Pakistan Journal of Geology (PJG)

The sedimentological study of the Lower Eocene Sakesar Limestone in Nammal gorge section, Western Salt Range, was carried out to elaborate the microfacies, diagenetic settings and reservoir potential. The Sakesar Limestone is widely distributed across the Salt and Surghar ranges. It mainly consists of massive and nodular fractured limestone with subordinate marls and chert in the upper part. The Eocene succession is only comprised of conformable Sakesar Limestone and Nammal Formation in Nammal gorge. The detailed study was conducted after measuring the vertical thickness of 18m section and the 6 six samples were obtained symmetrically. To give the detailed insight of sedimentological characteristics the well cuttings of Sakesar Limestone from well Pindori-01, were studied along with the un-stained thin sections to investigate the microfacies, diagenesis and reservoir potential. The well cuttings study revealed that the Sakesar Limestone is off white to dull grey calcite, moderately hard with cryptocrystalline to microcrystalline silica along with pyrite. Detailed field observations and laboratory investigations revealed that it contains Bioclastic wackstone microfacies. Neomorphism is present in various bioclasts. The presence of fractures filled with waxy leftover hydrocarbons makes it potential target for hydrocarbons. Petrophysical analysis shows an average hydrocarbon saturation of 85.5 percent in well Pindor-01 which confirms the huge reservoir potential of Sakesar Formation. Microfacies analysis indicates high lime mud and low faunal diversity which led towards the conclusion that the Eocene Sakesar Limestone was mainly deposited in semi restricted, low energy shallow marine shelf environment.

This study was a part of the applied field course at our department. The field work was done during the weekends for two weeks and it involves several locations including Bestari Jaya, Ulu Yam Dam, Paya Indah, Sungai (Sg.) Serai some open sand mining areas and others. The methods of sample extraction and handling were taught on site. Each group is divided into these respective locations for the study. For our group which is Group 4, the location assigned is Sg. Serai area. Equipment and item needed for this study was provided by the Geology Department. These equipment and item includes the water pump, the Hydro lab instrument, the cooler, and the sample bottle. The objective of this study was to study the geohydrology of the study area and to understand the environment of surrounding areas and its effect on the hydrology.

The petrographic analysis of Miocene sandstone at latitude 33° 45′ 00″ N to 33° 51′ 30″ N and Longitude 73° 35′ 36″ E to 73° 45′ 00″ E in the Himalayan fold and thrust belt was based on field observations and study of representative samples. At least 30 rock samples dislodged from outcrops for thin section preparations were soaked in blue epoxy resin before thin section grinding, then etched and stained using alizarin-red and potassium ferrocyanide for carbonate identification. The stratigraphic sections in the area were measured by tape-compass-clinometer method. Petrographic and textural data revealed that the quartz, feldspar, rock fragments, accessories, matrix and cement form the bulk composition of the rocks. The Miocene sandstones are lithic arenites and lithic greywackes. Further interpretation revealed the fracturing, flexure grain deformations, dissolutions, stylolitization, clay minerals anthogenesis, calcite and silica cementation during the diagenetic history of rocks.

The study area lies in the Sub-Himalayan fold and thrust belt of Northeastern Pakistan. The electrical resistivity soundings (Schlumberger array) in 24 locations were deployed using ABEM Terameter SAS 4000 (Sweden) with all paraphernalia in the order to explore ground water at considerable depth within formations. The 2D contour maps of apparent resistivity at 30 m, 60 m and 90 m spacings, transverse resistance and anisotropic contour maps, 2D and 3D maps of aquifer thickness and longitudinal conductance were compiled. The earth resistivity model was formulated by means of IPI2win software. The qualitative and quantitative interpretation indicates that the investigated area includes confined or semi confined type aquifers beneath sedimentary cover.