Characterizing complex slope channel reservoirs applying extended elastic impedance, Saffron gas field, offshore Nile Delta, Egypt

2021 ◽  
Vol 40 (2) ◽  
pp. 151a1-151a7
Author(s):  
Adel Othman ◽  
Ahmed Ali ◽  
Mohamed Fathi ◽  
Farouk Metwally
Keyword(s):  
Water Saturation ◽  
Nile Delta ◽  
Seismic Attributes ◽  
Significant Degree ◽  
Seismic Inversion ◽  
Gas Field ◽  
Amplitude Variation With Offset ◽  
3D Volume ◽  
Elastic Impedance ◽  
Sand Bodies

In a complex reservoir with a significant degree of heterogeneity, it is a challenge to characterize the reservoir using different seismic attributes based on available data within certain time constraints. Prestack seismic inversion and amplitude variation with offset are among the techniques that give excellent results, particularly for gas-bearing clastic reservoir delineation because of the remarkable contrast between the latter and the surrounding rocks. Challenges arise when a shortage of seismic or well data presents an obstacle in applying these techniques. A further challenge arises if it is necessary to predict water saturation (Sw) using the seismic data because of the independent nonlinear relationship between Sw and seismic attributes and inversion products. Prediction of Sw is necessary not only for characterizing pay from nonpay reservoirs but also for economic reasons. Therefore, extended elastic impedance has been performed to produce a 3D volume of Sw over the reservoir interval. Then, a 3D sweetness volume and spectral decomposition volumes were used to grasp the geometry of the sand bodies that have been charged with gas in addition to their connectivity. This could help illustrate the different stages in the evolution of the Saffron channel system and the sand bodies distribution, both vertically and spatially, and consequently increase production and decrease development risk.

Application of geostatistical seismic inversion in reservoir characterization of Sapphire gas field, offshore Nile Delta, Egypt

2019 ◽  
Vol 38 (6) ◽  
pp. 474-479
Author(s):  
Mohamed G. El-Behiry ◽  
Said M. Dahroug ◽  
Mohamed Elattar
Keyword(s):  
Reservoir Characterization ◽  
Nile Delta ◽  
Seismic Inversion ◽  
Reservoir Modeling ◽  
Connectivity Analysis ◽  
Gas Field ◽  
Geostatistical Inversion ◽  
Well Data ◽  
Reservoir Connectivity ◽  
Inversion Techniques

Seismic reservoir characterization becomes challenging when reservoir thickness goes beyond the limits of seismic resolution. Geostatistical inversion techniques are being considered to overcome the resolution limitations of conventional inversion methods and to provide an intuitive understanding of subsurface uncertainty. Geostatistical inversion was applied on a highly compartmentalized area of Sapphire gas field, offshore Nile Delta, Egypt, with the aim of understanding the distribution of thin sands and their impact on reservoir connectivity. The integration of high-resolution well data with seismic partial-angle-stack volumes into geostatistical inversion has resulted in multiple elastic property realizations at the desired resolution. The multitude of inverted elastic properties are analyzed to improve reservoir characterization and reflect the inversion nonuniqueness. These property realizations are then classified into facies probability cubes and ranked based on pay sand volumes to quantify the volumetric uncertainty in static reservoir modeling. Stochastic connectivity analysis was also applied on facies models to assess the possible connected volumes. Sand connectivity analysis showed that the connected pay sand volume derived from the posterior mean of property realizations, which is analogous to deterministic inversion, is much smaller than the volumes generated by any high-frequency realization. This observation supports the role of thin interbed reservoirs in facilitating connectivity between the main sand units.

scholarly journals Formation evaluation and reservoir characteristics of the Messinian Abu Madi sandstones in Faraskour Gas Field, onshore Nile Delta, Egypt

2020 ◽  
Author(s):  
Mahmoud Leila ◽  
Ali Eslam ◽  
Asmaa Abu El-Magd ◽  
Lobna Alwaan ◽  
Ahmed Elgendy
Keyword(s):  
Water Saturation ◽  
Nile Delta ◽  
Hydrocarbon Exploration ◽  
The Other ◽  
Reservoir Rock ◽  
Reservoir Quality ◽  
Pore System ◽  
Reservoir Properties ◽  
Gas Field ◽  
Irreducible Water Saturation

