West Delta Deep Marine Concession Research Articles

Biomarker and isotopic characteristics of Miocene condensates and natural gases, West Delta deep marine concession, Eastern Mediterranean, Egypt

The Western Delta Deep Marine Concession (WDDM) in the Eastern Mediterranean Sea is one of northern Africa's most recent petroleum-potential regions for gas and condensate exploration. The present study aims to determine the characteristics of the 15 natural gases and 5 associated condensate samples, using molecular compositions and isotopes from the Miocene reservoir rocks in the various wells located in the WDDM. The results of this study are also used to determine the gas-condensate correlation for their probable source rocks as well as the methane-generating mechanisms (i.e., thermogenic or microbiological). Results highlighted in this research reveal that most of the natural gases in WDDM are mainly thermogenic methane gases, with small contributions of biogenic methane gases that were generated from mainly mixed sources, with a high sapropelic organic matter input for biogenic gases. The thermogenic methane gases were formed from secondary oil and oil/gas cracking at the high maturity stage of the gas window. The biogenic gases are also contributed to the Miocene reservoirs, which are formed from the primary cracking of kerogen at low maturity stage by the action of CO2 bacterial reduction. In addition, the saturated and aromatic biomarker results show that the condensate samples were generated from clay-rich source rocks. This source unit of the Miocene condensates were deposited in a fluvial deltaic environmental setting, containing mixed kerogen type II/III and accumulated during the Jurassic–Cretaceous, as evidenced by the age dating indicators. The properties of the natural gases and associated condensates in the Miocene reservoir rocks suggest that most of the thermogenic methane gases, together with the condensate, are derived primarily from mature Jurassic–Cretaceous source rocks and formed by secondary oil and oil/gas cracking at the gas generation window, as demonstrated by the 1-D basin modelling results highlighted in the prior works. Therefore, most of the natural gases in WDDM are non-indigenous and migrated from more mature Jurassic–Cretaceous source rocks in the nearby Northern Sinai provinces or the deeper sequences in the offshore Nile Delta provinces.

Petrophysical and Rock Physics Analysis Using Well Log Data for Gas Detection in Scarab Gas Field, West Delta Deep Marine Concession, Egypt

Petrophysical and Rock Physics Analysis Using Well Log Data for Gas Detection in Scarab Gas Field, West Delta Deep Marine Concession, Egypt

Rock physics analysis from predicted Poisson's ratio using RVFL based on Wild Geese Algorithm in scarab gas field in WDDM concession, Egypt

Some of the important rock physics parameters, such as the shear-wave velocity and Poisson's ratio, are conventionally calculated from compressional and shear sonic well logs. Although these parameters are vital for geomechanical purposes, these types of shear sonic logs are rarely recorded for most wells. Therefore, this study aims to use ordinary well log and seismic data to predict the Poisson's ratio using some of the machine learning algorithms that are based on a proposed model calculated from a modified version of the Random Vector Functional Link (RVFL) using the Wild Geese Algorithm (WGA). This is applied as a case study in the Scarab gas field in the West Delta Deep Marine (WDDM) concession, Egypt. The main aim of using WGA is to determine the best configuration from the parameters of RVFL to enhance the process of prediction. The rock physics templates are used for interpreting the lithology and pore-fluid from well log data and RVFL-WGA. This is achieved using the cross-plot of P-impedance versus Poisson's ratio, Lambda-Rho versus Mu-Rho, Poisson's ratio versus bulk modulus and P-impedance versus Vp/Vs ratio from both methods. All cross plots are color-coded by the shale volume and hydrocarbon saturation.

Integration of well logs and seismic data for facies analysis and modelling of the El-Wastani Formation in the Sequoia Gas Field, offshore Nile Delta, Egypt

Reservoir rock facies modelling helps in determining the degree of reservoir variability for enhanced management of the heterologous facies’ reservoirs, both at borehole scale and more regionally at seismic scale. The Pliocene Offshore Sequoia Gas Field is located near the boundary between the Rosetta Concession and the West Delta Deep Marine Concession (WDDM) on the western side of the Nile Delta. It is characterised by canyon systems of complex turbidite channel-levee deposits that are multi-stacked. In order to create various depositional facies that are compatible with a deep marine environment, an advanced facies model was built from the combination of the seismic, core, and formation micro imager (FMI). Sandstones (laminated and massive), shale (laminated and massive mud-rock), silt, and thin sandstone beds were identified as four major facies. In the Sequoia field area, the El-Wastani Formation is known as a heterogeneous sequence of sandstones and mudstones arranged into a broad upward-fining succession. High-quality, blocky sands exist at the base, while the upper portion is characterised primarily by isolated sand bodies intercalated with mudstones in the presence of some thin-bedded sands (their thickness less than 1 m).

