Patala Formation Research Articles

Petrological evaluation of changes occurring in organic matter sourced from Patala-Chichali sequence, Upper Indus Basin

This study focuses on the determination of organic matter (OM) concentration, thermal maturity assessment, and source rock quality of the samples from the Chichali and Patala formations. The TOC in the Chichali and Patala formations sediment samples ranged from 0.8% to 2.1% and 2.3% to 3.8% respectively, showing the sediments with different level of organic richness. The genetic potential varied from 2.4 to 17.1 mg/g, and 25.2 to 31.1 mg/g indicating the likely source rock quality. The Tmax, ranging from 306 °C to 432 °C, 413 °C and 430 °C indicating immature to mature OM. The HI values varied from 113 to 257 mg/g, 353 to 431 mg/g, OI ranged from 7 to 33 mg/g, 9 to 19 mg/g, revealing OM richness. PI assess the potential productivity of source rocks, ranged from 0.5 to 0.7, 0.6 of Chichali and Patala formations, respectively. The various geochemical properties of the Chichali and Patala formations exhibited their varying geological potential. These findings add to a better knowledge of the geological properties of the Upper Indus Basin and provide significant recommendations for hydrocarbon exploration and resource estimation.

Smectite Illitization Geothermometry of the Upper Indus Basin Hydrocarbon Source Rocks (Pakistan)

Abstract —Smectite illitization geothermometry has been used to assess the thermal maturity and hydrocarbon generation potential of the late Paleocene to early Eocene Patala Formation in the Upper Indus Basin. X-ray diffraction (XRD) detected illite, muscovite, quartz, kaolinite, chlorite, and calcite. Comparison between air-dried (AD) and ethylene glycol (EG)-solvated XRD patterns reveals the absence of discrete smectite and interstratified illite-smectite (I-Sm). Additionally, authigenic illite-2M1 indicates that the Patala Formation has entered the late-stage diagenetic zone or the low anchizone, which lies in the R3 illitization zone. Abundant SiO2 and Al2O3 in the Patala clay fraction indicate the substitution of tetrahedral Si4+ by Al3+ within the smectite interlayers. Likewise, the relative abundance of K2O to CaO and MgO indicates the exchange of K+ with Ca2+ and Mg2+ during smectite illitization. Scanning electron microscopy (SEM) reveals in situ growth of platy illite crystals that form within the R3 zone. Furthermore, the total organic carbon (TOC) of the Patala shale exposed in Tirah suggests a poor to good source rock. The absence of discrete smectite and I-Sm, combined with the detection of discrete illite in the Patala shale, suggests that hydrocarbon might have potentially migrated from the source to the reservoir rock during smectite illitization.

Litho- and biostratigraphy and hydrocarbon source-rock potential of the Jurassic–Paleogene strata in the Kala Chitta Range, northwestern Himalayas, Pakistan

In this study Jurassic–Paleogene strata were investigated to understand the litho- and biostratigraphic framework and hydrocarbon source-rock potential of various stratal packages. Biostratigraphic controls were used to establish the chronostratigraphic framework of Jurassic–Paleogene strata in the area. The Lower Jurassic (Hettangian) clastics saw an unconformity during the Sinemurian–Pliensbachian, while the Lower Jurassic (Toarcian)–Middle Jurassic (Bajocian) clastic–carbonate mixed strata is also separated by a Bathonian unconformity from the Middle Jurassic (Callovian) to the Upper Jurassic (Tithonian) carbonate sequence. The Upper Jurassic Oxfordian strata are missing, while the Upper Jurassic (Kimmeridgian)–Lower Cretaceous (Valanginian) glauconitic sandstone and clays are the conformable sequences. The Lower Cretaceous (Hauterivian)–Upper Cretaceous (Turonian) clastics is a conformable sequence that is separated by a Coniacian–Santonian unconformity from the Upper Cretaceous (Campanian) pelagic carbonates. The Cretaceous–Tertiary boundary is marked by laterites, while the Paleocene (Thanetian) sequence is represented by a shale- and sandstone-dominated sequence. The Paleocene (Thanetian)–Early Eocene (Ilerdian) siliciclastic–carbonate mixed sequence marks the last episode of Tethyan sedimentation. Total organic content (TOC), organic petrography and Rock-Eval pyrolysis (REP) techniques were used to evaluate the hydrocarbon source-rock potential, kerogen type and level of maturity of the hydrocarbons. The majority of studied samples show the occurrence of type IV kerogen. However, the Middle Jurassic (Callovian)–Upper Jurassic (Tithonian) carbonate sequence of the Samana Suk Formation, the Kimmeridgian–Valanginian Chichali Formation, the Paleocene (Thanetian) sequence of the Hangu Formation and the Paleocene (Thanetian)–Early Eocene (Ilerdian) Patala Formation confirms the Type III kerogen, poor–fair source-rock quality, immature–mature, gas- and oil-prone indigenous hydrocarbon occurrence in the region.