Abstract The Messinian Abu Madi Formation represents the most prospective reservoir target in the Nile Delta. Hydrocarbon exploration endeavors in Nile Delta over the last few decades highlighted some uncertainties related to the predictability and distribution of the Abu Madi best reservoir quality facies. Therefore, this study aims at delineating the factors controlling the petrophysical heterogeneity of the Abu Madi reservoir facies in Faraskour Field, northeastern onshore part of the Nile Delta. This work provides the very first investigation on the reservoir properties of Abu Madi succession outside the main canyon system. In the study area, Abu Madi reservoir is subdivided into two sandstone units (lower fluvial and upper estuarine). Compositionally, quartzose sandstones (quartz > 65%) are more common in the fluvial unit, whereas the estuarine sandstones are often argillaceous (clays > 15%) and glauconitic (glauconite > 10%). The sandstones were classified into four reservoir rock types (RRTI, RRTII, RRTIII, and RRTIV) having different petrophysical characteristics and fluid flow properties. RRTI hosts the quartzose sandstones characterized by mega pore spaces (R35 > 45 µm) and a very well-connected, isotropic pore system. On the other side, RRTIV constitutes the lowest reservoir quality argillaceous sandstones containing meso- and micro-sized pores (R35 > 5 µm) and a pore system dominated by dead ends. Irreducible water saturation increases steadily from RRTI (Swir ~ 5%) to RRTIV (Swir > 20%). Additionally, the gas–water two-phase co-flowing characteristics decrease significantly from RRTI to RRTIV facies. The gaseous hydrocarbons will be able to flow in RRTI facies even at water saturation values exceeding 90%. On the other side, the gas will not be able to displace water in RRTIV sandstones even at water saturation values as low as 40%. Similarly, the influence of confining pressure on porosity and permeability destruction significantly increases from RRTI to RRTIV. Accordingly, RRTI facies are the best reservoir targets and have high potentiality for primary porosity preservation.

Characterizing complex slope channel reservoirs applying Extended Elastic Impedance, Saffron gas field, offshore Nile Delta, Egypt

2020 ◽  
Author(s):  
Adel A. A. Othman ◽  
Farouk Ibrahim Metwally ◽  
Mohamed F. M. Ali ◽  
Ahmed Saied Ali
Keyword(s):  
Nile Delta ◽  
Gas Field ◽  
Elastic Impedance ◽  
Slope Channel

Distinguishing gas-bearing sandstone reservoirs within mixed siliciclastic-carbonate sequences using extended elastic impedance: Nile Delta — Egypt

2016 ◽  
Vol 4 (4) ◽  
pp. T427-T441 ◽  
Author(s):  
Ahmed Hafez ◽  
John P. Castagna
Keyword(s):  
Nile Delta ◽  
Rock Physics ◽  
Seismic Inversion ◽  
Anomalous Behavior ◽  
Well Logs ◽  
High Impedance ◽  
Bright Spots ◽  
Fluid Properties ◽  
Elastic Impedance ◽  
Gas Bearing

In the Abu Madi Formation of the Nile Delta Basin, false bright spots may be misinterpreted as being indicative of hydrocarbons due to mixed clastics and carbonates. However, rock-physics analysis of well logs in a particular prospect area where such ambiguity exists suggests that attributes derived using extended elastic impedance (EEI) inversion may help identify hydrocarbons because they better show anomalous behavior in particular directions that are readily related to pore fluids and lithology. The EEI attributes calculated from well logs correlate extremely well to lithology and fluid properties, thereby differentiating amplitude anomalies caused by gas-bearing sandstones encased in shale from similar amplitudes caused by juxtaposition of high-impedance carbonates over lower impedance water-filled sandstones. Comparing seismically derived EEI attributes to well logs from a productive well and a nonproductive well indicates that seismic inversion can successfully identify lithologies such as shales, sandstones, carbonates, and anhydrite and distinguish gas-bearing from water-bearing sandstones. The technique can thus potentially be used to better delineate and risk prospects in the area, as well as assisting exploration efforts in other locations where similar ambiguities in amplitude interpretation exist.

