المنشورات العلمية لـجامعة طرابلس

احصائيات منشورات جامعة طرابلس

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Stratigraphy and Depositionalenvironment of Abu Ahaylanformation - NW Libya

Abstract

Seven geological sections have been examined and sampled with emphasis on sedimentological & diagenetic processes within Abu Ghaylan Formation and the contact relationships with the underlying Abu Shaybah and overlying Kiklah Formations. Based on current detailed field loggings and microscope investigations, 10 facies are recognized within Abu Ghaylan Formation. The lowermost succession characterised by an overall transition from continental fluvially dominated deposits of the Abu Shaybah Formation into transitional to marginal marine, tidal flat deposits of the Abu Ghaylan Formation upward. The transitional nature of this lowermost part succession is demonstrated by interbeddings of claystone, sandstone and fossiliferous facies arranging in coarsening up cycle, in which most probably deposited in estuary / beach environment.The Abu Ghaylan Formation generally wedges laterally eastward and exposes intermittently east of Wadi Ghan area resulting of syngenetic uplift of Wadi Ghan area followed by erosion (ElHinnawy & Cheshitev, 1975). A slightly earlier uplift and greater erosion in a westward sloping basin of deposition near the close of the Early Jurassic and Early Cretaceous times is suggested by Fatmi & Sbeta (1991). The current study reveals that several exposure surfaces are demonstrated within Abu Ghaylan Formation suggesting uplifting and erosion episodes interrupted Abu Ghaylan Formation, where a restricted distribution of Abu Ghaylan may suggest a local tectonic overprint.Although the overall impression is that the base beds of Kiklah Formation starts with sandstone and red clay beds as channel infill deposits above Abu Ghaylan carbonate unit with surface of unconformity, however, based on current close investigation, a sequence characterized by interbeddings of carbonate and greenish clay overlying Abu Ghaylan Formation with surface of unconformity and gradationally overlain by sandstone beds should be introduced as separate unit attributes to Kiklah Formation.The current study emphasizes and supports a solution collapse origin for the breccias and introduces better insight into architecture and geomorphology of the breccias bodies that are exposed in the area of study. The dissolution of evaporites is considered responsible for all breccias development in this stratigraphic interval. According to the occurrence mode of breccias, the breccias intervals have been divided into two main parts; a lower section of strata that contains collapsed paleocaves and an upper section of strata that is deformed to varying degrees due to the collapse and compaction of the section of paleocave-bearing strata. The sharp flat base, inverse grading, V-shaped/ sag structures and irregular undulating top of brecciated bodies are recognized within Abu Ghaylan Formation and typically characterize solution collapse processes. Based on field study and architecture relationships, five distinctive karst facies are recognized in the area of study.The early diagenetic genetically related processes probably interrupted the deposition of Abu Ghaylan Formation is a most possible assumption for the origin and timing of breccias formation.
أحمد أبوبكر الحلو (2015)

قواعد الاستقلالية بين التطبيق العملي والتطوير

Abstract

Taking in account the importance of the auditor’s independency and considering it the Most important feature the auditor must possess, Where it is considered the basis of The auditor’s profession and the main reason for its existence in the society; and in Attempt of studying the real audit standard exercised in Libya and the extent of its Success in achieving the objectives that it was set for.This study conducts a research on the independent rules actually implemented in Libya and on what standards it refers to; nevertheless, its research is based on to what Extent the independent rules mentioned in the standards of the international auditing Are suitable as a basis for the ideals of auditing to be relied on in Libya.There's a problem in studying the standards of independence implemented in Libya And its nature, in reference to the source of issuing and level of distribution of each Practice in between Libyan auditors and to the extent of Success of these standards Implemented to achieving its aims. From another aspect, this study aims to investigate the compatibility and suitability of The rules of independence enlisted in the International Auditing Standards with the Vocation practices in Libya.The study focused on three main assumptions: The first - There is no general agreement on particular standards followed by .Libyan Auditors. The second - the present situation for auditing in Libya does not suit the Libyan Environment and is not appropriate for organizing professions in it. - The third - the rules of independence enlisted in the International Auditing . Standards are not consistent with the vocational practice in Libya.The study was divided in two parts Oral and Practical.The Oral part composed of three Sections. - The First section was an introductory included the problem and the Essentials of The study and all previous studies and the pursued program of study. - The second section consisted of the standards of auditing, as of what it is and the Sectors responsible for the issuance of the standards in countries and the standards of Auditing in Libya.. -The Third section related to the independence of auditing and the risks of Independence and the independence of auditing in Libya.The Practical part composed of two Sections.The first section includes the clarification of the pursued program of study in the Practical study in this research, relating to society; and the case of study include: The society of study consisting of all auditors who practice the profession of auditing Via Legal auditing Offices in Libya and the case of study was limited to the auditors Who work in this profession and their offices location are in the Center of Tripoli. The Auditing Offices in the Center of Tripoli were chosen by the first society of Study; as a first step; in addition choosing randomly a case from the auditing offices Working in the city of Tripoli. Which summed up to 61 offices in the second step.We used a Sheet of Questionnaire to collect the needed data from the case of study And this procedure was chosen because it was consistent with the program of study. The sheet of Questionnaire included 47 questions; Therefore, it was divided to four Main parts : - Part - 1 Information on the filling of the questionnaire. Part - 2 Information on the Standards of auditing practiced in Libya. Part 3 Information on the effectiveness of the standards practiced in Libya. Part - 4 Information on the extent of consistency of the rules of independence enlisted In the International Auditing Standards with the professional practices in Libya.The Sheet of Questionnaire related to the study was distributed to the chosen case of Study of Libyan auditors who practice the profession of auditing in the city of Tripoli, where the number of participants who answered the questionnaire and who Were contacted by the researcher reached 122 legal auditors who represent 61 Auditing Offices. This number represents the intended auditing offices, the owner, and group of partners and other auditors who work there. Where the average of the answers represent 90% of the distributed sheets, then the Statistical analysis for the received data in the questionnaire have been programmed By the computer by using the statistical SPSS Program for analyzing these data then By emptying the received answers from sheets of questionnaire in computer and Making dual analyzing for the data to achieve the results of the study.In the end of her study, the researcher concluded to accept the assumptions of this Study and to point out that the standards of auditing that the Libyan auditors Implement is a combination or mixture of a variety of American, British and International and this mixture is not suitable for organizing professions in Libya and The rules of independence that are enlisted in the International Auditing standards is Not consistent with the Professional practice in Libya.The most essential recommendation that the researcher emphasizes in the end of her Research is to put local auditing standards that bear features of the Libyan Environment and the characteristics of the Libyan auditor or depending on International standards and rectifying them with what is compatible with the Libyan Auditor and. Environment Socialist Peoples Libyan Arab Creat.
أسمهان علي موسي (2008)