Microfacies shift in the Late Paleocene–Early Eocene Patala Formation in the Upper Indus Basin (Pakistan): Implications for development of the Ceno-Tethys Ocean

Field observations, petrography, and laboratory interpretations of the Patala Formation were utilized in an integrated petrologic study aimed at deciphering the genesis mechanism and controlling factors of the limestone/shale alternation during the mature development of the Ceno-Tethys Ocean in the Upper Indus Basin of Pakistan. To achieve this goal, the Patala Formation is categorized into four integrated microfacies (MM-I to MM-IV). Multiple cycles of transgression/regression are noted through fluctuations in eustatic sea level, controlled by climate and regional tectonism. Consequently, a deepening, upward retrogradation sequence was deposited on a carbonate platform of the Ceno-Tethys Ocean. The sediments of the Patala Formation exhibit a facies shift from a shallow-marine to a relatively deep-marine platform. It is indicated by the transition in fossils from shallow-marine green algae, trending towards a relatively deeper-shelf comprising benthic foraminifera such as Discocyclina, Ranikothalia, red coralline algae, echinoids (Echinothrix), and Alveolina, species. The deeper species possess robust shells adapted by organisms to maximize oxygen and light at greater depths. Additionally, mineralogical features, including gypsum (deposited in a lagoon within the platform) and pyrite (found in a deep slope toward a deep shelf), confirm deepening upward interpretations. Thermophilic dinoflagellates, thermal dissolution fragments, and hardground surfaces indicate a Paleocene-Eocene Thermal Maximum (PETM; in the lower part, ca. 56 Ma) of the Patala Formation, assigning a relative chronological age from the late Paleocene to early Eocene. These results highlight the joint influence of climate change, sea level rise, and continuous tectonic activity (associated with the Indo-Eurasian collision) on the pattern of sediment filling, and facies shift. Furthermore, the study contributes to understanding sedimentary environments, paleoenvironmental reconstruction, and paleotectonic evolution of the basin. This ideal case study provides a breakthrough advancement in globally comprehending the complex relationships between periodic autocyclic processes and aperiodic allocyclic events.

Kahi mélange complex in Kurram and Waziristan, NW Pakistan: An integrated approach for tectonic implications to India–Afghan suturing

The Kahi mélange complex in the Waziristan and Kurram sector (N–W Pakistan) is one of the several Neotethyan ophiolite–mélange complexes exposed along the westernmost margin of the Indian plate, preserving significant information on pre, syn and post–collision tectono–stratigraphic evolution of collision tectonics between the Indian plate and the Afghan block. It consists of highly dismembered ophiolitic and sedimentary units. Petrographic and field observations of mafic and ultramafic rocks within the ophiolitic unit, reveal a complete, but dismembered ophiolite suite similar to the Waziristan Ophiolite (WO) to its southwest. The sedimentary units consist of syn–orogenic deposits, turbidites and slope sediments of Campanian age as constrained by the Late Cretaceous radiolarians (Stichomitra communis Squinabol) and planktonic foraminifera (Rodotruncana Calcarata). From the structural point of view, the dismembered ophiolitic units represents the highest tectonic edifice. It’s overthrusting onto the Campanian sedimentary unit constraints the onset of the collision between the Indian plate and Afghan block to the Late Cretaceous. The subsequent obduction of combined ophiolite–sedimentary units over the brecciated Late Paleocene Lockhart Formation of Indian plate margin constraints the time of the end of the collisional stage. The unconfirmable deposition of the marine Patala Formation, Late Paleocene–Early Eocene in age, above the Kahi mélange complex documents the closure of Neotethys in the Early Eocene. In conclusion, our findings document that the Kahi mélange complex represents a typical polygenetic mélange formed by the superposition of two different dismembered units (the ophiolitic and the sedimentary units) coupled as a result of at least two tectonic events in a subduction–accretion setting related to the collision between the Indian plate and the Afghan block.

