The goal of this research is to carry out a subsurface and petrophysical investigation to estimate the petroleum potential of the Bahariya reservoir in the Nader Field of the Khalda Ridge concession in Egypt's northwestern desert. This study depends on using the composite logs for four wells, Nader-1, Nader-2, Nader-4, and Nader-8, and twenty (2D) seismic lines. The Bahariya Formation unconformably underlies and overlies the Abu Roash and Kharita formations, respectively. The Upper and Lower Bahariya formations were evaluated as the petroleum sandstone reservoirs in the studied field. Seismic interpretations were used to clarify the structural settings on the tops of these formations. These formations' time-and-depth-structure maps reveal a variety of structural features which aid in prospect identification and hydrocarbon potential in the area. The petrophysical evaluation involves lithology identification, reservoir pressure measurements, and determinations of petrophysical parameters such as effective porosity (PHIE), net-pay thickness, water saturation (Sw), shale content (Vsh), and hydrocarbon saturation (Sh). The results of this study revealed three new proposed locations to the southeast and north of the investigated Nader field. These locations are located on appropriate structures and on four- or three-way dip structural closures that are suitable for petroleum accumulations. They also have a decrease in Vsh and Sw, and an increase in net pay, PHIE, and Sh for the Upper and Lower Bahariya reservoirs. As a result, it is advised to concentrate exploration efforts on new promising locations for more economical petroleum discoveries.
Research Article
A New hydrocarbon Prospect Determination Through Seismic Interpretation and Petrophysical Evaluation of Bahariya Reservoir in Nader field, North Western Desert, Egypt
https://doi.org/10.21203/rs.3.rs-1859565/v1
This work is licensed under a CC BY 4.0 License
Version 1
posted
You are reading this latest preprint version
Nader field
Petrophysical evaluation
Seismic interpretation
Bahariya reservoir
Prospect evaluation
Khalda ridge concession
Egypt's western desert province remains among the most promising gas and oil producing areas (Meshref 1982; Metwalli and Pigott 2005, Fagelnour et al. 2018; Metwalli et al. 2021). The study area is Nader field, which is placed in the north of Egypt's western desert with latitudes of 30° 32' 2" and 30° 35' 34.9" N, and longitudes of 26° 53' 48.5" and 26° 59' 33.5" E (Fig. 1). It is placed in the eastern part of the Shushan basin in the northwestern desert. Shushan Basin, a NE-SW trending basin and accounts for nearly a third of Egypt’s hydrocarbon production (Said 1962; EGPC 1992; Schlumberger 1995; Younes 2005). The Shushan basin has been subsiding due to the opening of Neo-Tethys since the Upper Jurassic-Lower Cretaceous (Alsharhan and Abd El-Gawad 2008). Many authors have studied the Upper and Lower Bahariya formations petrophysically, including Abu Shady et al. (2010); Aboelhassan (2017); Abdelmaksoud et al. (2019); Farrag et al. (2021); Sarhan (2021). They found that the Bahariya Formation has excellent capability as a reservoir. The Lower Bahariya Member was classified as a moderate-to-good reservoir. The aim of this investigation is to assess the hydrocarbon potential of the Upper and Lower Bahariya reservoirs in the Nader field. The study aims to integrate all the available subsurface geological and geophysical data in order to delineate new prospects in the Nader field.
Shushan, Alamine, Matruh, Khalda, and Qattara are five sub-basins in the northwestern desert (Fig. 2) (Metwalli et al. 2018). According to Sultan and Halim (1988), the NE-SW Shushan sub-basin is bordered by the Um-barka in the north and by the North Qattara Ridge in the south. The study area (Shushan sub-basin) is a major basin that formed because of the opening of the Neo-Tethys Ocean to the north in the Late Jurassic and Early Cretaceous periods. It was still a depocenter for the majority of the Cretaceous epoch (Metwalli and Pigott 2005). Like all basins in northwestern desert, it is structurally controlled by a thick sedimentary section and belongs to the unstable Shelf regime (Said 1962). The study area is affected by normal faults related to the Cretaceous time with NW-SE trend. The stratigraphy and tectonic structure in the western desert of Egypt were examined by many authors (El Gezeery et al. 1972; Moussa 1986a,b; RRI 1986; Keeley 1989; Shalaby et al. 2000; Dolson et al. 2001; Moustafa et al. 2003; Younes and Bek 2003; Metwalli and Bakr 2007; Moustafa 2008; Afify 2012; Nassar 2013; Shalaby et al. 2013; Boukhary, 2014; EL Bastawesy 2016; EL Bastawesy et al. 2020). The sedimentary cover of the northwestern desert was discovered to be from Cambrian to recent age (Fig. 3). Overlying the Alam El Buieb is the Alamein Formation, which represents a good marker for geologists and geophysicists (Ghanem et al. 1997). It is comprised mainly of shale and dolomite due to the Aptain transgression, and it is only present in the Nader-1 well in the study area. Kharita Formation is consisted of sandstone with thin shale intercalations and rare carbonate interbeds. It overlays the Alamein Formation. The Bahariya Formation is deposited on top of the Albian Kharita Formation in conformably set. It is mostly sandstone intercalated with shale, siltstone, and some limestone. The primary reservoir unit in the Khalda concession is the Lower Bahariya, while the Upper Bahariya is the secondary producer (Wehr et al. 2002). The Khoman is the youngest Upper Cretaceous Formation, consisting primarily of limestone and representing Maastrichtian/Campanian deposits (Schlumberger 1984).