A new deeper channel system predicted using seismic attributes in scarab gas field, west delta deep marine concession, Egypt

The west Delta deep marine (WDDM) concession is one of the most gas-producing provinces in Egypt, due to its widely distributed channel systems. This paper aims to illustrate the role of seismic attributes analysis to improve tracing of subtle stratigraphic features, such as shallow fluvial channel systems. The study is carried out in Scarab gas field, located in the WDDM area, which embodies deep marine slope channels. Two vertically overlapped channels, channel-1 and channel-2 (of Pliocene age), are considered the chief channels constituting reservoirs of this area. The methodology implemented here is to analyze the available seismic data volume, using the spectral decomposition and root mean square (RMS) attributes, to highlight the occurrence and extension of channel features on the stratigraphic surface of interest and within a certain time interval slice. These subtle features are difficult to investigate using traditional amplitude seismic data. The use of spectral decomposition tool and root mean square attribute is proved to help identify and highlight the channels and bright spot features, which indicate the gas accumulation. In addition, faults are easily recognized using these attributes. Below the total depths of the present wells, a new deeper channel is expected to be apparent below channel-2 (below the total depths of wells Dc) and to the west of channel-16 at the time slice −2460 ms (about −2035 m depth). The major part of this channel is meandering and trends from south to north where it is wider to the north forming an area of a bright spot. This channel may be filled with gas-prone sand, as deduced by the used seismic attributes. This expectation is proposed depending on the high similarity between the characteristics of the used seismic attributes of the drilled channels (1 and 2) and that of the anticipated ones. More detailed studies and drilling to a depth of approximately −2000 m at a proposed well, located about 1 km to the north of well Dc, are recommended for exploration of the detected channel.

Integrated seismic and well gamma-ray analysis for delineation Sienna channel depositional architecture, offshore West Nile Delta, Egypt

ABSTRACT The Nile Delta gas reservoirs are dominated by Plio-Pleistocene and Miocene channel deposits which became nowadays the key player for gas production in Egypt. These channelized features are spectacularly imaged on high-quality seismic data, this paper deals with channel geomorphology imaging using different geophysical and geological tools for better under-standing its architecture and fairway delineation in Sienna field also delineating some reasons for reservoir compartmentalization in the studied area which acts as an analogue for the marine slope channels in Pliocene reservoirs within West Delta deep marine concession (WDDM).Seismic attributes were used like Root Mean Square (RMS) amplitude extraction, Ant tracking and Spectral decomposition and finally pre-stack seismic inversion products. By correlating seismic signature with wells log data, four depositional cycles in the Sienna channel were identified which are stacked upon each other in Sienna canyon. The reason for Sienna system compartmentalization maybe not only effect by faults density but also facies quality which is changes from well to another as a result of distal deposits of turbidity slope channels. The location of new wells could be more precisely delineated for further reservoir development in Sienna channels.

Sequoia reservoir evaluation through conventional petrophysical analysis in Eastern Mediterranean, Nile Delta, Egypt

ABSTRACT The Sequoia Field, in West Delta Deep Marine concession, represents deep marine slope channels in Nile Delta of Egypt. The main hydrocarbon bearing formation is the Late Pliocene El Wastani Formation. Sequoia Channel of the El Wastani Formation are considered as the main reservoirs of Sequoia Field. Well log data analysis, of five wells were accomplished using computer software programs (e.g. Interactive petrophysics (I.P.) Software was used in petrophysical evaluation for Petrophysical analysis, in terms of determining the effective porosity, shale volume, and reservoir fluid saturation of Sequoia Channel of El Wastani Formation, is the primary aim of this study in order to achieve better determination of the reservoir quality in Sequoia Field. We found that Sequoia Channel of El Wastani Formation is having high storage capacity properties permit them of bearing a good amount of hydrocarbon fluids in the Sequoia Field. It was found that effective porosity ranges between 19% and 29%, shale content ranges between 10% and 28%, the water saturation ranges between 15% and 40%. It is clear that the facies effect is the main factor that is controlling the distribution of the petrophysical properties.