Integrated Interpretation of Eocene-Palaeocene Rocks in Potwar Basin, Pakistan: Implications for Petroleum Generation

This study demonstrates how an integrated geochemical and petrophysical analysis can be used to evaluate the petroleum generation potential of source and reservoir rocks. The Eocene and Palaeocene sequences of the Potwar Basin, located in the upper Indus Basin of Pakistan, were analyzed. Well logs and Schlumberger log interpretation charts were used for the petrophysical analysis of the Chorgali Formation's reservoir potential. Geochemical methods were applied to 34 well-cutting Sakesar and Patala formations samples. Results from Vitrinite Reflectance (VR) (%Ro) and Tmax data suggest that both formations have reached the peak of their oil generation window. The Sakesar Formation has a mean TOC of 1.88 wt. % and HI values of 375 mg HC/g TOC. The Patala Formation has a mean TOC of 3.33 wt.% in well A and HI values ranging from 2.4 to 369 mg HC/g TOC in well B, with a mean TOC of 3.52 wt%. Both formations have mixed Type II/III kerogen. The findings indicate that both the Sakesar and Patala formations possess good oil/gas-generation potential and may act as source rocks in the Potwar Basin. Petrophysical analysis of the Chorgali Formation shows an average porosity of 10.32%, water saturation of 36.14%, and hydrocarbon saturation of 63.85%. This indicates that the Chorgali Formation has an average to good reservoir potential. The research findings will aid exploration and production companies in the Fimkassar Oilfield.

Evaluation of mixed organic-rich carbonate and shale rocks of Meyal oilfield using an integrated palynofacies, geochemical and petrophysical approaches

This study integrated palynological, geochemical, and petrophysical analysis that maybe used to analyze petroleum rocks. Shales and sediments rich in carbonate are essential in assessing the geological history of source rocks for the generation of petroleum. This emphasizes the important role of carbonate source rocks on a global level. This study evaluated the source and reservoir rocks of Meyal oilfield, Potwar Basin. Twenty-five well cutting samples from two wells and four fresh outcrop samples were studied. Results of TOC and Rock-Eval of Sakesar Formation samples showed fair to good TOC, Patala Formation in well had very good TOC contents in well both wells. S2 values of both formations’ samples showed fair to good generative potential. Both formations lie in the maturity window having primarily mixed Type II/III and Type III kerogen with good oil/gas-generation potential. Palynological analysis also shows Type III kerogen in productive oil/gas window and in good agreement with pyrolysis data. Three forms of kerogen assemblages were identified: Structured and Bio-structured phytoclasts, opaque phytoclasts, and AOM. Petrophysical analysis of Chorgali formation showed average porosity ∼12.01%, average water saturation ∼37.71%, and average hydrocarbon saturation ∼62.28%, indicating average to good reservoir potential. Findings of this research will help and guide exploration and production companies.

1-D basin modeling, 3-D reservoir mapping and source rock generative potential of Balkassar oilfield, Potwar basin, Pakistan

This study presents geochemical, petrophysical and seismic interpretation and modeling data of source and reservoir rocks of Eocene and Paleocene sequences of Balkassar oilfield, Potwar Basin, Pakistan. Integrated approaches were applied to evaluate structure and various rocks i.e., Patala, Lockhart and Chorgali formations. Grid of eleven seismic lines, well logs, well tops and ten fresh rock cutting samples were used. TOC content of Patala Formation ranges between 0.25 − 1.16 wt. %, with S2 values 0.11–0.63 mg HC/g rock, thus indicating poor to fair hydrocarbon potentialwhich issupported by no distinct presence of hydrocarbon peaks in pyrolysis-GC pyrograms. Petrographic analysis showed dominant presence of vitrinitic Type III and inertinitic Type IV kerogen phytoclasts with minor amount of AOM. High abundance of reworked vitrinite and inertinite phytoclasts appear to have influenced the vitrinite reflectance data. Basin modeling predicts Lockhart Formation began oil generation at 10.30Ma age at depth 1557 m and reached peak generation at 8.43Ma age at depth 1802 m. Patala formation began oil generation at 10.56Ma age at depth 1472 m and reached its peak generation at 8.43Ma age at depth of 1768 m. 3D horizon mapping depicts that Chorgali formation is uniformly distributed and faulted from northwest corner.

