressure acting on the fluids in the pore space of the rock, which is equal to the difference between the total overburden stress and grain to grain stress. Normal formation pressure is equal to the hydrostatic head of the native formation fluid or water exerting from the top of water table to the subsurface formation depth. Hydrostatic pressure is the pressure in a column of salt water or usually defined as the pressure exerted by a column of fluid, the pressure is a function of the average fluid density and the vertical height or depth of the fluid column. In most cases, the fluid vary from fresh water with a density of (8.33 Ib/gal) (0.433 psi/ft) to salt water with a density of (9 Ib/gal) (0.465 psi/ft). Consequently the hydrostatic pressure gradient of such system will be greater in terms of (psi/ft) than that of a fresh water system and will be displayed on pressure depth plot by pressure gradient line whose slope is greater than that of fresh water hydrostatic pressure. Indeed, formation pore pressure depending on the magnitude of the pore pressure, it can be described as being either normal, abnormal or subnormal. Whereas defined as follows, we had defined normal pore pressure which is equal to the hydrostatic pressure, abnormal pore pressure is defined as any pore pressure that is greater than the hydrostatic pressure of the formation water occupying the pore space, and sometimes called overpressure or geopressure. Subnormal pore pressure is defined as any formation pressure that is less than the corresponding fluid hydrostatic pressure at a given depth. The objectives of this study are:To determine the origin, nature, causes and the location of the subnormal and overpressued formations in part of Sirte basin area. To determine a graphical correlation relating formation pore pressure and fracture gradients to depth for selected areas extending fromfurther east to North West in the basin.This study is determining the pore pressure and fracture gradient, for selected fields from eastern, central and western Sirte basin, using existing correlations which utilize log and drilling data measured for the selected wells in these areas. The casing setting depths as well as the maximum and the minimum mud weight gradients to be used for future drilling activities in these selected areas in Sirte basin have been determined. The location and the magnitude of the lost circulation zones as well as the overpressured zones have been determined and correlated with depth depending on the location of the studied area in the basin. It was found that the lost circulation zones are located at depths of approximately in the range 3000 to 6000 ft from east toward west. It is concluded that the calculated pore pressure and the fracture gradients values obtained from the log data are in good agreement with the values obtained form the drilling data. It is concluded that the results obtained in this study for the eastern part of Sirte basin was satisfactory and can be used with good confident for future drilling activities in the area, where the obtained results for either the central or the western parts of the basin are not enough to draw final conclusions for future mud design programs in these areas. It is therefore recommended that further investigation and extensive study should be conducted for these two areas by gathering enough log and drilling data from different fields in these area which was not available during this study.
احمد خليفة رمضان طنيش (2009)

Abstract

The aim of this study is to assess the wind energy potential and to compare Weibull and the Maximum Entropy Principle (MEP) distributions, with meteorological measured data. Dernah is selected site, which has good wind characteristics (seasonal, monthly and diurnal wind speed variations and wind direction variations), for possible wind energy applications. The data source is measured at an elevation of 40 m above the ground level for one year period (2003), and it is analyzed statistically. The functions of probability density and power density are calculated using the Weibull and MEP distributions. The Lagrangian multipliers of MEP distribution are estimated numerically at r values of 0 to 5 by using Newton Raphson, Simpson’s rule and Romberg’s methods. The MATLAB simulation is also applied for estimating Lagrangian multipliers. The verification of the results is also assessed by Maple software. The statistical analysis parameters based on wind speed and power density are used as the suitable judgment criterion for the distribution functions. It is found that for MEP distribution, the wind power (W/m2) 450, 395 and 407, are for the cold season, the hot season and for the year 2003, respectively. However, there is no significant difference of the presented peak values of the results in this study for Weibull and MEP distributions. Such result can be attributed to the fact that the average wind speeds were relatively high and the calm spells are about 7% in the year 2003 data.
جبريل يوسف الفيتوري (2010)

Abstract

The conflict that took place in Libya in 2011, up to the present moment, has greatly affected the electrical power network and resulted in the rise of the voltage instability problem. This was due to loss of the some major transmission lines and certain generation units. Owing to the fact that the southern region of the Libyan network has no generation units, voltage drop phenomena has become a common problem as a result of the long transmission distance, which is approximately 750km. A proposed solution in order to solve this problem is via the utilization of small mobile generation units at the network weak points. This thesis revolves around discussing the voltage instability problem within the Libyan Network and how it can be enhanced when small and mobile generation units are connected to the network weak points. It will also establish and identify where the most weakened buses and regions are so that the mobile units should be connected for the attainment of optimized solution. Moreover, this solution was proposed as it can solve not only the voltage instability problem, but it will also solve the inadequacy in generation issue by circulating additional power within the network. Hence, reduce the load shedding phenomena. Furthermore, the thesis also includes future recommendations to improve and enhance the Libyan network by the addition of new 220kV and 400kV transmission lines that will enable the network to cope with the load growth in the future
ربيع محمد عمر (2014)