Seismic and well log data were included in the dataset for this investigation. The seismic data comprises twenty 2D post-stack seismic sections and check shot data. The well logs are in the form of composite logs for four wells Nader-1, Nader-2, Nader-4, and Nader-8. The composite logs are neutron, gamma-ray, density, caliper, resistivity, and sonic logs. In addition to the averaged reservoir parameters for Nader-3 and Nader-6 wells from Khalda internal reports (Khalda 1997). Schlumberger's Petrel Software was utilized to evaluate the digital seismic data, while Interactive Petrophysics software was used to analyze the available well logs. The flowchart used to guide this study is shown in Fig. 4. Structure contour maps of the Upper and Lower Bahariya formations are used to determine the subsurface geologic setting. These maps were constructed by interpreting the seismic reflections of these formations. The petrophysical evaluation was performed by identifying the reservoir lithology using charts. The type of hydrocarbon in this reservoir is determined using pressure data. Then calculated petrophysical parameters (net-pay thickness, PHIE, Vsh, Sw, and Sh) of the reservoirs were mapped to illustrate the distribution of the petrophysical parameters laterally in reservoirs.
Subsurface geological interpretation transports the geologic meaning by extracting subsurface information from the seismic data (Chen and Sidney 1997). Seismic attributes are the parameters extracted from seismic data, such as frequency, seismic wave time, attenuation, and amplitude (Sheriff 1994; Brown 1996; Chopra and Marfurt 2005). This study used instantaneous phase as a type of physical post-stack seismic attribute and dip variance as a type of geometric attribute. A synthetic seismogram for the Nader-1well was created using the available check-shot to tie seismic data to well log data. The interpreted horizons in the seismic data were chosen based on the seismic well ties. It's common to interpret a set of marker horizons above and below the target to determine how structures were generated. Consequently, the top Khoman, top Kharita, and top Alamein formations have been chosen to determine the detailed structures affecting the Bahariya reservoir in the Nader field. Figure 5 (a) depicts the seismic section (arbitrary line-16). This line trends NE-SW and passes near the Nader-8 well. Figure 5(b) shows the results of applying instantaneous phase seismic attributes. As noticed, the faults and reflector terminations are better interpreted. Figure 5(c) shows that the five interpreted horizons (Khoman, Upper Bahariya, Lower Bahariya, Kharita, and Alamein formations) are divided by two normal faults (F3 and F6). These Faults formed the horst block in the central part of the research area. The Upper Bahariya, Lower Bahariya, Kharita, and Alamein formations are all affected by F3, which has a downthrown side towards the southwest. F6 has a downthrown side towards the northeastern direction, affecting all the picked horizons. The seismic section (Arbitrary line-17) that passes near the Nader-2 well and has a NE-SW trend is depicted in Fig. 6(a). Figure 6 (b) shows the results of applying the variance attribute to this arbitrary line. As noticed, faults are better interpreted. Figure 6(c) shows the interpretation of the five chosen horizons in this section. It is characterized by the existence of four normal faults (F1, F3, F6, and F7). Faults F1, F7, and F6 have the downthrown sides towards the northeastern direction, while fault F3 has the downthrown side towards the southwestern direction. The small rollover anticline is found on the downthrown side of F6, F1, and F3, which form the graben structure, while F3 and F7 form the horst structure.
Lithology Identification
There are many different types of log charts that are utilized to assess lithology, and many different combinations are addressed in this article (Schlumberger 1974; Dresser 1979). The density-neutron charts and the M-N charts are used in this study. On the density neutron cross plot, natural gas's influence appears as the plotted points drift in the northwest direction from the sandstone line. The M-N cross plot is based on fluid and log parameters, which are effectively combined in the Sonic, Density, and Neutron logs (Bruke et al. 1969). From the values of these logs, two functions M and N are computed and a cross-plot of these two quantities reveals lithology characteristics (Pirson 1977).
Reservoir Pressure Measurement
The fluid type in the formation (gas, oil, or water) and the depths of gas-oil contact and oil-water contact (OWC) can be shown by plotting formation pressure vs depth (Stewart and Wittmann 1979).
Petrophysical analysis of the Bahariya reservoir
The petrophysical analysis of the given data was performed using the following workflow:
1-Reservoir zonation
The depths of the reservoir zones are measured in feet.