An integrated palynofacies, geochemical and petrophysical analysis for characterizing mixed organic-rich carbonate and shale rocks of Dhulian oilfield Potwar Basin, Pakistan: Insights for multiple source and reservoir rocks evaluation

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.

Characterization of seismic anisotropy using azimuthal AVO analysis (AVAz) - An application case study in the deep and tight carbonate reservoirs from Potwar Basin onshore Pakistan

Reliable characterization of subsurface fractures information within the carbonate's resources plays a key role in reservoir description in terms of the storage and movement of fluid. Commonly, anisotropy information classifies heterogeneity in the rock fabric due to fractures, pores, and local stress variations. Amplitude Variation with Azimuth investigation examines azimuthal variations in the seismic amplitude information to provide useful information about fractures and anisotropy of a horizontally transverse isotropic (HTI).This paper presents modeling, analysis, and interpretation of Azimuthal amplitude variation with angles (AVAz) from 3D seismic and calibrate results with the wells data to extract fractures information in terms of fractures magnitude and orientations. We employed two most used data-driven alternate approaches 1) near-offset Rüger's equation and 2) azimuthal Fourier Coefficient (FC) for analyzing the AVAz responses in seismic data to estimate the fractures density and their orientations, and results are calibrated with the bore hole image data (FMI). These approaches proved practically convenient to quantify the azimuthal amplitude variations with two sets of AVAZ attributes. The results of AVAz modeling and analysis required good quality of input data. Before AVAZ modeling and attributes analysis, seismic data is pre-conditioned, and the data quality of the 3D seismic dataset is improved. Several qualitative and quantitative QC measures (e.g., comparison of angle stacks, AVAz analysis, cross-plots of correlation coefficients, and time shifts) are employed to ascertain the improvement of the health of the seismic data. Azimuthal AVA modeling helped to understand the azimuthal amplitude response due to anisotropy caused by fractures/stress. The predicted seismic response from the models is used to assess the sensitivity of AVAZ with the parameters of the anisotropic model. After the AVAZ modeling, the outcomes of the AVAZ attributes are generated using to 3D seismic and calibrated with the well data set to identify the anomaly of anisotropic gradient (Bani) and second Fourier coefficients (R2) by relating to fractures density or stress magnitude. These attributes helped to identify the amplitude variations with offset and azimuth in the deep inhomogeneous tight carbonate reservoir interval (Patala) of DS hydrocarbon field discovered in the north Potwar Basin, onshore Pakistan. High score of Bani or R2 observed at well location at the tight Paleocene carbonate (Patala formation) reservoirs exhibited the presence of fractures which is confirmed from the image logs (e.g., FMI).The results demonstrated that the studied formations exhibit significant heterogeneity due to the faults/fractures and stresses associated with the complex geological structure of the basin as well as variations in the rock fabric. Hence, accurate analysis of the fractures information from seismic data is quite useful not only in understanding the reservoir heterogeneity to optimize the production, but also in predicting the completion and development strategies that may be most effective.

Evaluation of organic matter in sakesar and patala formations in Southern and Northern potwar basin, Pakistan

The investigation of organic matter contents present in Eocene-Paleocene formations of Southern and Northern Potwar Basin, part of Upper Indus Basin Pakistan was conducted using geochemical and petrological techniques. The organic carbon content of Sakesar and Patala formations were evaluated using thirty well cutting samples from two wells, and results of both wells were compared for the first time. Patala Formation is known to be one of Potwar Basin's major petroleum bearing source rocks. Both Sakesar and Patala formations samples lie in early maturity (oil window) and peak of oil generation window for hydrocarbon generation, indicated by both vitrinite reflectance VR (%Ro) and Tmax data. Sakesar and Patala formations source rock properties shows good to very good generative potential. Sakesar Formation samples showed good TOC contents, ranging from 1.36-2.3 wt%, with 1.88 wt. % mean TOC and had HI values up to 375 mg HC/g TOC, however, Patala Formation also had good to very good TOC contents ranging from 2.65-4.2 wt% in well A and 3.1-3.9 in well B, with HI values ranging between 2.4-369 mg HC/g TOC. The samples have primarily mixed Type II/III kerogen and Type III kerogen. Results show that both formations have potential to produce hydrocarbons.

