The Middle Indus Basin of Pakistan characterized by various hydrocarbon reservoir units from the Jurassic to Eocene (Hussain et al., 2017; Banks and Warburton, 1986). The Middle Indus Basin is formed in response to continuous extensional forces during the Tertiary Himalayan orogeny therefore it is named as extra continental trough down-warp basins (Quadri and Shuaib, 1986).
Stratigraphic traps are gaining importance as possible hydrocarbon reserves and CO2 storage sites due to the world's increasing need for hydrocarbons. (Radwan et al., 2021; Wang et al., 2017). Stratigraphic traps in the MIB have substantial potential (Jadoon et al., 2020). One of the most important risk factors is understanding the correlations between reservoir porosity and permeability in these stratigraphic traps.
A very crucial phase in the evaluation and exploration of such complex siliciclastic objectives is the study of the reservoir quality (El-Gendy et al., 2022; Li et al., 2017). Sand composition, microscopic features, environments of deposition and diagnostic transformations influence reservoir quality (Bello et al., 2023; Yu et al., 2023; Radwan, 2022; Lai et al., 2018). Thus, the depositional environment and the subsequent diagenetic phases involve average detrital and antigenic associations (Niegel and Franz, 2023). In the efficacy of the tight sandstone reservoirs, the attributes of the pore system of the reservoir rock conspicuously depict the extents of hydrocarbon volume and water content and the flow capability. The main components of the pore system are porosity and permeability, as well as their interactions with regard to pore type, pore throat size, and distribution.( Lai et al., 2018; Anovitz and Cole, 2015). The digenetic processes that characterize the modification of the pore system in tight gas sandstones include compaction, cementation, and dissolution as outlined by (Radwan 2022) and (Higgs et al., 2007). Variations in digenesis of tight sandstone reservoirs are highly associated and dependent on several geological factors, which include; source, transportation, and depositional setting of sediments (Taylor et al., 2010). Hence, the successful exploration of tight sandstone reservoir depends on origin, depositional environment and digenesis precise assessment.
Geophysical well log data considered as convenient but indirect approach for the identification of lithofacies. The application of the well-log data for determination of lithofacies is a reasonable and efficient approach for the parts of the sequence that is non-cored or only partially cored sections, despite the uncertainty is much higher in comparison with the direct rock-core analysis. The analysis of well-log data has become common due to its effectiveness and continuity in providing required information.(Al-Mudhafar., 2017; Al-Mudhafar & Bondarenko., 2015; Nashawi & Malallah., 2009; Tang et al., 2004; Lee & Datta-Gupta., 1999). Petrophysical features interpretation on well logs recognizes and categorizes distinct lithofacies, employing statistical responses to build electrofacies (Serra & Abbott., 1982). however, it is important to remember that well-log data can be manipulated by white or heteroscedastic noises from sources, which depend on the depth such as temperature or confining variations in pressure Masoudi et al. (2017). Well-log signals are noisy and it becomes rather challenging to decipher precise lithofacies at a high resolution level. (Lindberg & Omre, 2014; Theys, 1991). Subsurface heterogeneity in lithofacies can impact practical subsurface applications, such as oil recovery productivity and CO2 migration, by controlling fluids in porous media (Krishnamurthy et al., 2017; Gershenzon et al., 2014; Alusta et al., 2011; Frampton et al., 2009; Kumar et al., 2005). It's crucial to divide a lithofacies group into the necessary categories. The interpretation of lithofacies commonly disregarded in practical applications, leading to erroneous estimation and planning during subsurface developments.
The present study attempts to delineate the detailed lithofacies analysis of Lower Goru Formation using the core data. The foremost objective for this study was to interpret depositional environment of Lower Goru Formation. Six cores were obtained in targeted reservoir to conduct detailed studies on reservoir characteristics, totaling 40.58 meters in length. Core intervals are mentioned in (Table 1) report that the stratigraphic traps contain considerable recoverable deposits (Jadoon et al.,2020). A number of researchers (Yasin et al., 2021; Qiang et al., 2020; Ali et al., 2019; Abbasi et al., 2018; Anwer et al., 2017) have work on stratigraphy and regional tectonic of lower Goru formation. There is no detailed research on an integrated core-calibrated strategy for analyzing possible sand intervals, depositional environments, and digenetic histories. (Berger et al., 2009) focused on the E sand interval of the Kadanwari gas field, examining the formation and origin of chlorites.
Numerous analysts have considered the relationship and contrasts between distinctive lithofacies, genetic advancement and reservoir quality of sandstone, which impact digenesis Heterogeneity and quality of the reservoir, particularly in terms of physical, chemical and Natural changes shift with profundity, temperature, and pressure fluid composition after deposition(Marghani et al., 2023; Aneeset al., 2022; Alzoukani et al., 2022; Ali et al., 2022; Akinlotan and Hatter, 2022; Bello et al., 2022; Boutaleb et al., 2022; Cui and Radwan, 2022; Nabawy et al., 2022;Radwan et al.,2022; Sabouhi et al., 2022; Duarte et al., 2021; Lawan et al., 2021a, 2021b; Li et al., 2021a,2021b; Wang et al., 2021; Xi et al.,2019 Morad et al., 2018).Moreover, the petrographical classification of Goru Sandstone as subfeldsarenite to sublitharenite, primarily deposited in transitional recycled orogeny, provides key insights into the provenance and diagenetic history of the formation. Such detailed petrographic analysis is instrumental in understanding the geological processes that have shaped these reservoirs over millions of years.
The novelty of this study lies in its comprehensive approach to the analysis of lithofacies in the Lower Goru Formation. By meticulously identifying and classifying nine distinct lithology’s, ranging from massive sandstone to pebbly sandstone, and grouping them into three facies groups (foreshore, shoreface, and offshore), this study provides unprecedented levels of detail in understanding this formation. Moreover, the conventional test methods, methodologies like the Scanning Electron Microscopy (SEM) used in the evaluation of porosity and permeability adds to the richness of the results. Also, the originality of this research lies in the identification of the depositional environment in the Lower Goru Formation. On this account, the study illuminates the detail of sediment transporting process and paleogeographical evolution of region by proposing a fluvial to tidal dominated delta front to shallow marine depositional environment. This holistic view is crucial for more accurate predictions of reservoir behavior and quality. This study not only contributes to the existing body of knowledge on the Lower Goru Formation but also sets a new benchmark in the comprehensive analysis of sedimentary basins, with significant implications for hydrocarbon exploration and reservoir quality assessment. Its multidisciplinary approach and novel insights mark a significant advancement in the field of sedimentology and petroleum geology.