2-Formation Temperature calculation
The geothermal gradient (G) is used to calculate the formation temperature (TFM) by the following equation (Knut 2010)
GG = \(\frac{100 \times (BHT - ST)}{TD}\) (1)
Where; the geothermal gradient (°F/100 ft.) is denoted by GG, the surface temperature (°F) is denoted by ST, the total depth (ft.) is denoted by TD, and the bottom hole temperature (°F) is denoted by BHT.
3-Clay volume analysis
The Gamma-Ray is utilized here to calculate the clay volume by the following equation (Bassiouni 1994)
IGR = \(\frac{(GRlog – GRmin) }{(GRmax – GRmin)}\) (2)
Where; GRmin is the minimum gamma-ray, IGR is the gamma-ray index, GRmax is the maximum gamma ray, and GR log is the gamma-ray reading from the log. A clay volume cutoff of 0.33 and 0.50 was used here for the Upper and Lower reservoirs, respectively.
4-Formation water resistivity (Rw): The Rw of logs can be determined using a variety of methods (Schlumberger 1987). The Rw value from core analysis = 0.035 ohm.m at 185°F (Khalda 1997).
5-Porosity determination: The total porosity is calculated as: ØT= (ØD+ ØN)/ 2 (Rider 2002). Where; ØD is porosity obtained from density and ØN is porosity obtained from neutron. After removing the shale effect, the effective porosity is calculated as follows: ØE= ØT - (ØCLAY * VCLAY). The porosity cutoff = 12%.
6-Water saturation determination
The water saturation is calculated in the shaly formation by the Indonesian equation (Poupon and Leveaux 1971).
where; Sw is the water saturation of formation, Rt is the true resistivity (log reading), Rw is the resistivity of formation water, Rsh is the resistivity of shale, Vsh is the volume of shale, Øe is the effective porosity, m is the cementation factor, a is the Archie constant, and n is the saturation exponent. This equation was applied to calculate the Sw in Upper Bahariya, while the Sw in Lower Bahariya was calculated using Archie's equation (Archie 1941).
(SW)n = \(\frac{\left(\text{a} \text{*} \text{R}\text{w}\right) }{\left(\text{m} \text{*} \text{R}\text{t}\right)}\) (4)
Where; Sw is the water saturation, n is the saturation exponent, Rw is the formation water resistivity, a is the tortuosity factor, Rt is the uninvaded zone resistivity, m is the cementation exponent, and Ø is the porosity. In this investigation, the water saturation cutoff was 70% and 60% for the Upper and Lower Bahariya Formations, respectively.
7-Bad-hole correction
Because all the wells in the study area were drilled with an 8.5-inch bit, any borehole diameter larger than 9.5 inches is considered a bad hole.
1-Seismic interpretation
Time structure contour maps show the subsurface geologic structural features of the horizons as a function of two-way reflection times. Fig. 7 (a-b) illustrates the two-way time (TWT) structural contour maps on the tops of Upper Bahariya and Lower Bahariya, respectively. The time decreases in the central part of the research area and towards the southeastern direction until reaching a minimum of -1075 milliseconds (Fig. 7a). This figure also shows that the maximum value of time is -1190 milliseconds in the southwestern direction. The two-way time has a maximum value of -1210 milliseconds in the southwestern direction and a minimum value of -1110 milliseconds southeastern direction (Fig. 7b). These low and high time anomalies correspond to the locations of structural highs and lows for the up-thrown and down-thrown blocks were separated by normal faults with NW-SE trends. These fault trends are consistent with Cretaceous tectonic movement, which lends credence to the fault interpretation trends. These maps show two sets of normal faults. The first set of faults (F1, F2, F4, F6, F7, F8, F10, F12, and F13) has downthrown sides towards the northeastern direction. The second one has downthrown sides towards the southwestern direction, such as faults (F3, F5, F9, F11, F14, and F15). Some faults formed the graben structure, such as (F1 & F14), (F1 & F3), (F2 & F3), (F6 & F9), and (F8 & F9). The other faults such as (F3 & F4), (F3 & F6), (F5 & F7), and (F3 & F7) formed the horst structure. Fig. 8 (a-b) illustrates the Upper and Lower Bahariya depth structure contour maps, respectively. The highest depth of the Upper Bahariya is in the northeastern part of the map, which reaches -5375 feet, and the shallowest reaches -4875 feet in the southeastern direction (Fig. 8a). The value of -5,500 feet represents the deepest part and lies on the southwest portion of the map, while the value of -5000 feet indicates the shallowest part and is found in the southeastern direction (Fig. 8b).
