الفهرس 
CHAPTER II GEOLOGIC SETTINGOnly 14 pages are availabe for public view
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Abstract
Balsam field is onshore Dana Gas field located in the Nile Delta region, West El Manzala Concession between Longitudes 30° and 32°E, and Latitudes 30° and 32°N. Data for five wells had been obtained from Dana Gas Company and EGPC for Balsam field considering 5 wells: Balsam-1, 2, Balsam-3ST_2, Balsam-4 & Balsam-5. Based on the available data; the whole stratigraphic section of Balsam field of five wells had been investigated regarding petrophysical, sedimentological and geomechanical aspects in relation with drilling challenges with major focus on Qawasim reservoir section for three main reasons as follow
• Qawasim reservoir represents the main reservoir in the field, usually the reservoir section covered with decent and enough data.
• The reservoir section exhibited the most severe drilling challenges.
• The reservoir section prone for reservoir damages potentialities such as fine migrates due to downhole losses that affected the overall well budget.
Using the Techlog, A Schlumberger software; all electrical logs utilized initially to delineate the general lithology of drilled wells along with mud log and final well reports, in the meantime the same data considered to calculate most of the petrophysical parameters such as formation porosity, density, water saturation, volume of shale (Vsh) and calculated permeability. The cross-plots of density-neutron utilized to detect the lithology meanwhile the Th-K cross plots utilized to define the clay mineralogy. Kafr El Sheikh Formation petrophysical analysis shows 16 – 24% porosity and 27–30% shale volume, whereas Abu Madi Formation shows 12 – 15% porosity and 15 – 27% shale volume. Qawasim Formation porosity ranges from 13 % to 20%, whereas the volume of shale Vsh ranges from 13% to 31%.
Based on empirical formulation; the Abu Madi Formation permeability ranges from 62 – 150 mD , whereas Qawasim Formation permeability is at 300 to 500 mD. The data was validated with core permeability data from EL Basant field in addition to W. Dikirnis, and W. Khalila offset fields . All the tight spots , hole reaming and back-reaming, losses and differential sticking were associated with reservoir intervals of high porosity indicating that the rock need to be strengthen utilizing the optimum wellbore strengthening materials.
Permeability data utilized to re-design the wellbore strengthening material using Kaeuffer rule method utilizing Baker Hughes GeoWise Software (wellbore strengthening software). The Model utilized to properly design the bridging materials for Qawasim reservoir to minimize the differential sticking challenges and reservoir damages for the future wells. The volume of shale (Vsh) and clay mineralogy utilized to suggest the optimum shale inhibitive materials of drilling fluids to avoid the wellbore stability-related issues for incoming wells planned to be drilled through the same reservoir.
Based on calculated permeability data from petrophysical analysis ; a certain particle size of acid soluble calcium carbonate and bio-degradable powdered cellulose were recommended to strengthen the reservoir as non-damaging materials. Drilling fluids utilized to drill the reservoir section has a potassium chloride in the formulation to inhibit the clay, however Th/K Ratio cross plots indicate a presences of kaolinite, so it is highly recommended to consider the Polyamine technology instead of potassium chloride that easily can convert the kaolinite clay type to dispersive illite and create fine migrates and damages the reservoir and reduces the well productivity.
To properly understand sedimentary environments and litho-facies; petrophysical analysis including cross-plots along with mud logging data and nearby published sedimentary & petrophysical data on El Basant, in addition to both W.Khilala and W. Dikirnis fields utilized to define and categorize the litho-facies of Qawasim reservoir. Generally, Qawasim Pay I consists of shale with sandstone and siltstone streaks, meanwhile Qawasim Pay II consists of sandstone with, shale and siltstone streaks.
The facies are identified based on grain size, sand/mud ratios, sedimentary structures, contacts from cores and borehole image logs of offset published data on El Basant field in addition to both W. Khilala and W.Dikirnis Fields.
The six main lithofacies include massive sandstone, cross-stratified, flaser bedded sandstone, tidal heterolithics, deformed heterolithics, and massive to laminated mudstone.
Drilling and geomechanics events analysis obtained from drilling reports and final well reports of mud logging. A lot of tight spots, reaming and back reaming after tripping and differential sticking recorded for 5 wells.
All the petrophysical, sedimentological and geomechanical analyses were integrated to understand the root causes of drilling challenges and propose a completed solution. The main root causes of drilling challenges in Balsam filed include the following:
• Drilling through a High porous and permeable formation at 22% and 500 mD with high shale volume that reaches 30%.
• Drilling overbalance on Qawasim Formation at about 2500 psi.
• Drilling formation of different pressure regimes that ranges from 9.00 – 11 ppg pore pressure.
• drilling through different sedimentary environments such as distal tidal bar, proximal tidal bar, tidal channel, and estuarine facies associations that always exhibit an intercalated sediments and prone to a weak bedding plane. those weak bedding planes behaves like high permeable paths, so easily drilling fluids would extrude along betting planes and disturb/weaken the rock that result in a breakouts, stuck pipe or hole collapse.
• Drilling the hole sections with non-inhibitive water-based mud that is missing proper wellbore strengthening and optimum chemical inhibition.