Figure 5- - uploaded by Khalid Shoaib
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Ratana structural framework, including the basement, top salt and top reservoir interval, and major faults. Note the progressive influence of back thrusting east-west.
Source publication
Exploration success in fold-and-thrust belts, like the Potwar petroleum province, is impacted by seismic imaging challenges and structural complexity. Success partly relies on the ability to validate subsurface models and model a range of properties, such as reservoir permeability. This is particularly important in the case of tight carbonate reser...
Contexts in source publication
Context 1
... the case of the Ratana model, the top Eocene, top Sakesar, top Salt and top Basement are the horizons constraining the architecture of the structural framework ( Figure 5). The structural framework maintains a constant stratigraphic thickness between the top Eocene and top Sakesar. ...
Context 2
... transition from thick to thin-skinned tectonics along the main thrust is reflected by a wider wavelength to the east and shorter wavelength to the west. This has a direct effect on fault fracture density on anticline crests (Figure 5), which is more prevalent in the western part of the structure, affected by thick-skinned tectonics. ...
Citations
... Seismic imaging constraints and structural complexity affect exploration success in the Upper Indus Basin (UIB) (fold-and-thrust belts) and other basins worldwide. Geological and geophysical modeling approaches would be used to overcome these problems, reduce uncertainty, and boost exploration success (Wrobel-Daveau et al., 2021). The Indus Basin is noteworthy because it includes around 90% of Pakistan's total hydrocarbon conventional drilled wells. ...
Geocellular modeling has become extremely important, linking all petroleum disciplines, and being widely used in simulation and production forecasting in complex basin studies. In this study, we focused on the Minwal–Joyamair Fields in the Upper Indus Basin (UIB), Pakistan, which contains Cambrian to Eocene reservoir formations. Changes in sedimentary environments and structural activities within the UIB have resulted in reservoir heterogeneity, which has adversely affected reservoir performance, and it is still not fully understood. Geocellular modeling was used in this study to better understand the structural framework of the Cambrian to Eocene formations in the UIB. The 2D seismic and well log data from the Minwal–Joyamair Fields are the primary data for building the geocellular model for the Eocene (Chorgali, Sakesar) and Paleocene (Lockhart) reservoirs. The developed structural model is then populated with petrophysical properties such as porosity. The upscaled porosity for the Eocene carbonate rock units ranges 1–3%. On the other hand, the Cambrian and Permian (Tobra & Khewra) clastic reservoirs bear porosity of 3–10%. The upscaled porosity can be utilized to predict the lateral and vertical distribution in these reservoirs. Furthermore, the evaluated upscaled correlation for Eocene reservoirs (80–90%), whereas for Permian (Tobra) and Cambrian (Khewra) reservoirs, it lies between 60 and 70 %. Apart from data availability, a complete geocellular model of the field was produced, encompassing the petrophysical and facies model. The geocellular models created a high-resolution 3D reservoir model of this complex geology that can be applied to similar geology worldwide to identify prospective zones.
... 40 Studies conducted elsewhere 4344 suggested that the distributions of porosity and permeability in Eocene carbonates are controlled by depositional, diagenetic, and deformational processes. According to Wrobel-Daveau and Barracloughy, 45 validation of reservoir properties in the Potwar Basin, particularly for the Eocene Sakesar Limestone, is key to success. Fahad and Khan 46 mentioned in their study that the reduction in rock volume caused by mechanical compaction potentially deteriorates the carbonate reservoir quality. ...
The carbonate reservoir quality is strongly reliant on the compaction process during sediment burial and other processes such as cementation and dissolution. Porosity and pore pressure are the two main factors directly affected by mechanical and chemical compactions. Porosity reduction in these carbonates is critically dependent on the overburden stress and subsidence rate. A variable sediment influx in younger basins may lead to changes in the reservoir quality in response to increasing lithostatic pressure. Deposition of molasse sediments as a result of the Himalayan orogeny caused variations in the sedimentation influx in the Potwar Basin of Pakistan throughout the Neogene times. The basic idea of this study is to analyze the carbonate reservoir quality variations induced by the compaction and variable sediment influx. The Sakesar Limestone of the Eocene age, one of the proven carbonate reservoirs in the Potwar Basin, shows significant changes in the reservoir quality, specifically in terms of porosity and pressure. A 3D seismic cube (10 km 2) and three wells of the Balkassar field are used for this analysis. To determine the vertical and lateral changes of porosity in the Balkassar area, porosity is computed from both the log and seismic data. The results of both the data sets indicate 2−4% porosities in the Sakesar Limestone. The porosity reduction rate with respect to the lithostatic pressure computed with the help of geohistory analysis represents a sharp decrease in porosity values during the Miocene times. Pore pressure predictions in the Balkassar OXY 01 well indicate underpressure conditions in the Sakesar Limestone. The Eocene limestones deposited before the collision of the Indian plate had enough time for fluid expulsion and show underpressure conditions with high porosities.
... The Potwar Basin is confined by the Indus River to the west and from east by the Jhelum River, Salt Range in south and Kalachitta-Margalla hill ranges in the north (Shah and Abdullah, 2017). The basin is more extensively deformed in the northern part and is characterized by east-west complex and tight folds that are overturned in the southern direction and are sheared by steep angle faults (Aadil and Sohail, 2014;Dai et al., 2022a;Dong et al., 2021b;Kazmi and Abbasi, 2008;Kazmi and Jan 1997;Riaz, 2022;Shah, 2009;Shah, 2022;Wrobel-Daveau et al., 2021). Several east-west gentle and broad folds are present in the western part, whereas strike suddenly changes in the eastern part towards northeast and the structures consist of broad synclines and anticlines are tightly folded (Hasany and Saleem, 2012;Huang et al., 2021;Kazmi and Jan 1997;Liu et al., 2021). ...
The current study aimed to evaluate potential of multiple source and reservoir rocks of Potwar Basin, Pakistan. This study presents palynological, geochemical, and petrophysical data from source and reservoir rocks of Eocene and Paleocene sequences of the Dhulian oilfield. A total of 34 well cutting samples from two wells and four fresh outcrop samples were studied. Results of total organic carbon and Rock-Eval pyrolysis of the Sakesar Formation sediments shows good to very good TOC contents, whereas the Patala Formation sediments from well A shows very good to excellent and very good TOC contents in well B. S2 values of both formations' samples showed fair to good generation potential. Both formations appear mature and have primarily type III and mixed type II-III kerogen with good gas-generation potential. Palynological analyses are in agreement with the pyrolysis data and showed that sediments have type III kerogen in the oil/gas window having excellent gas generation potential. Three kerogen assemblages were identified: palynomorphs, phytoclasts, and amorphous organic matter. Petrophysical analysis of the Chorgali Formation limestone showed an average porosity of ~10.6%, with an average water saturation of ~33.72%, and an average hydrocarbon saturation of ~66.28%, thus indicating average to good reservoir potential. The findings of this research will help and guide exploration and production companies in the Potwar Basin in terms of source rock organic richness and maturity.
