Abstract
The shallow clastic section in the Nile Delta is characterized by mild velocity variations. The relationship between the expected velocity reduction in the gas reservoir rocks and the encompassing shale is responsible for acoustic impedance contrast, predictable to a particular AVO-class. In class-3AVO, the bright spot is a result of great reduction in velocity increase due to differences between high-velocity encompassing shale and relatively low-velocity reservoir sand. The class-3AVO characterizes a strong seismic amplitude appearance in the full stack section and with similar characteristic view of AVO analysis and interpretation. In addition to the strong amplitude, there are different DHI features related to the gas occurrence. These DHI features are analyzed to achieve and deliver a successful exploratory well. The DHI analysis of one of the unsuccessful cases using recent 3-D seismic data clarifies the importance of the workflow that works for exploring types of anomalies in the Nile Delta. The anomaly is drilled mainly based on an explicit high-amplitude anomaly with local flat spot, but without taking into consideration the extent of DHI characteristics, inherent to gas occurrence in the Nile Delta. Authors investigate all the features related to this unproven case in the form of a postmortem and compare it with proven existing discoveries, to know the possible reason of unsuccessful DHI anomalies in the Nile Delta.
Highlights
The area under study (Fig. 1) is located in the most northern part of Egypt between longitudes 30.2 to 32.2 and latitudes 29.8 to 32.8.According to the literature (El Heiny and Enani 1996; Sarhan et al 1996; Deibis et al 1986 and Payton 1977), the environment of deposition of the area under study varies from deep marine in the deeper part to shallow marine and deltaic facies in the shallower part
Mega slumps were active during Late Pliocene to recent
In Andaleeb low-resistivity gas discovery, the main target for the well testing was anomaly 25, which has a porosity ranging from 22 to 28% in the cleanest thin layers and water saturation within 40 and 60% (Farias et al 2010); in Karous gas discovery, the reservoir extends over 78 m of gross pay, while the net pay 49 m and porosity is over 30% (Barsoum et al 1998)
Summary
The area under study (Fig. 1) is located in the most northern part of Egypt between longitudes 30.2 to 32.2 and latitudes 29.8 to 32.8. The seismic interpretation of the post-salt section is based on extracting the seismic amplitudes, their anomalies zones and comparing them with existing one. These amplitude anomalies are analyzed in sequence; firstly, the highlighted anomalous zones are analyzed with different features related to strong amplitude and possible gas accumulations, as flat spot and pull-down effect. Different DHI features related to the successful cases in the Nile Delta Pliocene section are analyzed (Hanafy et al 2014) as follows: 1. Well_1 main target is anomalous high amplitude in full stack section
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