2- Petrophysical Evaluation
Determination of Lithology
Figure (9, a&b) illustrates the Neutron-Density cross plot for the Upper Bahariya Formation in the Nader-4 and Nader-8 wells, respectively. Fig. 9(c-d) illustrates the Neutron-Density cross plot for the Lower Bahariya Formation in the Nader-4 and Nader-8 wells, respectively. Most of the plotted points are clustered between the limestone and dolomite lines. The shale effect led to the shifting of the points to the dolomite line. The range of porosity is from 15 to 30% (Fig. 9a&b). The Lower Bahariya Formation has a varied lithology of sandstone and limestone (Fig. 9c-d). Porosity values range from 10 to 25%, and some points are shifted towards the dolomite line. Figure (10, a&b) illustrates the M-N charts for the Upper Bahariya Formation in Nader-1 and Nader-2, respectively. Figure (10, c&d) illustrates the M-N charts for the Lower Bahariya Formation in Nader-1 and Nader-2, respectively. Figure (10, a&b) depicts the mineralogical composition of the Upper Bahariya reservoir. Many of the plotted points tend to be in the calcite and dolomite parts, in addition to some points shifted downward because of the shale effect. The plotted points of the Lower Bahariya fall on the quartz sandstone, dolomite, and calcite parts, but some points shifted in the lower right direction due to the presence of shale (Fig. 10 c&d).
Pressure data analysis
Table (1) represents the repeat formation tester (RFT) results for the Lower Bahariya reservoir in the Nader-8 well. The analysis of these pressure data indicates that the oil gradient is 0.35 psi/feet, the water gradient is 0.5 psi/feet, and the true vertical depth of OWC in the Lower Bahariya reservoir is 5724 feet (Fig. 11). By knowing that the Kelly bushing is 594 feet in the Nader-8 well, the value of the sub-sea true vertical depth can be calculated by the following equation (Wohlmutter 2015) to equal -5130 feet.
TVD- TVDss =KB (5)
Where, TVD is the true vertical depth, TVDss is the sub-sea true vertical depth, and KB is the Kelly bushing. By knowing that the value of the TVDss of OWC is constant for the same reservoir in the field and by using the value of KB for each well in the previous equation, the TVD of the original OWC can be calculated as shown in Table (2).
Petrophysical analysis
Figure (12, a&b) shows the CPI plots for the Upper Bahariya in the Nader-1 and Nader-2 wells, respectively. In these plots, the neutron-density logs show that the Upper Bahariya reservoir mostly consists of mixed lithology of sandstone, siltstone, shale, and limestone. Because of the high volume of shale and the existence of radioactive minerals in the Upper Bahariya, the gamma-ray readings became high against the sand. The petrophysical analysis of the Nader-1 well showed a net pay of 2 feet with Sh of 37%, PHIE of 20%, Sw of 63%, and Vsh of 16% (Fig. 12a). The Nader-2 well has the thickest net pay of 11 feet with Sh of 46.3%, PHIE of 24%, Sw of 53.7%, and Vsh of 12.5 (Fig. 12b). The petrophysical analysis shows the highest value of Sw at 92% and the lowest value of Sh at 8%, so there is no pay zone in the Nader-4 well. The thickness of the net-pay is 5 feet in Nader-8, with Sh of 41%, PHIE equals 20.6%, Vsh of 15%, and Sw of 59%. The Upper Bahariya petrophysical parameters using the CPI plot are summarized in Table (3). Fig. 13 shows the CPI plots for the Lower Bahariya, with the original OWC in the Nader-1well. The petrophysical analysis of the Nader-1well showed a net-pay of 13.5 feet, PHIE of 18.1%, Vsh of 13.8%, Sh of 61%, and Sw of 39%. The petrophysical analysis of the Nader-2 well showed a net pay of 1feet with Sh of 44%, PHIE of 15%, Sw of 56%, and Vsh of 16%. As there are multiple oil zones in the Lower Bahariya, there are multiple oil contacts. Fig. 14 illustrates the CPI plot for Lower Bahariya in Nader-8 with the original OWC and with the ODT (Oil Down to) at depths of 5724 ft. and 5868 feet, respectively. This well has the highest thickness of net-pay about 33 feet, with Sh of 65%, PHIE of 23%, Sw of 35%, and Vsh of 12.1%. The petrophysical parameters of the Lower Bahariya using the CPI plot are illustrated in Table (4). The average reservoir parameters in the four wells and those in the Nader-3 and Nader-6 that were taken from Khalda's internal report (Khalda 1997) were mapped to reflect their distribution laterally. Figure (15) shows the Upper Bahariya reservoir's net-pay thickness distribution map. This figure shows an increase in the net-pay thickness in the central part of the research area until reaching a maximum of 11 feet in the Nader-2 well and an increase in the northeastern direction. It also shows decreases in the southeastern and western directions, with a minimum value of zero in Nader-4. Figure (16, a&b) shows the PHIE and Vsh distribution maps of the Upper Bahariya reservoir, respectively. The central and northeastern parts of the mapped area have higher PHIE, while the rest of the area has lower PHIE (Fig. 16a). It also illustrates that PHIE values range from 13% at Nader-4 to 24% at Nader-2. The increasing and decreasing directions of the effective porosity