الفهرس 
Chapter (I) : IntroductionOnly 14 pages are availabe for public view
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Abstract
We can understand The reservoir characterization and tectonic evolution of the El Tamad Field area by using thirty 2D highly filtered stack seismic sections, five well logging data,17 thin sections and 8 SEM plates representing the cored interval of El Tamad area have been analysed While the geological and petrophysical data was used in building a 3D models of the El Tamad area.
El Tamad Field is considered as the first oil discovery in the onshore Nile Delta area. El Tamad discovery changed the philosophy of the hydrocarbon system within the Nile Delta area, wherein it provides a new play for exploration and production of Qawasim Formation beside Abu Madi Formation. The Field is located at approximately 15 km southeast of the El-Mansoura city and about 90 km north of Cairo, in the southern part of El Mansoura concession in the Northeast part of the onshore Nile Delta between Latitudes 30◦ 55’ 00´ʹ& 30◦ 57’ 00´ʹ N and Longitudes 31◦ 27’ 00´ʹ & 31◦ 28’ 00´ʹ E, covering an area about 5.8 km2.
The source rocks of El Tamad Field belongs to Late Cretaceous to Oligocene in age due to the presence of Oleanane (a biomarker for flowering plants) in the oil samples of El Tamad-1 which migrated vertically to the Upper Miocene of Qawasim sandstone reservoir in El Tamad Field. The geochemical analyses of El Tamad-1 oil sample advise that the oil is generated from a source rocks deposited in mainly lacustrine environment with marine clastic under oxic to sub-oxic conditions and containing mainly terrigenous organic matter type III kerogen. Moreover, the El Tamad oil seems to be come from source rocks at primary stage of mid-oil window maturity.
Qawasim reservoir at El Tamad Field is considered as the most productive hydrocarbon habitat and is considered to be most prospection objective in the field. Moreover, the shale of Kafr El Sheikh Formation represents an excellent seal rock for the Qawasim sandstone reservoir, which is characterized by stacked barrier-island bars with tidal effect depositional system. The entrapment of study field is related to combined type of stratigraphic and structural traps, that resulted from the influence of tectonic movements on sedimentary sequence.
The main target of the present thesis deals with 3D static modelling and reservoir characterization of Messinian sequences of Qawasim Formation in El Tamad Field with the aid of some available data from Mansoura Petroleum Company (five wells namely; El Tamad wells nos:1, 2, 3, 4 and 7). This can be done by constructing stratigraphic sequences and lithological correlation charts as well as isopach maps for the studied formations using Petrel software program. The microfacies, depositional textures, grain-types, porosity types, mineralogic percentages, diagenetic processes and facies distribution have been discussed. Petrophysically, porosity, water and hydrocarbon saturations, shale volume, gross thickness and net pay zones have been determined using Tech log and Petrel softwares programs. The relation between the pressure and depth plot help us in detecting the fluid contacts between the gas, oil and water. Detailed seismic interpretation of key seismic horizons have been undertaken in a computer software (Petrel software program version 2014) developed by Schlumberger.
Stratigraphically, the sedimentary sequence in El-Tamad Field wells is ended in the Upper Miocene Qawasim Formation. The Qawasim sediments of Late Miocene (Messinian) in age are mainly sandstones with shale and limestone-dolostone intercalations. These sediments are overlain by Early –Middle Pliocene shales of El-Sheikh Formation and El-Wastani Formation of lowermost Late Pliocene. The Pleistocene is represented by sands and clays of Mit Ghamr Formation. The maximum thickness of Qawasim Formation in the available wells is noticed in El Tamad well-1, and decreased towards the central parts of the field at El Tamad well-7. It is mainly composed of the upper sandstone unit (pay zone) which consists of sandstones with streaks of limestones, sandy limestone and shales; while, the lower shale/limestone unit consists of shales, limestones with some streaks of sandstones and siltstones.
Structurally,The structural setting of El Tamad Field is controlled by two major growth faults trending E-W direction parallel to the Hinge Line, downthrown in the north. These faults make a three way dip closures (El Tamad and North El Tamad) in the down thrown side. The closure of El Tamad Field has gentle slope towards the northeast and northwest directions, where three wells (El Tamad-4, 3 and 1) drilled in the crest of this anticline ; and two wells penetrated in a slightly down dip position; El Tamad-2 and 7. In addition a group of minor faults trending NE-SW and NW-SE directions with no affect on reservoir regime.