Reservoir quality determination through petrophysical analysis of El Wastani Formation in Scarab Field, Offshore Nile Delta, Egypt

The Scarab Field, in West Delta Deep Marine concession, represents deep marine slope channels in Nile Delta of Egypt. The main hydrocarbon bearing formation is the Late Pliocene El Wastani Formation. Channel-1 and channel-2 of the El Wastani Formation are considered as the main reservoirs of Scarab Field. Well log data analysis, of four wells were accomplished using computer software programs (e.g. Interactive petrophysics (I.P. V. 3.6) software was used in petrophysical evaluation Petrophysical analysis, in terms of determining the effective porosity, shale volume, and reservoir fluid saturation of Channel-1 and channel-2 of El Wastani Formation, is the primary aim of this study in order to achieve better determination of the reservoir quality in Scarab Field. We found that Channel-1 and channel-2 of El Wastani Formation are having high storage capacity properties permit them of bearing a considerable amount of hydrocarbon fluids in the Scarab Field. It was found that effective porosity in chaneel-1 ranges between 18% and 30%, shale content ranges between 20% and 30%, the water saturation ranges between 36% and 52% in channel -2 the effective porosity ranges between 22% and 25%, shale content ranges between 20% and 30%, the water saturation ranges between 40% and 52.5% It is clear that the facies effect is the main factor that is controlling the distribution of the petrophysical properties.

Unlocking gas reserves in bypassed stratigraphic traps in a deepwater brownfield using prestack seismic inversion: A case study from offshore Nile Delta, Egypt

In deepwater depositional systems such as the slope canyon-turbidite channel system encountered on the continental slope of the offshore West Nile Delta Basin, deterministic prestack seismic inversion followed by facies classification using formation microimager facies logs delineated thick-bedded and thin-bedded gas-sand reservoirs encased in bypassed stratigraphic traps. Prestack seismic inversion was applied over the Scarab Field in the West Delta Deep Marine concession to evaluate the hydrocarbon potential of newly identified stratigraphic traps. Three angle stacks were inverted using a simultaneous inversion approach to estimate the elastic properties (P-impedance and VP/VS ratio). Using the elastic volumes produced from the inversion, Bayesian facies classification was applied to separate thin- and thick-bedded gas-sand facies from shale. Facies classification was focused on two prospective bypassed stratigraphic traps: the Upper Scarab Channel remnant levees (remnant middle levee [RML] and southern remnant levee) and the Lower Scarab Channel lateral accretion packages (LAPs). A development well location is proposed to validate the interpreted gas-sand reservoirs in the shallower RML and the deeper LAPs stratigraphic traps. The results suggest that application of the prestack seismic inversion and facies classification led to reliable inferences likely to have a positive impact on field development, potential reserves growth, and consequently boosting gas production.

Reducing the risk of hydrocarbon exploration and lithology characterization — using a neural network approach in the West Delta Deep Marine Concession Area, Offshore Nile Delta, Egypt

There are many approaches and concepts for the exploration and development of hydrocarbon reservoirs. In this study, we develop both a lithology classification and a gas chimney prediction workflow. We classify the entire seismic volume into its most likely facies domains and transform the seismic cube into a gas chimney probability cube. Both these approaches utilize a neural network algorithm, which we find is an efficient method to integrate the multiple input attributes required to extract the target log, or to isolate target features from the seismic background data. A combination of a set of seismic attributes (obtained from multilinear regression) with the nonlinearity of the artificial neural network technique is used to develop effective workflows to classify and explore the reservoirs. Analysis of the results helps to quantify the chance of success of the exploration prospects and also, in conjunction with the petroleum system of the prospects, leads to a reduced risk of the hydrocarbon exploration and development wells.

Reservoir characterization using fluid substitution and inversion methods, offshore West Nile Delta, Egypt

Sinbad channel lies in West Delta Deep Marine Concession (WDDM) offshore Nile Delta, Egypt. The southern part of the channel has been penetrated by an exploratory well (Sinbad-1), but the well encountered a residual gas. The study is dedicated to assess the gas saturation in the northern extension of the channel using the advanced rock physics methods and seismic inversion techniques.Rock physics models play a crucial role in seismic reservoir characterization studies. The Fluid substitution method is the most commonly used technique using the application of Gassmann’s equation.Post-stack and Pre-stack seismic inversion have been done over the area, utilizing the seismic data set along with the well log data to better understand the lithology and fluid distribution in the channel.The main goal of the paper is to estimate the saturation of the gas at the eastern part so, after applying the previous methods at study area the eastern part of Sinbad area is having the same response of amplitude like the drilled area so we can conclude that the area has gas but we can’t know if it is economic or residual.