SEISMIC TO SIMULATION: INTEGRATED RESERVOIR MODEL FOR THE PATRICIA BALEEN GAS FIELD

2002 ◽  
Vol 42 (1) ◽  
pp. 83
Author(s):  
P. Fink ◽  
M. Adamson ◽  
F. Jamal ◽  
C. Stark
Keyword(s):  
Water Saturation ◽  
Subsequent Development ◽  
Seismic Survey ◽  
3D Seismic ◽  
Reservoir Model ◽  
Gas Field ◽  
Facies Model ◽  
Time Migration ◽  
Gas Fields ◽  
Elastic Impedance

The Patricia and Baleen offshore gas fields are located in the northeastern part of the Gippsland Basin in southeast Australia. Although discovered by two exploration wells almost a quarter of a century ago, the two gas fields only recently have again become the focus of appraisal and subsequent development activity through OMV’s acquisition of Cultus in 1999.After the drilling of a successful appraisal well in late 1999, a high resolution 3D seismic survey was acquired in early 2000. No further data acquisition will be undertaken. Special emphasis was therefore put on maximising the value of the 3D dataset by integrating the PreSTM (Pre. Stack Time Migration) seismic and several Elastic Impedance attributes with all other available subsurface data prior to building a sophisticated stochastic reservoir model for simulation.This paper describes how the integration of leading edge seismic technology with unconventional geological modelling was used to overcome a number of major challenges in order to build a coherent static reservoir model and constrain resource uncertainty given the limited amount of wireline and core data:A large proportion of the gas fields is strongly affected by seismic tuning which would introduce significant uncertainties on GRV and GWC estimations from seismic, if not accounted for properly. Likewise all seismic and to a somewhat lesser extent basic inversion based attributes used for reservoir property determination are strongly affected by this geophysical artefact: These challenges (and seismic pitfalls) were met by inverting the conventional 3D seismic for Pand S- wave impedances and generating a set of Elastic Impedance Cubes, difference cubes and LRM Cubes (standing for the elastic constants Lambda (λ), Rho (ρ) and Mhu (μ)), defining petroacoustic properties of the reservoir rocks. These cubes were tested for mathematical dependency and used for the conditioning of the facies and porosity models.The glauconitic Gurnard reservoir contains a high fraction of conductive minerals and is almost completely bioturbated. Conventional saturation estimations based on wireline-logs and conventional sequence stratigraphic facies description did not deliver a reliable picture: Instead a facies model based on ichnofabric analysis was built and constrained with data available at the three well locations. Saturation height functions were applied separately for each facies type. The Rho-Lambda (ρλ) cube was used to condition facies distribution away from the wells.More specifically, the results presented in the paper are:Elastic Impedance inversion provided vertical seismic resolution in the order of 4 m to 10 m, thereby allowing a more accurate seismic estimation of GRV and the GWC. Lamesf Constants were extracted from seismic in order to classify lithology.A realistic facies model was built utilizing the Rho- Lambda (ρλ) cube combined with ichnofabric analysis tied to permeability and water saturation distributions.Elastic Impedance Difference cubes were successfully calculated to eliminate tuning even further and condition the stochastic porosity model.Connected volume maps were used to optimise the production well pathsThe GIIP upside volume has been upgraded compared to that based on an earlier simplistic geological reservoir model used for simulation. A more realistic P10/P90 reserves range is now supported by a number of deterministic and stochastic reservoir models.

scholarly journals Extended Elastic Impedance Inversion for Better Delineation of Gasbearing Sand Reservoir, Saffron Gas Field, Offshore Nile Delta, Egypt

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Othman AAA ◽  
◽  
Ali MFM ◽  
Metwally FI ◽  
Ali AS ◽  
...  
Keyword(s):  
Seismic Data ◽  
Nile Delta ◽  
Petrophysical Properties ◽  
Gas Field ◽  
Fluid Content ◽  
Impedance Inversion ◽  
Gradient Domain ◽  
The Difference ◽  
Elastic Impedance ◽  
Seismic Anomaly