Geochemical evaluation of hydrocarbon generating potential and thermal stress experienced by Patala Formation, Salt Range, Upper Indus Basin, Pakistan

This study focused on the investigation of hydrocarbon potential, thermal maturity and ranking of the coal from the Salt Range in Pakistan. Four different mines located in different areas of the Salt Range were selected for sample acquisition. The samples were further processed and analyzed in laboratory using proximate analysis, ultimate analysis and Rock-Eval pyrolysis. Proximate analysis illustrate that coal of the Salt Range is of low rank because of low moisture content and high volatile material. The ultimate analysis indicates that the coal is immature with lower carbon contents. The coals have total organic carbon contents in the range of 36.45 to 48.68 wt.% and hydrogen index values between 277 and 445 mg HC/TOC indicate that the organic matter type is dominated by type II. Moreover, Rock-Eval pyrolysis parameters further support it as an excellent source rock having type II kerogen, oil-prone nature with some gas-prone character. These data suggest that the coal samples are in low conversion state and thermally immature.

An assessment of the source potential and reservoir characterization for tight gas exploration in the Subathu Formation shale, Himalayan Foreland Basin, Northwestern India

The Late Paleocene to Middle Eocene Subathu Formation shales in the prospective Himalayan Foreland Basin (HFB) were investigated to assess their source potential and reservoir characteristics. The organic-geochemical analysis of the investigated samples reveals that the total organic carbon (TOC) content ranges from 0.3 to 42.4 wt%, with an average value of 7.5 wt%. The visual kerogen assessment (VKA), the modified van Krevelen diagram and the HI versus Tmax crossplot indicate the prevalence of type III (gas-prone) kerogen. This is supported by the presence of significant amounts of vitrinite and inertinite group macerals, suggesting deposition in proximity to the source (e.g., swamp forest) in nearshore paludal (marshy) environments. The maximum pyrolysis yield temperature (Tmax) values range between 340 °C and 607 °C, suggesting immature to postmature gas generation stage. The vitrinite reflectance (Ro) values of the basal shale sequence range from 1.16 to 3.6 %, and their high maturity is attributed to their proximity to a major backthrust. The estimated hydrocarbon generation, migration, and retention data suggest a 91%–99% expulsion of hydrocarbons from the Subathu Fm shale. The bulk mineralogical data confirm the dominance of clay minerals (average 54.5%), which decreases up-section, where the younger shales have lesser clays and higher silica content. The kerogen type, richness and level of maturation along with the poor brittleness support a low fracability potential of the basal Subathu shales for tight gas production. A regional comparison is attempted with the Patala Formation in the Potwar Plateau of Pakistan.

Geochemical characteristics of coal seams within the Paleocene Patala Formation, Central Salt Range coal mines (Punjab), Northern Pakistan

Geochemical characteristics of coal seams within the Paleocene Patala Formation, Central Salt Range coal mines (Punjab), Northern Pakistan

Depositional and diagenetic constraints on the quality of shale‐gas reservoirs: A case study from the Late Palaeocene of the Potwar Basin (Pakistan, Eastern Tethys)

