Mohamed Ragab Shalaby

Organic geochemical characteristics and interpreted depositional environment of the Khatatba Formation, northern Western Desert, Egypt

The Middle Jurassic Khatatba Formation in the northern Western Desert of Egypt was evaluated in terms of organic matter abundance, type and thermal maturity, as well as for some organic petrographic characteristics. Depositional environments were interpreted based on organic geochemical (Rock-Eval pyrolysis, extract analysis, and biomarker distributions) and organic petrological methods. Organic carbon contents range between 1.0 and 32.5 wt. %. The Khatatba shale and coaly shale samples have hydrogen index values in the range of 63 to 261 mg hydrocarbon (HC)/g total organic carbon, with mixed types 2–3 and 3 kerogens. Mean vitrinite reflectance (Ro) between 0.77 and 1.07% is in reasonably good agreement with pyrolysis Tmax (temperature at maximum of S2 peak) data (438–459C). Organic-rich sediments of the Middle Jurassic Khatatba Formation have very good source rock generative potential and have obtained thermal maturity levels equivalent to the oil window. The main generation products are gas with very limited liquid HCs (oil or condensate). Seven shale and coaly shale samples from Khatatba Formation were characterized using gas chromatography (GC) and GC–mass spectrometry techniques. The Khatatba samples are characterized by the predominance of C14-C24 alkanes, a pristane/phytane ratio of less than 2, abundant C27 regular steranes, and the presence of tricyclic terpanes. These are consistent with the suboxic marine-environment conditions for the Khatatba source rock. Biomarker parameters for these samples generally indicate a mixture of land- as well as marine-derived organic-matter input. The maturity indicators based on C32 22S/(22S + 22R) homohopane and C29 20S/(20S + 20R) and /( + ) sterane ratios reveal that the Khatatba samples are thermally mature and have reached the peak oil-window maturity supporting the Ro data.

Integrated reservoir characterization of the Paleocene Farewell Formation, Taranaki Basin, New Zealand, using petrophysical and petrographical analyses

A reservoir characterization study, using petrophysical and petrographic analyses, has been made on the Paleocene Farewell Formation in the Taranaki Basin, New Zealand, based on five selected wells. Farewell Formation is largely a sandstone formation belonging to the Kapuni Group. The integrated study has shown that Farewell Formation is a good promising reservoir with average effective porosity of 17.7% and permeability of 415 mD. The petrographic study indicates the occurrence of abundant intergranular and secondary pores. It also proved that the Farewell Formation has been affected by several diagenetic features. Compaction, cementation and clay mineral authigenesis are the most common. Quartz and feldspar overgrowths have been recorded in many samples, and secondary porosity due to dissolution is also observed. In general, good reservoir quality features are dominant in the Farewell Formation and diagenesis has little effect on the reservoir quality. These findings are supported by well log interpretation results, which confirm good sand and net pay zones are available with very low average water saturation (24.9%).

Fracture detection using conventional well logging in carbonate Matulla Formation, Geisum oil field, southern Gulf of Suez, Egypt

The non-availability of the advanced tools such as FMI and Borehole Televiewer has led to the use of conventional well logging methods in the examination of potential fractures and ultimately help in reservoir characterization and development. This study uses the said conventional well log data for fracture detection in the Upper Cretaceous Matulla Limestone Formation in the Geisum oil field, southern Gulf of Suez province, Egypt. Different applications have therefore been integrated together, which include the Secondary Porosity Index (SPI) with tri-porosity crossplot (M–N), the natural gamma ray spectroscopy (NGS), the Dual Laterolog–MSFL logs separation, the litho-density and compensated neutron logs and the Variable Density log (VDL), which is based on the responses of the compressional and shear waves in front of fractured zones. Good secondary porosity is prevalent in the Matulla Formation with SPI values reaching maximum values of 21.5 and 15.1% in the studied wells. Three and six fractured zones have been recognized in Geisum A-2 and Tawila N-1 wells, respectively, based on SPI logs. Several of these proposed zones are supported by other tools such as NGS, photoelectric (Pe), and VDL and fracturability Index (FI). This integrated method using various conventional well log has produced results suggesting great probability in fracture identification in the carbonate Matulla Formation.

Structural Modeling of the Maui Gas Field, Taranaki Basin, New Zealand

Abstract 3D seismic and well log dataset were used jointly to build a structural model of the Late Cretaceous to Pliocene sedimentary sequence in the Maui Gas Field, to predict structural mechanics in the Taranaki Basin with geostatistics. Three phases of tectonic movements affected by faulting in this field were identified by this structural model: Late Cretaceous to Palaeocene rifting phase, Late Eocene to Miocene compressive faulting phase, and Plio-Pleistocene differential (compressive faulting in Maui South, normal fault activity in Maui North) faulting phase. Different phases of tectonic movements resulted in different structural patterns, Early Oligocene formations have abundant normal faults with slight slip and higher dip angles (40°-70°), and lower dip angle in the north (10°-15°) than in the south (15°-20°); Mid-Oligocene to Late Miocene formations contain low angle reverse faults (20°-40°), showing the structures in this period were affected by compressive stress on the whole; structural inversion occurred during mid-Oligocene to Pliocene, indicating the structural stress was contraction first and extension later in this period.

