No abstract

The Eastern Mediterranean region, extending from the Offshore Nile Delta Cone of Egypt to the Levant Basin, is a confirmed hydrocarbon-rich territory with several giant gas discoveries. Numerous gas fields have been discovered in the Miocene reservoirs within the Nile Delta Cone, and the Levant Basin. The Miocene sedimentary sequences in this region are extremely heterogeneous, consisting mainly of turbiditic slope deposits, channels, and basin floor fans that were capped by evaporites formed during the Messinian Salinity Crisis. As a result, the seismic characteristics and interpreted properties of this heterogeneous section are ambiguous. The study area is located in the Offshore North Sinai Basin, where a thick Early Miocene section was deposited midway between the Nile Delta province, which includes the El-Fayrouz discovery, and the Levant Basin, which includes Tamar, Tanin, and several other discoveries. This study uses quantitative seismic interpretations methods, such as amplitude variations with offset and fluid replacement modeling, to assess the seismic acoustic impedance trend with depth. Also, determine the seismic amplitude response for the brine and gas sands reservoir of the Early and Late Miocene section to link the unexplored study area within the North Sinai Offshore Basin with the explored Nile Delta and Levant Basins. In addition to evaluate direct hydrocarbon indicator (DHI) of the dimming seismic amplitude that is compatible with the structure’s last closed contour of the Syrian Arc anticline of the Early Miocene reservoirs (EMT-1 prospect). Different vintages of 2D and 3D seismic data, six wells, and various published data were used in this study. The quantitative interpretation shows the pitfalls of the acoustic impedance trend and seismic response dependency on depth for gas and brine sand, which led to the drilling of the EMT-1 dry well. Also, the fluid replacement, P-wave velocity (Vp), and density (ρ) modeling confirmed that the seismic dimming amplitude was due to a seismic processing artifact, which was corrected by readjusting the overburden Messinian salt processing velocity model. This research concludes that the seismic quantitative interpretations are successfully used to assess the acoustic impedance versus depth and understand DHI pitfalls, as well as the processing workflow that could enhance the seismic image.

This study has been focusing on planning wells, which target lower Pleistocene reservoirs below a depleted Ha'py gas field. Many Non Productive time events (NPT) have been anticipated, and the challenges of losing wells and running over budget have been considered as major risks in targeting the deeper prospects. Years of production from the main Pleistocene A20 reservoir has resulted in significant pressure depletion, while underlying largely-undeveloped Pleistocene reservoirs appear to be very promising they remain at or close to virgin conditions. In addition, the position of the platform at the centre of the field has made it necessary to drill highly-deviated wells to access remaining reserves at the crest of the field. Detailed planning and close collaboration between the PhPC (Pharaonic Petroleum Company) subsurface and drilling teams has been necessary to understand the geological and geomechanical properties of the key formations. This has helped in selecting appropriate mud rheology and mud additives in addition to ensuring good drilling practices that maximise safety and success. The combined effects of depletion and low rock strength make it effectively impossible to drill the A20 interval with the mud weights required to minimize well bore instability. As a result, stress cage additives were employed in the drilling mud in order to reduce the potential for losses due to the large overbalance against the depleted sand. Modeling prior to drilling suggested this application lay close to the technical limit of the stress cage methodology, and was beyond anything previously attempted within the Pleistocene reservoirs in the offshore Nile Delta. Careful execution meant we were able to successfully drill through the depleted zone, and as a result of this work, we have been able to deepen recent wells to access underlying gas resources. This success has allowed us to reduce NPT while ensuring safe well operations.

The Lower Rudeis Formation is an active source rock in the Garra region, which is characterized by a good hydrocarbon generative potential. The Lower Rudeis source rock reached the early mature stage in the Middle Miocene Langhian (15.5 Ma) and went through the mid mature stage at 0.9 Ma.. It was generated from a clay source rock, deposited under sub-oxic to oxic conditions and derived from an organic material composed mainly of terrestrial organic material. The Lower Rudeis source rock went through two phases of hydrocarbon generation and expulsion. The first phase occurred from 6.0 Ma to 3.4 Ma, while the second phase started at 3.4 Ma and continued until the present time, with a transformation ratio estimated of 42%. The oil expulsion increased to 16 mg/gTOC and gas expulsion to 40 mg/gTOC, thus the expelled hydrocarbons are mainly composed of mainly gas and some oil. In contrast to the southern province, the Garra region has a single petroleum system which is charged by pre-Miocene and Miocene, Lowers Rudeis, source rocks along vertical and lateral migration routes and the main Kareem-Rudeis reservoirs that were sealed by the Belayim evaporite. The current study is based on the geological, geochemical, biomarker and stable carbon isotope data, which were analyzed, interpreted and presented as burial, thermal and maturity models using the petroleum systems and basin analysis program (BasinMod software).

Exploration drilling in the Nile Delta has dramatically risen over the past 3 years, jumping from 5-10 wells/year up to 20-25 wells/year. Much of this recent drilling has been targeting the highly successful Pliocene play trend and the 2008 industry success ratio approached a phenomenal 90%.Thick sequences of Pliocene deep marine sediments have been successfully drilled and led to several offshore gas discoveries. No great exploration interest had been directed towards these good reservoirs in the onshore areas of the Nile Delta. Nevertheless, Dana Gas has been one of the most active and successful operators for this exploration target in its West El Manzala and West El Qantara Concessions.The gas sands of the Pliocene reservoirs are characterized by low velocities and densities compared with the surrounding shales and, subsequently, the top and base of the reservoirs have a "bright" seismic amplitude response. Additionally, the gas charged Pliocene reservoirs are often associated to acoustic impedance anomalies presence. The key challenge in the Pliocene reservoirs exploration is to understand the depositional environment with respect to the amplitude and acoustic impedance geometry from 3D seismic data through the cross-correlation between seismic facies character and the depositional pattern and environment. The main features and variations recognized in the reservoirs drilled to date in West El Manzala andWest El Qantara Concessions show a slow activity in the main basin evolution stage that seems to be not affected by high turbidity current flow or significant slope channeling. The early stage broad and straight channel system valley was cut and filled by younger channelized systems. Minor incisions of channel cuts are considered to be a key feature in defining channel fill development and sand distribution. SPE 127815A comprehensive study has been made recently on the Pliocene sequences in West Manzala and West Qantara concessions to assess the potentiality of El Wastani and Kafr El Sheikh Formations which represent the main reservoirs for the Pliocene sequence. The study has been focused on sequence stratigraphy analysis of the entire sequence to understand the depositional setting of the area through time as a fundamental support to the prospect generation and ranking of the area.The presence of shallow dry gas reservoirs with good productivity combined to a relatively cheap drilling cost makes the Pliocene exploration very attractive and economically profitable even for small accumulations. SPE 127815 3