Seismically, The seismic interpretation of the top and base Miocene reservoir indicates the presence of a three normal faults F1, F2 and F3 trending E-W, NW- SE and NE-SW respectivelly. The F1 fault match with the hinge zone Late Jurassic- Early Cretaceous rifting (divergent between Gondwana and laurasia) which are rejuvenated in the Miocene and form the major growth fault (F1). While F2 and F3 match with the Miocene Red Sea- Gulf of Suez rifting. These faults are associated with differential vertical displacement, the growth fault (F1) downthrown in the north and associated with a rollover anticline fold that are formed in its hanging wall at its downtheown side while the F2 downthrown in the northeast and F3 downthrown in the southeast. The top and base of El Tamad reservoir was mapped in the term of depth domain which indicate that, there are a three way dip closures in El Tamad Field. It is found in the southeast direction and ended at the growth fault (F1).
Petrographically, Qawasim Formation at El-Tamad Field consists of clastic and non clastic facies. The clastic facies include conglomerate, sandstone and shale while non clastic facies include limestone and dolostone. The upper part of the Qawasim Formation is mainly sandstone which considered the main reservoir within the El-Tamad Field. It is classified into; arenite and wacke petrofaies associations. Arenite petrofacies include; subfeldspathic arenite, dolomitic subfeldspathic arenite, bioclastic dolomitic subfeldspathic arenite, glauconitic subfeldspathic arenite and Lithic subfeldspathic arenite, while wacke petrofacies includes Feldspathic wacke. Limestone facies are classified into; wackstone, packstone, boundstone microfacies associations. The wackstone microfacies includes mollusca foraminifera wackstone, while packstone microfacies includes algal bioclastics packstone, mollusca packstone, bioclastic packstone and foraminiferal bioclastic packstone and the boundstone microfacies includes algal boundstone. Dolostones are classified into; sandy bioclastic dolostone and algal bioclastic dolostone.
SEM showed that there are variable types of microporosity including; interparticle, oversize, intercrystal, intracrystal, vug, mold and frcturing porosity types. The Qawasim sandstones of El Tamad Field were affected by diagenetic processes, which enhanced porosity such as dissolution and dolomotization and destroyed the porosity such as compaction and cementation. Dissolution was primarily exhibited as partial to complete dissolution of feldspar grains and carbonate cement producing enlarged interparticle and oversize pores. The dolomitization process occurs in the calcite matrix and fossils of carbonate microfacies. Compaction is noticed in the form of mechanical and chemical processes resulted from the frcture of siliciclastic grains pore spaces giving straight and concavo-convex grain contacts. Cementation includes calcite and dolomite cements with relatively minor amounts of clays and quartz overgrowth. Recrystallization phenomenon also attacked the skeletal grains of carbonate microfacies in the form of aggrading of echinoids, algae, foraminifera and mollusca and also deggrading to algae. The formation of authigenic minerals is a result of the presence of unstable mineral grains, clay authigenesis is represented by authigenic clay which precipitate in some pore spaces in the reservoir decreasing the porosity and permeability.
Petrophysically related to primary structure, a comprehensive formation evaluation was carried out for the Qawasim Formation of El Tamad wells. The massive sandstone has a relatively a higher value of helium porosity (30.37%) than the laminated sandstones (30.24 %) while the value of dolomitic sandstone is 30.25 % that indicates that the quality of the reservoir is good. The values of helium porosity decreases gradually in the bioclastic limestone where it reaches 16.32 % and in the mudstone facies are 9.35 %. The most extreme value of the horizontal permeability has been found in the massive sandstones where it reaches 1770.43 mD while it is about 223.4 mD in the laminated sandstones. The dolomite crystals filling the connected pores that decrease the value of horizontal permeability in the dolomitic sandstones because it reaches 355.88 mD. However in the bioclastic limestone the value is 1.7 mD and in the mudstone facies is 0.85 mD. The most extreme value of the vertical permeability has been recorded in the massive sandstones where it reaches 847.13 mD while in the laminated, dolomitic sandstones, bioclastic limestone and mudstone facies the values are 431.78 mD, 232.23 mD, 0.72 mD and 0.082 mD, respectively.
The log data analysis revealed that the Qawasim reservoir has different thickness in different wells in the study area ranging from 9 to 139ft. Other spatial differences among the studies wells are good characterized (i.e. gross thickness, net thickness, net to gross, water saturation, effective porosity, shale volume and hydrocarbon saturation). Qawasim zone 2 was interpreted to be the main pay zone.
