Baltim Concession is a large exploration/exploitation license located in the offshore Nile Delta, Egypt. The concession covers an area of 430 Km 2 of the central portion of the present dayNile delta cone. High quality three dimensional (3D) seismic data, coupled with data from some wells drilled in the area, have highlighted the presence of some gas chimneys well recognizable started from pre-Messinian until the Plio-Pleistocene slope succession. The geometry and architecture of the gas chimneys in Baltim area have been imaged by 3D seismic techniques, time section and a variety of attribute extractions, providing us with a high resolution definition of these features. The main indicator for gas chimneys in seismic is an almost cylindrical shaped chaotic behavior of seismic signal, due to scattering of seismic energy by diffused gas through the cap rocks above the leaked reservoirs. The origin of gas chimneys has to be related to hydraulic fracturing by gas leaking through faults from deep accumulation where overpressure conditions have been generated by fast burial during the Plio-Pleistocene mega sequence deposition. The petroleum system in Post-Messinian (Plio-Pleistocene) succession generated biogenic gas only, whereas the Pre-Messinian system proved to generate thermogenic gas and oil. The role of gas chimney and associated structures as hydrocarbon migration pathways from the pre-Messinian kitchen section to the Post-Messinian reservoirs is testified by many DHI's within the Pliocene -Pleistocene reservoirs that are in contact with the boundaries of the gas chimneys. In addition, geochemical analysis on gas samples from targets drilled in the Pliocene -Pleistocene indicates the presence of thermogenic gas clearly generated from pre-Messinian units. From isotopic data, PVT samples and production data from gas fields discovered in Plio-Pleistocene succession evidenced that in many cases gas migrated from the pre-Messinian through high fracture zones related to gas chimneys activities in the studied area.
Nile Delta Basin is a mature gas producer in Egypt, from the early sixties till present many gas discoveries were made in both on & offshore areas in the Pliocene and Miocene reservoirs. The first gas field, Abu Madi Field, was discovered onshore Nile Delta in 1967, by AGIP (IEOC) with the drilling of the Abu Madi-1 (AM-1) well. The Abu Madi field started to be developed since 1970, it's producing wells increased to 21 and by end-1992, the field had a capacity of 400 MCF/d; being that time the biggest gas field in Egypt. Subsequently of the gas-bearing reservoir discovered in Abu Madi Formation (Late Messinian) -becomes one of the main targets in on and offshore area of Nile Delta. The stratigraphic framework of the Abu Madi Fm., was reveal through years, now a days this formation is considerate as a sedimentary infilling of a fluvial paleovalley characterized by stacked fluvial-deltaic sandstone and shale's. The classical Abu Madi Fm., lithostratigraphic layering comes from the Abu Madi/El Qaraa fields where the reservoirs sandstones levels have been named, starting from bottom, as follows: Level 3 (Lower, Main, Upper and 3A), Lev2 and Lev 1. The recently wells targeting the Lev 3 Main and Lev 3A reservoirs did not achieved the estimated remaining recoverable resources. In this study the new 3D seismic data, production history and petrophysical data were integrated in order to relocate the unachieved residual OGIP and also to find new drilling opportunities for additional potential resources.
The Istria Depression is situated in the central part of the Romanian shelf of the Black Sea, between the Heracleea fault to the north and the offshore extension of the Peceneaga-Camena fault to the south. The analysis of the geological and structural evolution from Paleogene to Neogene was performed using wells, seismic lines, gravimetric and magnetometric data from this basin and the neighbouring geological provinces, as well as all other available information. The structural-tectonic framework of this depression is mainly represented by a series of faults and morpho-structural elements. The Depression's faults can be classified into two big categories: faults affecting the pre-Oligocene formations and faults affecting the younger formations. The pre-Oligocene faults from the southern and the northern parts of Istria Depression influenced its formation process. A few of them, such as: Sinoe, South Portita and Lebada, affect also the lower part of the Oligocene formations. The young faults influenced post-Oligocene deposits and two zones of concentration can be distinguished: an eastern one in which the faults have a NE-SW trending and a western one, with a near concentric disposition. As a conclusion thereof, the authors can affirm that the analysis of the geological and structural framework in the Istria Depression must be approached in the general context of the Black Sea, and particularly of the Romanian shelf. Throwing light upon the structural framework and related to it, upon the geological evolution of the Istria Depression, during the Paleogene-Neogene, formations that include the main source rock - the Oligocene - on the one hand, as well as some reservoir rocks - in the Eocene, Pontian and Dacian is of a very great importance both in the evaluation of the petroleum potential and related to it in the management of the exploration works. Introduction The study area lies in the western side of the Black Sea in the area of Romanian Continental Plateau, (Fig. 1). To locate it more accurately, it is worth mentioning the main structural element that is to be found in this area, namely "Euxinic Slope". "The Euxinic Slope" has been defined as a paleorelief probably generated by flexure processes of the Pre-Eocene sedimentary formations, processes that caused the fast sinking and increasing of the sedimentary cover thickness towards the deep area of the Black Sea. This paleorelief is overlaid by the Oligocene and post-Oligocene deposits, (Fig. 2), and morphologically speaking, they have the following characteristics: average dip of about 10 degrees, ranging from 5 degrees to 25 degrees; the difference in level between the shelf-break and the slope base is between 1000 and 3500 m. (Refs 1). The Euxinic Slope route (path, course, shape) across the Romanian shelf displays two main branches: the northern branch having a E-W trend, which seems to be parallel to the Heracleea fault. The Southern branch has generally NNWSSE trend, which might be the extension of Peceneaga-Camena fault.
This paper discusses the exploration potential of extensional structures in pre-Messinian formations in central Nile Delta Basin. The study aims at detailed description of extensional events and discusses the exploration potential of specific structures generated.Particularly, structural elements of pre-Messianian sequences were partially deciphered in the past, due to quality of seismic data and spare and scarce wells drilled to these levels. The newly acquired high quality 3D seismic data has been able to improve the image underneath the pre-Messinian. This has resulted in the understanding of tectonic activity, faults system and structures developed.Two extensional events characterize the tectonic activity in the Late Oligocene through Messinian. First extensional event is related to onset of Gulf of Suez rifting and generate a W-E system of basement involved faults and reactivation of syn-rift hinge zone. Related structures of this extensional phase are represented by growth anticline, drag folds and rotated blocks. The second extensional tectonic event occurred in Tortonian. The structural style corresponds to tilted and eroded fault blocks dipping to north and being aligned in a northsouth direction corresponding to the main normal faults trend.This study of the pre-Messinian extensional structures described here will have a direct impact on the exploration activities design, several important prospects being delineating among the structures developed during both extensional phases.
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