Reservoir architecture of deep marine slope channel, Scarab field, offshore Nile Delta, Egypt: Application of reservoir characterization

Scarab field is an analog for the deep marine slope channels in Nile Delta of Egypt. It is one of the Pliocene reservoirs in West delta deep marine concession. Channel-1 and channel-2 are considered as main channels of Scarab field. FMI log is used for facies classification and description of the channel subsequences. Core data analysis is integrated with FMI to confirm the lithologic response and used as well for describing the reservoir with high resolution. A detailed description of four wells penetrated through both channels lead to define channel sequences. Some of these sequences are widely extended within the field under study exhibiting a good correlation between the wells. Other sequences were of local distribution. Lithologic sequences are characterized mainly by fining upward in Vshale logs. The repetition of these sequences reflects the stacking pattern and high heterogeneity of the sandstone reservoir. It also refers to the sea level fluctuation which has a direct influence to the facies change. In terms of integration of the previously described sequences with a high resolution seismic data a depositional model has been established. The model defines different stages of the channel using Scarab-2 well as an ideal analog.

Prestack seismic inversion versus neural-network analysis: A case study in the Scarab field offshore Nile Delta, Egypt

In clastic depositional systems such as those encountered in the Nile Delta Basin, simultaneous prestack seismic-amplitude inversion is an effective method for detecting and appraising gas-bearing sandstone reservoirs. However, the method has limitations concerning the requirement of a reliable set of wavelets, suitable wireline logs, and a sufficiently dense initial model. The neural-network analysis method is an alternative technique which sometimes can provide similar or better results and does not require significant volumes of data. Simultaneous prestack inversion was applied over the Scarab field, West Delta Deep Marine concession, offshore Egypt. The field comprises submarine channel-based gas reservoirs that extend laterally over 20 km2. Six wells were analyzed in a rock-physics study prior to performing inversion. Three angle gathers (near: 0–15°; mid: 15–30°; far: 30–45°) were inverted for P-wave impedance (ZP), S-wave impedance (ZS), P-wave velocity (VP), S-wave velocity (VS), VP/VS, and density (ρ) using the prestack inversion method. Neural-network analysis was performed using full-stack seismic data along with well logs in the training stage, followed by cross-validation of results and rendering of VP, VS, VP/VS, and density volumes. The VP/VS volumes produced from the two methods were used to infer water saturation (Sw). Direct comparisons were made between neural-network and prestack inversion results at a blind-well location to assess the relative quality of each method. Results suggest that application of the proposed neural-network method leads to reliable inferences. Hence, using the neural-network method alone or along with the prestack inversion method has a positive impact on reserves growth and increased production.

Foraminiferal biostratigraphy of the Pliocene–Pleistocene deep marine offshore, north Nile Delta, Egypt

A high resolution biostratigraphic analysis of the Pliocene–Pleistocene sequence of the offshore Nile Delta region in West Delta Deep Marine Concession (WDDM), in which 29 planktonic foraminiferal species belonging to 8 genera and 51 benthic foraminiferal species belonging to 40 genera were identified, allowed the recognition of seven foraminiferal zones and two subzones. These are as follows: Sphaeroidinellopsis Acme Zone (MPl1), Globorotalia margaritae Zone (MPl2), Globorotalia puncticulata / Globorotalia margaritae Zone (MPl3), Sphaeroidinellopsis s.l. Zone (MPl4), Globorotalia puncticulata Subzone (MPl4a), Globorotalia planispira Subzone (MPl4b), Globigerinoides elongatus Zone (MPl5), Globorotalia inflata Zone (MPl6) and Hyalinea balthica Zone.

An example study using conventional 3D seismic data to delineate shallow gas drilling hazards from the West Delta Deep Marine Concession, offshore Nile Delta, Egypt

This paper details a study that was completed at the end of 1999 to investigate the suitability of using existing, high quality, conventionally processed 3D seismic data (hereafter 3D data) to replace specifically commissioned 2D seismic site survey data (hereafter 2D site data). For this study, three wells from an existing dataset of six in the West Delta Deep Marine Concession, offshore Egypt (WDDM) were investigated. A prescriptive workflow was developed using the 3D data and the results compared to those obtained from a conventional previously commissioned 2D digital site survey dataset. For this dataset from WDDM, the results obtained from the 3D data and the 2D data were similar, the main difference being that more numerous, smaller probable hazards were prognosed by the 3D data. After undertaking this investigation and following an independent review of the results, a recommendation was made to operate the 2000 WDDM drilling campaign using hazard prognosis from the conventional 3D data, i.e. not to acquire well-specific, new digital site surveys. This recommendation was followed and five exploration wells were drilled in 2000 with no specific, digital site survey data being acquired.No safety, operational or environmental implications were encountered as a result of this replacement and significant operational savings accrued to the operating partnership.