The calculated total porosity (Øt) of Qawasim zone 2 (mainly sand reservoir) increases towards the southeastern part of the studied field where a maximum value has been recorded at El Tamad well-4 (27.8%) while the minimum value at El Tamad well-2 (19.1%). Similarly, the effective porosity (Øeff) increases towards the southeastern part of the present area with a maximum value (23.65%) at El Tamad well-4 , while the minimum value at El Tamad well -2 (15.58%). The shale volume/content (Vsh) is relatively low at the southeastern part at well-4 and south western parts of the field at well-3, while it reaches a maximum of 22.1% toward the central portion of the field at well no-7. Also, the water saturation (SW) increases towards the central part of the study field with a maximum value of 44.4% in El Tamad well-7. On the other hand, a minimum value of 22.1% has been recorded at El Tamad well-4. The hydrocarbon saturation (Shr) increases towards both the southeastern at well- 4 and southwestern at well-3 parts with a maximum value of 77.9% in El Tamad well-4, while the minimum value is recorded at El Tamad well-7 is 55.6%.
The gross thickness increases toward southeastern at well-4 and southwestern at well-3, with a maximum value of 139in El Tamad well-4. On the other hand, the minimum value is recorded at El Tamad well-7 reach to 9. The Net pay increases toward both southwestern at well-3 and southeastern parts at well-4 with a maximum thickness encountered in El Tamad well-3, while the minimum thickness found in El Tamad well-7. The Net/Gross ratio increases toward the central part of the studied field at well-7 with a maximum value of 1. In contrast, the minimum value is 0.4 which recorded at El Tamad well-2.
from the petrophysical parameters, we can conclude that El Tamad well-4 has the maximum hydrocarbon saturation in addition to maximum effective porosity (Øeff) with minimum volume of shale (Vsh). Furthermore, the line connecting El Tamad wells 4, 3 and 1 in the southeastern part of El Tamad Field has the best reservoir quality for future drilling and production development.
The main reservoir in El Tamad Field is comprising gas, oil and water where the gas oil contact (GOC) has been recorded at -6400 TVD.SS (6430 ft. MD) at El Tamad well -1 with gas gradient value of 0.08 psi/ft and oil water contact at -6420 TVD.SS (6450 ft.MD), with oil gradient 0.26 psi/ft. In El Tamad well -2, the oil water contact (OWC) has been recorded at -6420 TVD.SS (6622 ft.MD) with oil gradient 0.26 psi/ft, and water gradient of 0.45 psi/ft. while in El Tamad well -3 the gas oil contact is detected at -6400 TVD.SS (6645 ft.MD) with gas gradient 0.08 psi/ft and oil water contact was detected at -6420 TVD.SS (6682 ft.MD) with oil gradient 0.26 psi/ft.
The iobtained i3D Static model iprovides ia iuseful imeans itowards iunderstanding ithe inature iand icharacterization iof El Tamad ireservoir. i iA idirect irelation ibetween ithe ifacies ichanges iand ipetrophysical iproperties iis inoticed. A i3D istructural imodel iis ibuilt iby iusing ithe ioutput iof ithe iseismic iinterpretation. This imodel illustrates the presence of three main faults trending E-W, NW- SE and NE-SW downthrown in the north, northeast and southeast respectively. The ifacies analysis ireflected ithat ithe El Tamad reservoir iwas ideposited iunder stacked barrier-island bars with tidal effect as we can dedued from the ifacies imodel. A i3D ipetrophysical imodel ishows ian iincrease iin ieffective iporosity iin ithe both of southeastern and southwestern parts of the study area around well-4 and 3 iand idecreases ias igoing ito northwestern toward well-2, iFor ithe iwater isaturation ithere iis idecrease iin ithe southeastern ipart iaround well-4 iand iincrease ias igoing ito centre itoward well-7i, For the net to gross model, there is increase in the direction of centre where the well-7 located. Finally the fluid contact model show that, the study area contain three different types of fluids including gas, oil and water.
Recommendations and furure work
Results of the present study proved that the petrophysical characteristics of Qawasim sandstone section reflect the ability to store and produce hydrocarbons. Therefore, we recommend to perforate more wells around the line connecting El Tamad wells 4, 3 and 1 in the southeastern part of El Tamad Field because it has the best reservoir quality for future drilling and production development and the wells contain the suitable petrophysical parameters of hydrocarbon saturation, effective porosity (Øeff) and volume of shale (Vsh). These wells should put under production test wells to gain more amounts of hydrocarbons. Drilling of sidetrack wells in this line should be followed in the strategy plan of the powered company upon the concession.