Petrographic and Diagenetic History of Cretaceous/Mesozoic Reservoirs and Their Impact on The Permeability Distribution Bapetco Field, Western Desert, Egypt.
- Maamoun Abdelrazik Wahdan (Bapetco) | Hassan Abdel Rahman (Bapetco) | Taher El-Zefzaf (Bapetco)
- Document ID
- Society of Petroleum Engineers
- North Africa Technical Conference and Exhibition, 15-17 April, Cairo, Egypt
- Publication Date
- Document Type
- Conference Paper
- 2013, Society of Petroleum Engineers
- 2.2.2 Perforating, 5.5 Reservoir Simulation, 2.4.3 Sand/Solids Control, 5.5.2 Core Analysis, 5.8.1 Tight Gas, 1.14 Casing and Cementing, 5.1.5 Geologic Modeling, 4.1.5 Processing Equipment, 4.1.2 Separation and Treating, 5.6.4 Drillstem/Well Testing, 1.6.9 Coring, Fishing, 5.1.4 Petrology, 5.1.3 Sedimentology, 1.8 Formation Damage, 1.6 Drilling Operations, 5.6.9 Production Forecasting, 5.2.1 Phase Behavior and PVT Measurements, 5.5.2 Construction of Static Models, 1.2.3 Rock properties, 5.1.2 Faults and Fracture Characterisation, 5.1.1 Exploration, Development, Structural Geology, 1.1 Well Planning
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A review of the available data of the Obaiyed field was carried out by Bapetco as part of the 2002 FDP update and the last review of Oct.2004. The Obaiyed field is a complex field, characterized by large uncertainties in permeability distribution and accordingly connected GIIP. The objective was to produce an integrated diagenetic and sedimentological model that can be utilized in 3D reservoir modelling. The study has resulted in a comprehensive 3D model of an estuarine, incised valley depositional system. Geological, Petrographical, sedimentological and Reservoir Engineering data have been integrated to create model realizations reflecting extreme scenarios of the permeability distribution within the field in an attempt to define their connectivity. The majority of the sandstone were deposited as bars within the estuary. The occasional higher permeability layers correspond to petrographic differences in the sandstones that relate to depositional sub-environment. Rock samples have been taken from the Paleozoic/Mesozoic in order to assess the diagenetic history, its impact on reservoir quality, and potential petrographic criteria by using the following analyses:
• Rock composition, Thin section petrography, SEM-analysis, XRD;
• Clay Mineralogy and Illite crystalinity;
• Age dating and Age of diagenesis: K/Ar-dating of Illite/Kaolinite concentrates.
The permeability and saturation distribution are a function of the diagenetic history of the field, causing the Paleozoic sandstones, which underlie the Mesozoic Lower Safa, to have a markedly lower permeability and generally lower saturation.
The Obaiyed gas/condensate field presents the challenging combination of a complex subsurface and a short timeframe to fully develop the field and to deliver committed daily quantities. The field was discovered in 1992, subsequently 4 appraisal wells were drilled between 1994 and 1996. After issuing the initial FDP in 1996 a development campaign was started in 1997, first gas was produced in 1999.
After drilling 28 wells in the area subsurface uncertainties have been reduced significantly, the current updated FDP focuses on the development of reserves locked in the tight parts of the field as a means to maximize profitability of the field. Currently over 50% of the in-place gas is locked in tight gas sandstones in the Obaiyed field.
In order to rule out other causes of poor productivity, the formation damage is the mechanism responsible for poor productivity. As this can only be done by ensuring no damage during drilling
Over the next two years, drilling activity in Bapetco will be increased, mainly because of the upcoming drilling campaign to develop the NEAG field In Abu El Gharadig Area and Obaiyed Area. Initial development plan will comprise drilling of 8-10 development wells in both Areas.
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