Characterizing site response in the Attock Basin, Pakistan, using microtremor measurement analysis

The Attock Basin is situated close to the northwest of Pakistan. Recent seismic event of October 2015 (7.5Mw) near the Pakistan Afghanistan border has proved that the area of interest is seismically active and triggered a series of aftershocks of magnitude even greater than 6.5Mw. This seismic activity has posed danger to the future of the people and infrastructure especially to the northwestern part of the country. Therefore, site response analysis is essential for estimating local site conditions in response to seismic events. Ambient noise recordings were made at 50 sites within urban and semi-urban settlements in the Attock Basin to analyze the site response of the small but densely populated basin. At each of these sites, the fundamental frequency of the soft sediments (f0), the amplitude (A0) of corresponding H/V spectral ratios, the thickness of soft sediment (H) lying over competent lithology, and the soil vulnerability index (Kg) were studied. Results were correlated with sparsely available borehole data to enhance the credibility of the study conducted for microzonation and predicting the site response to earthquake seismicity in the Attock Basin. The soil vulnerability index was found to range from moderate to high. Results clearly showed that the study area exhibits low to moderate fundamental frequency with greater soft sediment thicknesses distributed throughout the study area. Moreover, higher impedance contrasts were found at most of the sites within the central part of the Attock Basin, thus reflecting a moderate to high susceptibility of damage in those regions in response to seismic events.

Seismic interpretation and structural modelling of Kupe field, Taranaki Basin, New Zealand

Kupe field is a gas condensate field located in the southern Taranaki Basin. In the present study, 3D seismic and well log data sets were used to interpret and model Kupe structures. The primary objective of the study was to develop a structural model for the complete reservoir package in the Kupe field which composes of three horizons the North Cape, Farewell and Otaraoa formations. The three horizons were interpreted using time section and then converted into depth domain using the velocity model. The results demonstrate the successful establishment of the structural model to incorporate fault framework model, structural mechanics and geometric distributions of the structural features in the complex Southern Inversion Zone of Taranaki Basin. The reservoir package experienced extensional and contractional regimes during Late Cretaceous to Eocene and Eocene to Miocene epoch, respectively; as a consequence, both normal and reverse styles of faulting are observed. Normal faulting is more obvious in the sections taken from the northern part of the seismic cube while reverse faulting is more prominent in southern parts of the seismic cube. Reservoir package is compartmentalized by moderate- to high-angle (35°–87°) dip slip faults with NE–SW orientation. The proposed 3D structural model provides a unique combination of subseismic interpretations and a geostatistical modelling approach for understanding major fault mechanism, and it provides a significant platform for designing future drilling campaigns for Kupe field’s development.

Log-based petrophysical analysis of Khatatba Formation in Shoushan Basin, North Western Desert, Egypt

This paper aims to investigate the good reservoir quality and hydrocarbon potentiality of the Khatatba Formation, Qasr Field in the Shoushan Basin of the North Western Desert, Egypt by combining results from log-based petrophysical analysis, petrographic description and images from scanning electron microscope (SEM). Promising reservoir units are initially identified and evaluated through well log analysis of three wells in the field of study. Petrophysical results are then compared with petrographic and SEM images from rock samples to identify features that characterize the reservoir quality. Well log results show that Khatatba Formation in the study area has good sandstone reservoir intervals from depths ranging from 12848 ft to 13900 ft, with good effective porosity records of 13–15% and hydrocarbon saturations of greater than 83%. Petrographic analysis of these sandstone reservoir units indicate high concentrations of vacant pore spaces with good permeability that can be easily occupied by hydrocarbon. The availability of these pore spaces are attributed to pore-enhancing diagenetic features, mainly in the form of good primary porosity and dissolution. SEM images and EDX analysis confirmed the presence of hydrocarbon, therefore indicating a good hydrocarbon-storing potential for the Khatatba Formation sandstones.

Seismo-stratigraphic and structural interpretation of seismic data of Titas gas field, Bengal basin, Bangladesh

In the present study, seismic interpretation has been carried out over Titas structure of Bengal basin, Bangladesh to figure out its seismo-stratigraphic and structural behavior. Seven well marked reflecting horizons (R-01 to R-07) have been identified within the Neogene sedimentary sequences using 18 seismic sections and well log data. A new seismic stratigraphy of Neogene sequences has been proposed for the Titas structure ruling out the traditional lithostratigraphy. The studied structure has been divided into 3 megasequences (MS1, MS2 and MS3). Reflector R-01 and R-03 represent the tops of the megasequence 2 (MS2) and megasequence 1 (MS1) respectively. These well marked reflectors are correlated with the top of the traditional litho-groups called Tipam and Surma. Reflectors R-02 and R-04 represent acoustic impedance boundaries within MS2 and MS1 due to lithological gradation. However, R-02 and R-04 are not considered as sequence/ formation boundaries because geologically these are not well defined. Reflectors R-05, R-06 and R-07 represent top of the gasbearing zones A, B and C that belongs to MS1. All these interfaces or reflectors are anti-form with a central long crestal zone. It forms a north-south trending semi-domal sub-surface anticlinal structure having a semi-dome shaped closure. The structure is asymmetric with steeper eastern flank and gentler western flank. The crestal region is essentially plain with discontinuous reflection. The semidomal nature of the anticline is in contrast to the neighboring narrow anticlines. Structural pattern suggests its development in relation to the NE-SW trending stress field due to convergence of Indian plate with Burmese plate. Structures of the shallower and deeper reflectors are formed at different phases of structural development.