Formation Pore Pressure and Fracture Pressure Gradients versus Depth Correlations for Sirte Basin (Libya)

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)

Using Maximum Entropy Principle (MEP) to Assess Wind Energy Potential in Libya. Case Study Dernah

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)

Geological study of the Early and Late Cretaceous Clastic Reservoirs in C-structure, Block nc-98, Al hameimāt Trough, Sirt Basin-Libya

Abstract

The area of study is located in the southeastern part of Block NC98 and is informally named C-Structure area, and it is completely situated in the center of Al Hameimāt Trough, South East Sirt Basin, Libya. The main reservoir rock in this structure is the Upper Nubian Sandstone Member, whereas the Reworked Sandstone Unit and Transitional Beds are considered as secondary reservoir rocks. These reservoirs are mainly composed of sandstone to argillaceous sandstone. The Upper Nubian Sandstone reservoir quality is adversely affected by volcanic rocks especially the thick intercalation of volcanoclastics within the Upper Nubian Sandstone. The Upper Nubian Sandstone Member was deposited during Early Albian times. The Reworked Sandstone Unit was possibly deposited in Cenomanian? to Turonian times and may be related to the overlying Transition Beds.Up to date, four wells have been drilled in this structure (C1-NC98, C2-NC98, C3-NC98 and C4-NC98) and were targeting the clastic reservoirs of the Upper Nubian Sandstone and/or overlying Upper Cretaceous Transitional beds and Reworked Sandstone unit. Only C1-NC98 and C2-NC98 wells have tested significant hydrocarbon in the Upper Nubian and Reworked Sandstone unit whereas C3-NC98 and C4-NC98 wells have tested no hydrocarbon in both reservoirs and are abandoned as dry wells. This study is aimed to validate the stratigraphical aspects, depositional environment and reservoir quality assessment in order to decipher the reasons of drilled dry holes. The obtained results are anticipated to provide valuable geological information for the current and future prospect evaluation in the area. All available wire line logs of C wells (C1-NC98, C2-NC98, C3-NC98 and C4-NC98) and adjacent wells have been used to correlate the stratigraphy of the Pre-Upper and Upper Cretaceous silisiclastic sediments in the area of study.Representative core samples across the reservoir rocks of the candidate wells have been laid down for core description. The acquired results have been integrated with conventional core analysis and petrographic results to investigate the lithofacies characterization and depositional environment in order to sub-divide them into different lithofacies.Different types of geological maps have been prepared in this research (e.g. stratigraphical/structural cross sections, subcrop maps, isobach maps, structure contour maps and etc.) to delineate the formation extension and correlation. Burial history diagrams across all depositional sequences in the candidate wells were also prepared to identify the depositional scenario and to estimate the time span of tectonic subsidence along the depositional sequences.The results of all available geological studies which recently have been carried out by Waha Oil Company in the area of study and adjacent areas have been reviewed, elaborated and integrated with the results of this study to assess the discussion and final conclusion. The final results of sedimentological study indicates that there is no major effect of diagenetic processes on the reservoir rocks during and after the deposition. As a consequence, C3-NC98 and C4-NC98 wells were drilled in an area of poor reservoir quality of Reworked Sandstone and Upper Nubian reservoirs due to the existence of thick sequences of clay and siltstone which were mostly deposited in levee and over bank sub-environments of likely combined braided and meandering river. Whereas, C1 and C2-NC98 oil wells were drilled in an area of good reservoir quality of Reworked Sandstone and Upper Nubian Sandstone reservoirs where the sand bars sub-environment are deposited as a thick sequence of clean sands carrying the genetic of good reservoir properties. Therefore, the reservoir rocks in this area have different properties due to different sub-environment of deposition. This new results will probably assess the prospect generation and evaluation for the future drilling activity in the area of study.The encountered volcanoclastic sediments in well C2-NC98 reveals that this sediment is likely transported by river from the area of volcanic eruption to the area of deposition rather than in situ eruption. This type of volcano is likely applied to cinder cone volcano type where the pyroclastic fragments are not cemented together and thus easy to erode. Therefore, the intercalation of volcanoclastic sediment in Upper Nubian Sandstone has no marked effect in the reservoir rocks.Burial history curves of wells C1-NC98, C2-NC98, C3-NC98 and C4NC98 indicate three major subsidence events took place during Early Cretaceous time (Early Aptian - Early Albian), Late Cretaceous time (Turonian - Maastrichitian) and the Palaeocene - Eocene subsidence. However, Plaeocene - Eocene subsidence shows the highest subsidence rate with comparison to the other two subsidence rates.
محمد عمار هامان (2015)