map changed to the opposite direction for the Vsh distribution map (Fig. 16b). At the Nader-2 well, the Vsh is at its lowest point of 12.5%, while at the Nader-4 well; it reaches its greatest point of 23% (Fig. 16b). Figure (17, a&b) shows the Upper Bahariya reservoir's water and hydrocarbon saturation distribution maps, respectively. The Sw increases towards the western direction and decreases in the central part and in the eastern direction (Fig. 17a). The Nader-2 well has the lowest Sw value of 53.7%, while the Nader-4 well has the highest Sw value of 92% (Fig. 17a). The increasing and decreasing directions for the Sw distribution map changed to the opposite direction for the Sh distribution map (Fig. 17b). The Sh value for the Nader-4 well is 8%, while the Sh values for the Nader-2 and Nader-3 wells are 46.3 percent and 45.7 percent, respectively (Fig. 17b). Figure (18) shows the Lower Bahariya reservoir's net-pay thickness distribution map. Its thickness increases in the northeastern direction and decreases in the other directions of the research area. The Nader-6 well has a minimum value net-pay thickness of 0 feet, while the Nader-8 well has a maximum net-pay thickness of 33 feet (Fig. 18). The PHIE increases towards the northeastern direction while it decreases towards the northwest and reaches its least value towards the southern direction of the research area. The PHIE values range between 14% at Nader-6 well and 23% at Nader-8 well (Fig. 19a). The increasing and decreasing directions for the Vsh distribution map (Fig. 19b) changed to the opposite direction for the PHIE map. The Vsh attains its lowest value of 12.1% at the Nader-8 well and its highest value of 18% at the Nader-6 well (Fig. 19b). Figure (20, a&b) shows the water and hydrocarbon saturation distribution maps of the Lower Bahariya reservoir, respectively. Sw increases towards the northwestern direction and reaches its maximum value towards the southern direction and decreases towards the northeastern direction of the Lower Bahariya reservoir area (Fig. 20a). The Sw attains the lowest value of 35% at the Nader-8 well and a high value of 89% at the Nader-6 well (Fig. 20a). Figure (20) shows the increasing and decreasing directions of Sh map as it becomes in opposite direction for Sw map. The Nader-8 well has the highest hydrocarbon saturation of 65%, while the Nader-6 well has the lowest at 11% (Fig. 20b). When compared to the petrophysical parameters and hydrocarbon potential of the Bahariya reservoir in other Khalda ridge wells such as the Kenz, Yasser, and Salam wells, these results are considered satisfactory for hydrocarbon production (Shady et al. 2010). The estimated porosities of the investigated intervals are good. In Salam-5 well, the porosity of the upper Bahariya reservoir was 26%, and in Salam-17 well, the lower Bahariya reservoir's porosity was 23%. The formation is saturated with hydrocarbons according to the fluid analysis, which reaches 62.6 % in the Kenz well (Upper Bahariya) and 68.6 % in the Salam-5 well (Lower Bahariya), respectively (Shady et al. 2010).
Proposed evaluation
Because of the integration of subsurface and petrophysical evaluations in this study, three new locations are proposed. Figure (21, a&b) shows these three locations on the upper and lower Bahariya depth maps, respectively. Proposed locations 1 and 2 are positioned as being in the structurally high areas and on the 3-way dip closures that would be suitable for oil and gas accumulations. Proposed location-3 is located in a structurally high area that might be a 3-way dip closure or a 4-way dip closure. There is insufficient data to validate this point, since this area is at the end of the utilized seismic data. Therefore, it could be a possible area for drilling exploratory wells. Figure (22, a-c) depicts the seismic lines (x-line-15, x-line-10, and arbitrary line-17) that pass through proposed locations 1, 2, and 3, respectively. These figures confirm our structure and demonstrate the up dip for these locations. Moreover, if the petrophysical parameter maps are extrapolated, the expected value for these prospects will be calculated. The expected value of net-pay thickness will be 33 feet, 6.5 feet, and 24 feet for the proposed locations 1, 2, and 3, respectively (Fig. 23). The expected values of PHIE will be 22.2%, 17.4%, and 21.4% for the proposed locations 1, 2, and 3, respectively (Fig. 24). For proposed locations 1, 2, and 3, hydrocarbon saturation is projected to be 45%, 53.5%, and 67%, respectively (Fig. 25). The values of 55%, 46.5%, and 33% are the expected values of the water saturation for proposed Locations 1, 2, and 3, respectively (Fig. 26). For proposed locations 1, 2, and 3, shale volume is projected to be 13.5%, 13.55%, and 12.55% (Fig. 27). According to the petrophysical properties of the Upper Bahariya Formation, these locations have a range of 1 to 6 feet of net-pay thickness. They also have a range of 14.8 to 20.7 for effective porosity and a range of 11.4% to 21.8% for shale volume. The range of water saturation is 45.5% to 86% and the range of hydrocarbon saturation is 14% to 54.5%.