Abstract

The contribution of this thesis is to improve the understanding of acoustic dynamics in the audio duct with Helmholtz Resonator (HR). In this project, detail measurements of acoustic in a duct with HR induced loud–speaker at various frequencies have been carried out experimentally. Two-microphone technique have been used to measure the net acoustic power transmission in the duct downstream of HR along with the net acoustic power transmission in the duct without the HR. The acoustic wave signals are traveling in the duct as a plane wave, these waves are generated by a signal generator system with a know wave (sine wave). One of the microphone is located just before the neck–duct interface and the other microphone after the HR in the duct. Five type of necks ( perforated neck length 15cm, perforated neck length 10cm, cone–shape neck, Non- perforated neck length 15cm, Non-perforated neck length 10cm ) and three different material of the bottom wall of the cavity ( Teflon, water and cotton ) have been studied. The best results has a good advantage that by using (perforated neck length 15 cm and 4cm diameter because that reduction of noise has been reached 64% percentage and that value is the highest reduction from all experimenting.
إبراهيم فاضل عبد الحميد الزوي (2010)

Abstract

The contribution of this thesis is to improve the understanding of acoustic dynamics in the audio duct with HQ (Herschel-Quincke tube) is essentially a hollow side-tube that travels along a main-duct axis and attaches to the main-duct at each of the two ends of the tube. In this project the detailed measurements of acoustic in a duct with HQ induced by a loudspeaker at various frequencies have been carried out experimentally. Two microphones have been used to measure the net acoustic power transmission in the duct downstream of HQ and compared with the net acoustic power transmission in the duct without the HQ. Two types of HQ and three different ducts have been studied. The acoustic wave signals are traveling in the duct as a plane wave these waves are generated by a signal generating system with a known sinusoidal wave (sine wave). One of the microphones is located just before the HQ-duct interface and the other microphone after the HQ in the duct. Labview software is used to analyze the signals with a sampling rate of 44100s/sam and number of samples is 20000. This study makes an exhaustive understanding of power spectrum of two acoustic channels in the duct with and without HQ. The results show that there is a great potential for HQ tube system to attenuate the noise over conical and cylindrical sections. The sound attenuation on conical section with short HQ shows about 70% and that of cylindrical section a meager 47% at higher frequency. Further more the sound attenuation of cylindrical section with long HQ is occurred at low frequencies.
رضوان نجمي الكوني الشريف (2010)

Abstract

The dynamic model of the heat process trainer PT326 is obtained experimentally by using the Ziegler–Nichols approximation and the system identification MATLAB toolbox. The interfacing data acquisition card is developed in two different designs the first design by using analog to digital, digital to analog IC's (ADC and DAC) and the parallel port, and the other design by using microcontroller and serial port. These two designs were tested in the department and give good results. The velocity PID controller is implemented through the developed cards in real time control system. An adapted neural network algorithm using the backpropagation approximation is tested on real time in the heat process trainer PT326. This research gives a good background for any control and computer engineer in the area of data acquisition and real time control system. The simulation results are the same as the online results of the real time Heat process control system.
نوري احمد عقاب (2010)

Abstract

The new trend of development in Libya is building a more high rise buildings (tall buildings) in dense populated cities like Tripoli to limit the horizontal expansion of the cities.Therefore, an accurate estimation of wind load is an important factor for the design of such tall buildings.This research examines the effects of wind on the design of buildings, and explaining wind types dominating territory. The thesis main focus is analysing the wind data collected from 22 meteorological stations distributed around the country.The wind data analysis is carried out by using a probability distribution model that created an estimation of the design wind speed with a return period of 50 – year for each city’s station.The established wind speed is then used to create a design wind speed contour map for the entire country using special software.
محمد بشير أبوهدامة (2009)

Abstract

The Nubian Sandstone Formation is a significant hydrocarbon reservoir in the Concession 59D, Eastern Sirt Basin, Libya. This formation is underlain uncomfortably by granitic basement and/or by the Hercynian unconformity and overlain uncomfortably by Pre-Upper Cretaceous followed by an Early Upper Cretaceous Transition beds. The Nubian formation is a thick sequence comprises mainly of sandstone, siltstone and shale.The Nubian Formation in this area has been subdivided into three stratigraphic members; namely Lower Sandstone, Middle Shale and Upper Sandstone (main reservoir well be focus of this study).The Upper Sandstone is the upper most subdivision of the Nubian Sandstone sequence consists mainly of white, grey to brown sandstones, ranging from fine to medium, locally coarse grained, moderately cemented with straight to concavo convex or slightly sutured grain contacts. This reservoir is a complex of fluvial sands deposited in Braided and Meandering streams.The reservoir fluids are very rich retrograde condensate gas and waxy oil with pressure at slightly above the saturation pressure. Most of this hydrocarbon in this reservoir has been sourced from the Nubian Middle Shale Member, but the Upper Cretaceous shale and Evaporates belonging to the Transition beds sequence have a significant potential source. The trapping mechanism in the field is a combined structural and stratigraphic trap for the Nubian Sandstone with the southern closure against the tight Nubian facies and basement of the Gialo High. Reservoir properties across the North Gialo Study Area vary in terms of porosity, permeability fluid saturation. These variations are indicated through the porosity, permeability and saturation maps and charts based on well log analysis and lab core sample measurements. These properties are discussed in the reservoir characterization part of this thesis.
عواطف عبد الله بودربالة (2012)