Mohamed I. Abdel-Fattah

Seismic interpretation of the Aptian Alamein Dolomite in the Razzak oil field, Western Desert, Egypt

The Razzak oil field lies in the northern part of Abu Gharadig Basin (northern part of the Western Desert). Aptian Alamein Dolomite is a reservoir rock, in which the oil is trapped in the fractures of the dolomite, depending on structural framework affecting it. The Razzak field structure is one of the most complex structures in the Western Desert of Egypt. The integration of borehole data and 3D seismic interpretation shows that the Jurassic forms a horst block separating the Razzak field into north and south Razzak fields. This horst block is bounded on the southeast by NE-SW trending normal faults (sigma fault) and on the north by several normal faults which step down into the Alamein Basin to the north. The behavior of the sigma fault gives a new concept that the migration of hydrocarbons from the south to the north direction could not be sealed by the NE-SW horst block. Time- and depth-structure maps of Alamein Dolomite illustrate different structure features that play an important role in the hydrocarbon potentialities and prospect identification in the area. One primary component of exploration and development success is to identify the faults that provide structural closure and traps. Two main faults run in the NE-SW direction and form a pattern of horst and graben blocks. In addition, NW-SW trending faults cut these blocks and form a right-lateral strike-slip component of displacement. Four- and three-way dip structural closures represent the fruitful locations for high production and new prospect wells in the Razzak oil field and other similar setting elsewhere.

Sequence stratigraphic controls on reservoir characterization and architecture: case study of the Messinian Abu Madi incised-valley fill, Egypt

Understanding sequence stratigraphy architecture in the incised-valley is a crucial step to understanding the effect of relative sea level changes on reservoir characterization and architecture. This paper presents a sequence stratigraphic framework of the incised-valley strata within the late Messinian Abu Madi Formation based on seismic and borehole data. Analysis of sand-body distribution reveals that fluvial channel sandstones in the Abu Madi Formation in the Baltim Fields, offshore Nile Delta, Egypt, are not randomly distributed but are predictable in their spatial and stratigraphic position. Elucidation of the distribution of sandstones in the Abu Madi incised-valley fill within a sequence stratigraphic framework allows a better understanding of their characterization and architecture during burial.Strata of the Abu Madi Formation are interpreted to comprise two sequences, which are the most complex stratigraphically; their deposits comprise a complex incised valley fill. The lower sequence (SQ1) consists of a thick incised valley-fill of a Lowstand Systems Tract (LST1)) overlain by a Transgressive Systems Tract (TST1) and Highstand Systems Tract (HST1). The upper sequence (SQ2) contains channel-fill and is interpreted as a LST2 which has a thin sandstone channel deposits. Above this, channel-fill sandstone and related strata with tidal influence delineates the base of TST2, which is overlain by a HST2. Gas reservoirs of the Abu Madi Formation (present-day depth ∼3552 m), the Baltim Fields, Egypt, consist of fluvial lowstand systems tract (LST) sandstones deposited in an incised valley. LST sandstones have a wide range of porosity (15 to 28%) and permeability (1 to 5080mD), which reflect both depositional facies and diagenetic controls.This work demonstrates the value of constraining and evaluating the impact of sequence stratigraphic distribution on reservoir characterization and architecture in incised-valley deposits, and thus has an important impact on reservoir quality evolution in hydrocarbon exploration in such settings.

3D Geometric Modeling of the Abu Madi Reservoirs and Its Implication on the Gas Development in Baltim Area (Offshore Nile Delta, Egypt)

3D geometric modeling has received renewed attention recently, in the context of visual scene understanding. The reservoir geometry of the Baltim fields is described by significant elements, such as thickness, depth maps, and fault planes, resulting from an interpretation based on seismic and well data. Uncertainties affect these elements throughout the entire interpretation process. They have some bearing on the geometric shape and subsequently on the gross reservoir volume (GRV) of the fields. This uncertainty on GRV also impacts volumes of hydrocarbons in place, reserves, and production profiles. Thus, the assessment of geometrical uncertainties is an essential first step in a field study for evaluation, development, and optimization purposes. Seismic data are best integrated with well and reservoir information. A 3D geometric model of the Late Messinian Abu Madi reservoirs in the time and depth domain is used to investigate the influence of the reservoir geometry on the gas entrapment. Important conceptual conclusions about the reservoir system behavior are obtained using this model. The results show that the reservoir shape influences the seismic response of the incised Abu Madi Paleovalley, making it necessary to account for 3D effects in order to obtain accurate results.

Diacritical Seismic Signatures for Complex Geological Structures: Case Studies from Shushan Basin (Egypt) and Arkoma Basin (USA)

Seismic reflection techniques show an imperative role in imaging complex geological structures and are becoming more acceptable as data interpreting tools in 2D/3D view. These subsurface geological structures provide complex seismic signature due to their geometrical behavior. Consequently, it is extremely difficult to interpret these seismic sections in terms of subsurface configuration. The main goal of this paper is to introduce seismic attributes as a powerful tool to interpret complex geological structures in different geological settings. In order to image these complex geological features, multiple seismic attributes such as coherence and curvature have been applied to the seismic data generated over the Shushan Basin (Egypt) and Arkoma Basin (USA). Each type of geological structure event usually generates a unique seismic “signature” that we can recognize and identify by using these seismic attributes. In Shushan Basin (Egypt), they provide a framework and constraint during the interpretation and can help prevent mistakes during a 3D structural modeling. In Arkoma Basin (USA), the seismic attributes results provide useful information for broader analyses of the complex structural relations in the region where the Ouachita orogenic belt intersects with the southern Oklahoma aulacogen. Finally, complex geological structures provide dramatically diacritical seismic signatures that can be easily interpreted by collaborating conventional seismic interpretation techniques with multiple seismic attributes.

Impact of depositional environment on petrophysical reservoir characteristics in Obaiyed Field, Western Desert, Egypt

Identification of the types of the depositional environments that have control or influence on the distribution of petrophysical parameters is required to assess the potential utility of these parameters in the reservoir analysis. The primary depositional facies plays an important role in the reservoir quality and assessment of the petrophysical characteristics of hydrocarbon bearing zones in exploration and development operations. Petrophysical characteristics, depositional environment, and hydrocarbon prospectivity of the Middle Jurassic Upper Safa reservoirs in the Obaiyed Field (Western Desert, Egypt) are described using data from wireline logs (gamma ray, density, neutron, sonic, and resistivity) from 14 wells. Petrophysical characteristics of Upper Safa reservoirs (unit A and unit B) change significantly with variations of depositional facies and lithology. These units are interpreted to be composed of fluvial channel sands (unit A) and tidal channel sands (unit B) based on a gamma ray curve signatures. Litho-saturation analysis, petrophysical parameters, and net pay thickness maps of the Upper Safa reservoirs show variations along the study area. The main factor controlling differences in petrophysical properties and thickness for these reservoirs is the type of sandstone facies. Shales cause a major reduction in the porosity and gas saturation of the reservoir sandstones especially in the unit B reservoir which has dispersed and laminated shale and low resistivity net pay zone. The best reservoir characteristics belong to the unit A, which has high effective porosity (PHIE), low shale content (Vsh), and high gas saturation (Sg). Maps of reservoir parameters based on precise understanding of its depositional environment indicate the location of possible sites for future gas development activities in the Obaiyed Field.