The integration of 2D seismic interpretations and well log data was utilized to estimate hydrocarbon potential at the Bahariya Formation, Nader Field, Shushan Basin, northwestern desert. Twenty seismic lines covering the research region were interpreted to identify the seismic reflectors. The remarkable tops of Upper and Lower Bahariya have been chosen to highlight the evolution of structural elements influencing the Bahariya reservoir. The two-way time of the Upper Bahariya formation ranges from − 1075 to -1190 milliseconds. The lower Bahariya formation has a two-way time range from − 1110 to-1210 milliseconds. The depth values range from − 4875 to-5375 feet and from − 5000 to-5500 feet for the Upper and Lower Bahariya formations, respectively. The structural analysis is found to be linked to the recognized regional tectonic movements of the northwest desert. The locations of structural highs and lows for the upthrown and downthrown fault blocks separate normal faults with a NW-SE trend. These fault trends match the Cretaceous tectonic movement, which in turn supports the fault interpretation trends. This dominant trend created a series of fault patterns that were present in the graben and horst structures. This study also shows valuable and commercial petrophysical analysis in the Nader field. The neutron-density charts of the Upper and Lower Bahariya indicate a lithology that is a variety of sandstones and limestone, and because of the shale effect, some points drifted toward the dolomite line. The M-N charts have been performed to confirm this lithology distribution. According to the pressure analysis for the Nader-8 well, the gradient is 0.305 psi/feet, which indicates that the hydrocarbon type is oil. It also reflects a water gradient of 0.5 psi/feet, and the OWC depth of -5130 TVDss. The CPI demonstrated that the Upper Bahariya Formation has oil potential in three wells, Nader-1, Nader-2, and Nader-8, while the Lower Bahariya Formation has oil potential in all the studied wells. The maps of the Upper and Lower Bahariya reservoirs' petrophysical parameters, which include net-pay, PHIE, and Sh maps, reflect an increase in the opposite direction of the Vsh and Sw maps. As a result, three new locations are proposed to be prospective wells in the Nader field. In these three locations, net pay and PHIE increase, whereas Vsh and Sw decrease.
Acknowledgement
The authors are grateful for the permission to publish this data from the Egyptian General Petroleum Corporation (EGPC) and Khalda Petroleum Company.
- Abdelmaksoud A., Amin A.T., El-Habaak G.H., Ewida H. F. (2019). Facies and petrophysical modeling of the Upper Bahariya Member in Abu Gharadig oil and gas field, north Western Desert, Egypt. Journal of African Earth Sciences, 149, 503-516.
- Aboelhassan, N., Tarabees, E., & Alaa, M. (2017). Reservoir evaluation of Bahariya Formation in tut oil field, north Western Desert, Egypt. GEOMATE Journal, 12(29), 195-203.
- Afify, W. (2012). Reservoir characterization of Alam El Bueib pay zones in Tut oil field, Western Desert, Egypt. [Ph.D. Thesis]. Zagazig Univ., Egypt. p 317.
- Alsharhan A. S., Abd El‐Gawad E. A. (2008). Geochemical characterization of potential Jurassic/Cretaceous source rocks in the Shushan Basin, northern Western Desert, Egypt. Journal of Petroleum Geology, 31(2), 191-212.
- Archie, G. E. (1941). The Electrical Resistivity Log as an Aid in Determining Some Reservoir Characteristics, (Dallas Meeting, October 1941).
- Bassiouni, Z. (1994). Theory, measurement and interpretation of well logs. SPE textbook series, vol. 4, 372 p.
- Boukhary, M., El Nahas, S., Abd El Naby, A., Abdel Aal, M. H., Mahsoub, M., & Faris, M. (2014). Seismic and sequence stratigraphy of Upper Cretaceous–Tertiary succession, eastern Abu-Gharadig Basin, Western Desert, Egypt. Stratigraphy, 11(2), 109-141.
- Brown, A. R. (1996). Seismic attributes and their classification. The leading edge, 15(10), 1090-1090.
- Bruke, J. A., Campbell, R. L., Schmidt, A. W. (1969). The litho-porosity crossplot. The log analyst (SPWLA), 10 (6).
- Chen, Q., Sidney, S. (1997). Seismic attribute technology for reservoir forecasting and monitoring. The Leading Edge, 16(5), 445-448.
- Chopra, S., Marfurt, K. J. (2005). Seismic attributes—A historical perspective. Geophysics, 70(5), 3SO-28SO.
- Dolson, J. C., Shann, M. V., Matbouly, S., Harwood, C., Rashed, R., Hammouda, H. (2001). The petroleum potential of Egypt. In: in Petroleum Provinces of the 21st Century v. Memoir 74, W. A. Morgan Ed. American Association of Petroleum Geologists, Tulsa, pp 453–482
- Dresser, A. (1979). Log interpretation charts. Dresser industries Inc., Houston, Texas, 107 p.
- EGPC (Egyptian General Petroleum Corporation) (1992). "Western Desert, oil and gas fields, A comprehensive overview", 431p.
- EL Bastawesy, M., Afify, W., Barakat, M., EL Gendy, N. (2020). Petroleum System analyses of middle jurassic and early cretaceous rocks, Matruh Basin, North Western Desert, Egypt. European Association of Geoscientists & Engineers, Conference Proceedings, 82nd EAGE Annual Conference & Exhibition, vol 2020. pp 1–5.