Extended Elastic Impedance (EEI) is a very useful seismic reconnaissance attribute. EEI logs can directly correspond to the petrophysical properties of the reservoir and the seismic. EEI reflectivity volumes can be obtained directly from the pre-stack seismic data. Better discrimination between the seismic anomaly caused by either lithology or fluid content can be utilized by applying this approach. The concept of extended elastic impedance is used to derive the petrophysical properties and distribute the reservoir facies. The study area was a Pliocene gas field, that lies in the deep marine, Offshore Nile Delta, Egypt. The workflow is simple, efficient, and uses very few inputs. We started with the fluid/ lithology logs and investigated the optimum projection in the intercept/gradient domain. Then, we used the conditioned angle stacks, to calculate the intercept/ gradient volumes, using Shuey’s two-term Approximation. The intercept and gradient volumes are converted directly to the fluid and lithology 3D volumes, without any of the pre-stack inversion constraints. The outputs were tested using a blind well and the correlation exceeds 80%. The results show that the EEI is a worthy effort to highlight the difference between the reservoir and nonreservoir sections, to identify the hydrocarbon area.

Deepwater reservoir heterogeneity delineation using rock physics and extended elastic impedance inversion: Nile Delta case study

2014 ◽  
Vol 2 (4) ◽  
pp. T205-T219 ◽  
Author(s):  
Ahmed Hafez ◽  
Folkert Majoor ◽  
John P. Castagna
Keyword(s):  
Nile Delta ◽  
Rock Physics ◽  
Amplitude Variation ◽  
Amplitude Variation With Offset ◽  
Impedance Inversion ◽  
Net To Gross ◽  
Deepwater Channel ◽  
Static Connectivity ◽  
Elastic Impedance

Deepwater channel reservoirs in the Nile Delta are delineated using extended elastic impedance inversion (EEI). We used the following workflow: seismic spectral blueing, rock physics and amplitude variation with offset modeling, seismic EEI and interpretation of the inverted cubes in terms of geologic facies, net-to-gross ratio, and static connectivity among depositional geobodies. Three subenvironments within the targeted reservoir interval were recognized using a combination of shale volume and [Formula: see text]-inverted cubes. These were used to generate 3D geobodies and a net-pay thickness map that were used in turn to calculate reservoir volumetrics. The results from the workflow matched well logs and could thus be used to investigate the potential of nearby prospects that have the same geologic settings.

scholarly journals INTEGRATED AVO, ELASTIC SEISMIC INVERSION AND PETROPHYSICAL ANALYSIS FOR RESERVOIR CHARACTERIZATION: A CASE STUDY OF GAS FIELD, SOUTH SUMATERA BASIN

2018 ◽  
Vol 3 (1) ◽  
pp. 7-14
Author(s):  
Abdul Haris ◽  
Ressy Sandrina ◽  
Agus Riyanto
Keyword(s):  
Water Saturation ◽  
Seismic Inversion ◽  
Elastic Parameter ◽  
Well Log ◽  
Gas Field ◽  
Log Data ◽  
Petrophysical Analysis ◽  
Avo Analysis ◽  
Shale Volume

Integrated Amplitude Versus Offset ( AVO), elastic seismic inversion and petrophysical analysis have been successfully applied to estimate the elastic parameters of the reservoir for a case study of the gas field in south Sumatera basin. This paper aims to have better understanding the petrophysical properties of the reservoir. The petrophysical analysis was carried out by performing routine formation evaluation that includes calculation of shale volume, porosity, and water saturation of basic well log data. Sensitivity analysis was conducted to evaluate the sensitivity parameters of the log for changing in lithology, porosity, and fluid content in the reservoir. For completing the availability of elastic parameter from well log data, shear wave logs were derived from Castagna’s mudrock line relationship. Further, P-impedance, S-impedance, VpVs ratio, LambdaRho (λρ), MuRho (μρ) and density(ρ) were then calculated through a Lambda-Mu-Rho (LMR) transformation. Prior to performing AVO analysis and elastic seismic inversion, super gather technique was applied to improve the reliability of pre-stack seismic data. Elastic seismic inversion was carried out to extract the lateral elastic properties to capture lithology and fluid changes in the reservoir. In addition, AVO analysis of pre-stacked data was applied to identify hydrocarbon-bearing sandstone at target zone. The petrophysical analysis shows that porosity versus density crossplot is able to distinguish sand-shale based on 34% shale volume cutoff, while LMR crossplot is able to delineate hydrocarbon zone at water saturation value under 65%. The predicted lateral elastic parameter shows slightly higher value compare to overlying layer.

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