Unconventional shale‐gas reservoir assessment concurs numerous exploration challenges, often related to their complex lithology, which reflects secular changes in depositional environment(s) as well as spatially variable diagenetic overprinting. This study combines a range of methods (sedimentological, petrographical, CL‐microscopy, X‐ray diffraction, TOC (total organic carbon), TON (total organic nitrogen) and δ13Corg and δ15Norg stable isotopes) to address the controls of lithofacies, palaeo‐depositional environment(s) and diagenesis on the shale‐gas reservoir potential of the Late Palaeocene Patala Formation in the Potwar Basin of Pakistan. This formation records sediment accumulation in a shallow, mixed siliciclastic‐carbonate shelf environment. Sedimentological and X‐ray diffraction (XRD) analyses show that the formation is primarily composed of an alternation of carbonaceous, siliceous, calcareous and argillaceous mudstone lithofacies. Detrital assemblages, including grains of quartz, apatite, calcite, chlorite, as well as organic matter (OM) and clay minerals with auxiliary (authigenic) pyrite, dominate the formation. High terrigenous influx is represented by the abundance of siliciclastics and terrigenous OM. The δ13Corg and δ15Norg proxies reflect dysoxic to anoxic palaeo‐environmental conditions, which promoted preservation of mixed marine and terrigenous OM, a setting considered to be indicative for high shale‐gas potential. The organic‐rich siliceous and carbonaceous mudstone lithofacies are considered to be the most prospective intervals, while calcareous and argillaceous mudstones are considered least promising in terms of reservoir quality. Spatially variable eo‐, meso‐ and telo‐diagenetic features such as compaction, cementation, stylolitization, dissolution and re‐precipitation are superimposed upon the depositional fabric, which locally affected the reservoir quality of the Patala Formation. The results of this study strongly suggest that the organic‐ and quartz‐rich mudstone lithofacies constitute “sweet spots” whose occurrence in space and time may be traced to design a strategy for shale‐gas exploration in the Potwar Basin of Pakistan and in analogous settings elsewhere.

Detrital Zircon Provenance of the Cenozoic Sequence, Kotli, Northwestern Himalaya, Pakistan; Implications for India–Asia Collision

This study reported the detrital zircon U-Pb geochronology of the Cenozoic sequence exposed in Kotli, northwestern Himalaya, Pakistan, which forms part of the Kashmir foreland basin. The U-Pb detrital age patterns of the Paleocene Patala Formation show a major age cluster between ~130–290 Ma, ~500–1000 Ma and ~1000–1500 Ma, which mainly resembles the lesser and higher Himalayan sequence. However, the younger age pattern (~130–290 Ma) can be matched to the ages of the ophiolites exposed along the Indus–Tsangpo suture zone. In addition, two younger grains with 57 Ma and 55 Ma ages may indicate a contribution from the Kohistan-Ladakh arc. The detrital zircons in the upper Tertiary sequence show the increased input of younger detrital ages <100 Ma, with more pronounced peaks at ~36–58 Ma, ~72–94 Ma and ~102–166 Ma, indicating the strong resemblance to the Asian sources including the Kohistan–Ladakh arc, Karakoram block and Gangdese batholith. This provenance shift, recorded in the upper portion of Patala Formation and becoming more visible in the upper Tertiary clastic sequence (Kuldana and Murree formations), is related to the collision of the Indian and Asian plates in the northwestern Himalayas. Considering the age of the Patala Formation, we suggest that the Indian and Asian plates collided during 57–55 Ma in the northwestern Himalayas, Pakistan.

Subsurface Structural Interpretation of Missa Keswal Area, Eastern Potwar, Pakistan

Potwar Basin is although a hydrocarbon prolific basin but shows mixed scenarios regarding the success ratio of the wells. Several wells are producing good but a significant number of wells ended up with a great loss. Missa Keswal area is also a part of the Potwar Basin which was discovered in 1991. The main objective of this research is to find the subsurface structure of the Missa Keswal area with the help of seven seismic lines, 3-D modeling, and the correlation of five wells. Kingdom suite 8.8 is the main software used to delineate the subsurface structure along with some other software. Results indicate that the tectonic framework of the study area is mainly controlled by the Jhelum strike-slip fault and decollement layer i.e., Pre-Cambrian salt. Structural analysis shows that the study area bears NE-SW trending salt cored pop-up anticlinal structure bounded by major thrust fault and back thrust. Patala Formation acts as a source, Lockhart Limestone, Sakesar Limestone, and Chorgali Formation acts as a reservoir while fault surface (often acts a good conduit) and Neogene clays providing a potential sealing mechanism for entrapment.