- EL Bastawesy, M. A. (2016). Hydrocarbon Potentialities of the lower Cretaceous rocks in jade field, Western Desert, Egypt. PhD. Thesis. Tanta Univ., Egypt, p 287.
- El Gezeery, N. H., Mohsen, S. M., Farid, M. I. (1972). Sedimentary basins of Egypt and their petroleum prospects. 8th Arab Petrol. Conf., Paper No. 83 (B-3). Algiers, p 13.
- Fagelnour M. S. , Metwalli F. I., Shendi E. H. (2018). Structural and facies modeling of the Lower Cretaceous Alam El Bueib reservoirs in the Shushan Basin, Western Desert, Egypt. Arab. J.Geosci. (2018) Vol. 11 (9), pp. 1-24.
- Farrag, G. H., Baghdady, A., Elnaggar, O. M. (2021). Petrophysical attributes of the middle zone of the Bahariya Formation as a producing reservoir using core analysis correlations and log evaluation, Abu Sennan area, Egypt. Journal of African Earth Sciences, 180, 104225.
- Ghanem, M. F., Hammad, M. M., Maky, A. F. (1997). Organogeo chemical evaluation of the subsurface Lower Cretaceous rocks of Matruh Basin, North Western Desert, Egypt. El Mini Science Bulletin 10 (2):81–107.
- Keeley, M. L. (1989). The Paleozoic history of the Western Desert of Egypt. Basin Res. 2:35–48.
- Khalda Petroleum Company, (1997). Nader-2 well prognosis, internal report, 3p.
- Knut, P. (2010). Petroleum Geoscience: From Sedimentary Environments to Rock Physics, second edition, Springer publisher. University of Oslo, Norway.
- Meshref, W. (1982). Tectonic framework. In: Said R (ed) The Geology of Egypt. Balkema Publishers, Rotterdam, Netherlands, pp 113–156.
- Metwalli F. I., Shendi E. H. Fagelnour M. S. (2021). Core and well logs interpretation for better reservoir characterization in Shushan Basin, Egypt. Arab. J.Geosci. (2021) Vol. 14, pp. 1-14. https://doi.org/10.1007/s12517-021-08819-0
- Metwalli, F., Shendi, H., Hart, B., Osman, W. (2018). 3D Seismic structural analysis and basin modeling of the Matruh Basin, Western Desert, Egypt. Int J Geophys 2018:4931307. https://doi.org/10.1155/2018/4931307
- Metwalli, F. I., Bakr, A. M. (2007). Seismostratigraphic Analysis of the Alam El Bueib Reservoir Sand, South Umbarka Area, Western Desert, Egypt”, ISESCO, vol. 3, pp. 64-87.
- Metwalli, F. I., Pigott, J. D. (2005). Analysis of petroleum system criticals of the Matruh–Shushan Basin, Western Desert, Egypt. Petroleum Geoscience, 11(2), 157-178.
- Moussa, S. (1986a). Evolution of the sedimentary basins of the North Western Desert, Egypt. In: Proceedings of the EGPC 8th Exploration and Production Conference, vol 1. Egyptian General Petroleum Corporation Bulletin, Cairo, pp 66–84.
- Moussa, S. (1986b). Evolution of the sedimentary basins of the North Western Desert, Egypt. EGPC. In: 8th Petrol. Expl. Prod. Conf., Cairo, pp 1–22.
- Moustafa, A. R. (2008). Mesozoice Cenozoic basin evolution in the Western Desert of Egypt. In: Salem M, El-Arnauti A, Saleh A (eds) 3rd Symposium Sedimentary Basins of Libya, vol 3. The Geology of East Libya, pp 29–46.
- Moustafa, A. R., Saoudi, A., Moubasher, A., Ibrahim, I. B., Molokhia, H., Schwartz, B. (2003). Structural setting and tectonic evolution of the Bahariya Depression. Western Desert, Egypt, GeoArabia 8(1):91–119.
- Nassar, M. A. (2013). Sedimentological studies and hydrocarbon potentialities of the lower cretaceous Alam El-Buieb formation, North Western Desert, Egypt. [M.Sc. Thesis]. Tanta University, PP206.
- Pirson, J. S. (1977). "Geologic Well Log Analysis", Gulf Publishing Company. Huston,London, Paris. Taka pp.165- 169.
- Poupon, A., Leveaux, J. (1971). Evaluation of Water Saturations in Shaly Formations, SPWLA 12th Annual Logging Symposium, paper O.
- Rebortson Research International Limited (RRI), (1986). Palynological analysis of designated lower Cretaceous and Jurassic intervals in Khalda concession, Western Desert, Egypt. Unpublished report prepared for EGPC.
- Rider, M. H. (2002). The geological interpretaion of well logs 2nd edittion. 291p. Sutherland, Rider-French Consulting.
- Said, R. (1962). The geology of Egypt. Elsevier Publ. Co., Amsterdam, Oxford and New York, p 277.