The Basaltic Intrusions of Central Jabal Nefusah Foothills

Abstract

The basaltic Intrusions of the Central Jabal Nafūsah Foothills which extend from NW Wādi Zāret to NE Wādi Ghān Dām are part of the latest stage of Gharyān Volcanic Province (GVP). These intrusions are classified on basis of their shape and mechanism of emplacement into four kinds of volcanic bodies. These are; sheets (dykes and a sill), dykes associated with volcaniclasts, volcanic cone and lava mounds. Generally, the dyke emplacements are restricted only to the area between Wādi Zāret to Abū Ghaylān, while the other forms extend from Rās al Mazūl Dome to Wādi Ghān Dam. The more differentiated rocks are restricted to the area between Rās al Mazūl Dome and Wādi Ghān. Farther west towards Wādi Zāret, ultramafic xenoliths and magnesium-number increase, suggesting closer proximity to the source. The rocks are essentially alkaline with within Intraplate signatures. They straddle the composition from picrites, basanites, alkali basalts through hawaiites, mugearite to benmoreites with a compositional gap between the last two types. Generally, the phenocrysts are represented by foresteritic olivine, Cadiopsidic pyroxene, magnesiotaramitic amphibole, plagioclase, K-feldspar and titanomagnetite. The chemical composition of the mafic minerals indicates that they are high pressure phenocryst phases. The most primitive picrites satisfied the criteria of primary mantle melts. The rocks are generally, enriched in LILE suggesting an enriched mantle source. The studied rocks were grouped into five groups based on incompatible trace element ratios; Group-A includes picrite, basanites and hawaiites, and Group-B includes picrite (Z-3), basanites , alkali basalts, and hawaiites, while Group-C is formed of hawaiites, Group-D is composed of mugearite and Group-E is made up of benmoreites. Picrites and basanites of these rock have high Mg-number (>0.64), high Cr and Ni contents and strong light rare earth element enrichment, but systematic depletion in Rb, K and Ba relative to trace elements of similar compatibility in anhydrous mantle. Alkali basalts and more differentiated magmatic rocks have lower Mg-number and lower abundances of Ni and Cr, and have undergone fractionation of mainly olivine, clinopyroxene, Fe–Ti oxide, amphibole and plagioclase. The variation in the concentrations of major, trace, rare earth elements, and incompatible element ratios in the rock samples demonstrate the heterogeneous character of their source region. Such heterogeneity can be interpreted by the involvement of a heterogeneous mantle reservoir to different degrees of partial melting. The REE data require residual spinel stability peridotite field in the source and constrain the melting process of Group-C and Group-D to 2% to 3.5% degrees of melting respectively, Group-A and Group-B both to 5% degree of partial melting while Group-E to 10% degree of partial melting of spinel lherzolite xenoliths of Al Ourban area. Mass balance modelling of the major suggests two possible FC scenarios; Derivation of basanites and hawaiites of group-A from G-3 picritic parental magma. Derivation of Group-D and Group-E was also possible from these basanites. Derivation of basanites of Group-B from Z-3 picrite parental magma and simultaneous derivation of G-4 and QJ-1 alkali basalts from Z-3 picrite parental magma. V Simple mass-balance calculations suggest that the melting assemblages of picrites and basanites consisted of forsteritic olivine, diopsidic clinopyroxene, Ti-magnetite. While the alkali basalts and more differentiated magmatic rocks, mass-balance calculations suggest that the melting assemblages consisted of sodic plagioclase, magnesiotaramitic amphibole, diopsidic pyroxene, Ti-magnetite, K-feldspar with sub amounts of apatite and sphene.
سمية عون (2015)

Voltage stability of the Libyan network after its enhancement by new stationary and mobile units and new 220-400KV transmission Lin

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)

Helmholtz resonator analysis

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)