Late Palaeocene to Early Eocene biostratigraphic framework from Upper Indus Basin, Pakistan, Eastern Tethys

This investigation resulted in the biostratigraphic framework of the Upper Palaeocene–Lower Eocene rocks from the Upper Indus Basin, Pakistan, Eastern Tethys. The Patala Formation of the Chinjana Nala, Surghar Range of the Upper Indus Basin, was selected for this purpose. Lithologically, the Patala Formation is composed of shale and limestone interbeds. Three different fossil groups – smaller benthic foraminifera, planktic foraminifera, and calcareous nanno‐planktons – are used to establish a biostratigraphic framework for the Patala Formation. The biozones recognized in this study include: (a) bathyal benthic biozones, BB1 and BB2 of the Late Palaeocene and Early Eocene, respectively; (b) planktic biozones, P4 and P5 of the Late Palaeocene, while E1 and E2 of the Early Eocene; and (c) Calcareous Nanno‐planktons biozones: the NP9, which is further divided into NP9a and NP9b of the Late Palaeocene and Early Eocene, respectively. These biozones have been integrated to identify the Palaeocene–Eocene (P–E) boundary interval by applying widely used biostratigraphic criteria (i.e.,Rhomboaster‐Discoaster[RD]‐assemblage of calcareous nanno‐planktons). In this study, we have considered the lithological interval between ChN/TP‐16 and ChN/TP‐17 as a marker horizon for the P–E boundary interval, which provided a basis for the correlation of locally established biozones with those established Tethys wide, that is, Pak‐DIV to part of Pak‐DVI correlated to SRX‐1 and SRX‐2, which are equivalent to BB1, P4, P5, and NP9a. Similarly, parts of the Pak‐DVI and Pak‐DVII are correlated to SRX‐3, which are equivalent to BB2, E1, E2, and NP9b within the study.

Estimation of Total Organic Carbon and Depositional Model of Paleocene Patala Formation Western Salt Range, Pakistan

In this research, we estimated the total organic carbon and presented a paleo depositional model of the Paleocene Patala Formation from the western Salt Range of Pakistan. Results shows, during the Paleocene period, the Patala Formation was settled in barrier-island or in back-barrier depositional environments. This evidence is on the basis of lithofacies analysis and TOC determination data from measured stratigraphic sections. According to lithofacies analysis and the TOC estimation of the Patala Formation, the carbonaceous shale deposits of Western Salt Range at Khairabad, Chitta Wahan, and the Kalri area were deposited in back-barrier marshes. In the study area, the Patala Formation 16 meter thick. Based on detailed outcrop investigation, we have divided the Patala Formation into five different lithofacies, i.e., grey shale, carbonaceous shale, sandstone, limestone, and a mixture of sandstone and shale facies. The TOC was measured with the help of a wet combustion titration method. Carbonaceous shale and grey shale lithofacies contain an average of 3.64 % and 1.39 % of TOC value, respectively. Results show moderate to very good TOC values in the shales of Patala formation, which indicates that Patala Formation in the Western Salt Range has a good source rock potential to generate hydrocarbon.

Mechanical and Elastic Characterization of Shale Gas Play in Upper Indus Basin, Pakistan

The organic-rich shale intervals of Patala Formation of Paleocene age may be considered as potential shale gas play in the Upper Indus Basin of Pakistan. Until now, seismic and elastic properties of the Patala shales are not investigated in detail necessary to declare it as shale gas play and to differentiate shale gas pay zone from the non-pay zone. Data of eight wells in which Patala shales were encountered at various depth levels from 2000 to 4300 m were deeply investigated for shale gas characterization. This shale fulfills the basic criteria of organic-rich shale with TOC ~ 0.5–5.8%, vitrinite reflectance (level of maturity) is 0.6–1.7%, average thickness 48 m. The brittleness index (BI) of this organic-rich shale was computed by using effective mechanical properties and mineralogy to define brittle zones in the shale intervals preferable for generating the fracture network. BI data points demonstrate that a large number of values fall in the brittle zone, whereas fewer values fall in the ductile zone. However, a certain number of values fall in the brittle–ductile transition zone. The quantitative comparison between different elastic and seismic properties derived from the wireline logs guide for the delineation of the pay zone from the non-pay zone in the organic-rich shale intervals.