- Sarhan, M. A. (2021). Geophysical assessment and hydrocarbon potential of the Cenomanian Bahariya reservoir in the Abu Gharadig Field, Western Desert, Egypt. Journal of Petroleum Exploration and Production Technology, 11(11), 3963-3993.
- Schlumberger (1974). Log interpretation manual/application, Houston, Schlumberger well services, Inc., Vol. 2.
- Schlumberger (1984). Well evaluation conference, Egypt 1984. 243 p.
- Schlumberger (1987). Log interpretation principles/applications, 198 p.
- Schlumberger (1995). Well evaluation conference, Egypt 1995. 87 p.
- Shady, A. A., El-Shishtawy, A. M., Hameed, A. A., AbdelKader, T. (2010). RESERVOIR CHARACTERIZATION OF THE UPPER CRETACEOUS BAHARIYA FORMATION, KHALDA RIDGE, NORTH WESTERN DESERT, EGYPT. In Proceedings of the 6th International Symposium on Geophysics, Tanta, Egypt (pp. 34-46).
- Shalaby, M. R., Abdel Hamid, A. T., Abu, A. S. (2000). Structural setting and sedimentary environments using dipmeter analysis of some Jurassic reservoirs, North Western Desert, Egypt. In: in: 5th International Conf., Geology of the Arab World. Cairo Univ., Egypt, pp 217–220.
- Shalaby, M. R., Hakimi, M. H., Abdullah, W. H. (2013). Modeling of gas generation from the Alam El-Bueib Formation in the Shoushan basin, northern Western Desert of Egypt. Int. J. Earth Sci. 102:319–332
- Sheriff, R. E. (1994). Encyclopedia dictionary of exploration geophysics Soc. Expl. Geophys.
- Stewart, G., Wittmann, M. (1979). Interpretation of the Pressure Response of the Repeat Formation Tester.Society of Petroleum Engineers, (January 1), Doi: 10.2118/8362-MS.
- Sultan, N., Halim, M. (1988). Tectonic framework of northern Western Desert, Egypt and its effect on hydrocarbon accumulations. In:EGPC 9th Petroleum Exploration and Production Conference,Cairo, Egypt, pp. 1–19.
- Wehr, F., Youle, J., Pemberton, G. (2002). Sequence stratigraphy and sedimentology of the Bahariya Formation, Khalda Concession, Western Desert, Egypt. American Association of Petroleum Geologists, International meeting, Cairo, Egypt, (Abstract Volume unpaginated).
- Younes, M. A. (2005). Petroleum Geochemistry and Potential Source Rock Correlation in the 869 Shushan Basin, North Western Desert, Egypt. Pet. Sci. Technol.; 23(5–6): 507–536.
- Younes, M. A., Bek, M. (2003). Alamein basin hydrocarbon potentials, northern Western Desert, Egypt. In: AAPG Annual Convention, Salt Lake City, 11–14 May 2003, vol 90013. Extended abstract, Tulsa.
Table 1
Pressure data results for Lower Bahariya in Nader-8.
|
Mobility (md) |
Pressure (psi) |
Measured depth (ft.) |
|
92 |
2135.70 |
5694.00 |
|
645 |
2138.00 |
5702.00 |
|
28 |
2139.20 |
5706.00 |
|
68 |
2140.70 |
5710.00 |
|
40 |
2141.80 |
5713.00 |
|
401 |
2142.70 |
5717.10 |
|
35 |
2145.40 |
5725.00 |
|
101 |
2146.30 |
5727.10 |
Table 2
Measured depth of the original OWC.
|
TVD OR MD (ft.) |
KB (ft.) |
Wells |
|
5738 |
608 |
Nader-1 |
|
5714 |
584 |
Nader-2 |
|
5738 |
608 |
Nader-4 |
Table 3
Petrophysical parameters of the Upper Bahariya in Nader Field.
|
Hydrocarbon Saturation (%) |
Water saturation (%) |
Volume of shale (%) |
Effective porosity (%) |
Net reservoir (ft.) |
Net pay (ft.) |
Well |
|
37 |
63 |
16 |
20 |
7 |
2 |
Nader-1 |
|
46.3 |
53.7 |
12.5 |
24 |
16 |
11 |
Nader-2 |
|
8 |
92 |
23 |
13 |
20 |
0 |
Nader-4 |
|
41 |
59 |
15 |
20.6 |
23.5 |
5 |
Nader-8 |
Table 4
Petrophysical parameters of the Lower Bahariya in Nader field.
|
Hydrocarbon saturation (%) |
Water saturation (%) |
Volume of shale (%) |
Effective porosity (%) |
Net reservoir (ft.) |
Net pay (ft.) |
Well |
|
61 |
39 |
13.8 |
18.1 |
281.5 |
13.5 |
Nader-1 |
|
44 |
56 |
16 |
15 |
77.5 |
1 |
Nader-2 |
|
45 |
55 |
14.5 |
16 |
80.5 |
2 |
Nader-4 |
|
65 |
35 |
12.1 |
23 |
351.5 |
33 |
Nader-8 |
No competing interests reported.