Effects of Diagenesis on the Reservoir Quality in the Upper Sands of Lower Goru Formation, Badin Block, Lower Indus Basin, Pakistan

The core samples of B member of upper sand reservoir rocks of the lower Goru Formation from three wellsof the Badin block were studied using thin section, XRD, and SEM techniques to investigate the diagenetic trends andtheir effect on reservoir quality. Microscopic study indicates that the B sand unit is mature with quartz as thepredominant mineral constituent with variable amount of feldspar and lithic minerals. The QFL plot indicates that mostof the samples are plotted in the field of quartz arenite, sub-litharenite and sub-arkose respectively. A few samplesbelong to the category of litharenite and feldspathic litharenite. The feldspars were partially to completely altered tokaolinite and other clay minerals. Coarse-crystalline or micro-crystalline calcite is the predominant cementing material.Bulk rock XRD analysis also confirms that the main mineral constituents of there samples are quartz and calcite invariable proportions. The undulose extinction and fracturing of quartz grains indicate that the area remained understress. Moreover, such fracturing is post-depositional and therefore is the product of late diagenesis. Scanning ElectronMicroscopic (SEM) images at 50 micrometer (μm) size show irregular type of fracturing within the quartz grains. Thislate stage fracturing of quartz has also generated various types of channels which may serve as secondary porosity. Thequartz overgrowth was observed in some samples due to late stage diagenesis. The micro-crystalline cement in the formof calcite is mostly present within the pores in fractured quartz. The results indicate that the diagenesis played asignificant role in improving the reservoir characteristics of B sand by increasing the porosity due to quartz fracturing,feldspar dissolution, alteration and quartz corrosion. Hence, better understanding of reservoir heterogeneities inporosity through diagenetic studies can be helpful in evaluating potential reservoir horizons for hydrocarbonaccumulation on spatial and temporal scales

INVESTIGATION OF GEOTHERMAL ENERGY POTENTIAL USING ELECTRICAL RESISTIVITY SURVEY AND CHEMICAL GEOTHERMOMETERS: A STUDY OF THE MANGHOPIR HOT SPRING KARACHI, SINDH PAKISTAN

Electrical resistivity survey and chemical geothermometers methods were used to find the geothermal gradient energy potential of the Manghopir hot spring which is located in Karachi, Sindh. Schlumberger electrode configurations were used to demarcate the two shallow potential subsurface aquifers. At various depths, three lithological units were encountered: alluvium, sandstone, and shale. The first thermal water aquifer lies below at the average depth of 10m and average thickness of 9 m lies in sandstone lithology of Nari Formation of Oligocene age. The second thermal water aquifer encountered at the average depth of 68 m and the average thickness of aquifer was 40.5m in sandstone lithology of Nari Formation. The surface water temperature was calculated with digital thermometer which shows the range in between 48 °C to 50 °C and subsurface temperature was calculated with the help of chemical geothermometers. The Na–K geothermometers indicate the subsurface equilibrium reservoir temperature in the range of 135.52 °C,125.54 °C, 172.964 °C and 184.08°C and the Na-K-Ca chemical geothermometers indicate the subsurface reservoir temperature 148.493°C. The Na-K-Ca geothermometers show a high temperature, but the reservoir temperature appears to be lower due to the mixing of sea water with the chemical composition of hot spring water within the subsurface aquifers

Exploration of Shallow Geothermal Energy Aquifers by Using Electrical Resistivity Survey in Laki Range Jamshoro district Sindh, Pakistan

Geothermal water is increasingly used around the world for its exploitation. Bulk electrical resistivity differences can bring significant information on variation of subsurface geothermal aquifer characteristics. The electrical resistivity survey was carried out in Laki range in lower Indus basin in the study area to explore the subsurface geothermal aquifers. The Schlumberger electrode configuration with range from 2 m to 220 m depth was applied. Three prominent locations of hot springs were selected including Laki Shah Saddar, Lalbagh and Kai hot spring near Sehwan city. After processing resistivity image data, two hot water geothermal aquifers were delineated at Laki Shah Sadder hot springs. The depth of first aquifer was 56 m and its thickness 38 m in the limestones. The depth of second aquifer of 190 m and with thickness of 96 m hosted in limestone. In Lalbagh hot springs two geothermal aquifers were delineated on the basis of apparent resistivity contrast, the depth of first aquifer zone in sandstone was in sandstone 15 m and thickness 12 m, while the depth of second aquifer was 61m and thickness was 35m. In Kai hot springs two hot water geothermal aquifers were delineated. The depth of first geothermal aquifer was 21m and thickness was 18 m and the depth of second aquifer was 105 m and thickness was 61m present in sandstone lithology. Present work demonstrates the capability of electrical resistivity images to study the potential of geothermal energy in shallow aquifers. These outcomes could potentially lead to a number of practical applications, such as the monitoring or the design of shallow geothermal systems

PETROGRAPHIC INVESTIGATION OF LIMESTONE OF THE LAKI FORMATION USED IN CONSTRUCTION SECTOR FROM JAMSHORO AND THATTA DISTRICTS, SINDH, PAKISTAN

Limestone belonging to the Laki Formation is well exposed at Nooriabad, Jhampir, and Makli Hills.  Representative samples of the Laki Formation limestone were collected from different locations such as Jamshoro, Bolhari, Makli Hills, and Nooriabad. The four crush plants i.e. Afridi Crush Plant and New Hazara Crush Plant (Makli, Thatta District), Shah Rahim Crush Plant and Bhatti Crush Plant (Nooriabad, Jamshoro District) were selected for sampling. The Petrographic investigation as per ASTM- C295-03 (1) was performed using standard thin sections. The megascopic and microscopic study results reflect no hindrance in using the studied limestone. For cement concrete, this limestone can be used for the low-strength concrete and aggregate base course and sub-base. Variation in lithology, stratification and non-homogeneity was observed, however, the aggregate from the New Hazara crush plant is found fractured in nature and therefore, its use as concrete material is not suggested. The studied limestone of all crushed plants does not show any potential for Alkali Silica Reaction (ASR) and Alkali Carbonate Reaction (ACR). Based on the present study, it is concluded that the studied limestone of the Laki Formation from the above-mentioned locations is suitable for construction purposes and industrial use. For cement concrete, this limestone can be used for the low strength concrete and pavement (sub-base & base coarse) as well as aggregate base course. In the stockpile of crushed aggregate on crusher plants, the chalky limestone was found to be less stable and less durable

Geochemistry and Petrogenesis of the Wadhrai Granite Stock of the Malani Igneous Suite in Nagar Parkar Area, SE Pakistan

The Wadhrai granite stock is a part of the Nagar Parkar Igneous Complex, an extension of the Neoproterozoic Malani Igneous Suite of western Rajasthan. It is occupied by a petrographically uniform granite comprising perthite, plagioclase, quartz, with small quantities of biotite, opaque oxides, titanite, and secondary minerals. The rocks are sparingly porphyritic and contain dykes of microgranite, aplite, and rare pegmatite. In the south-central part, parallel sheets and swarms of mafic dykes, and in the western part very fine-grained felsic sheets intrude the body. The granite is metaluminous to peraluminous and characterized by high silica (73–76 wt%), and alkalis (7–9 wt%), and low CaO (0.15–1.4 wt%), MgO (0.15–0.38 wt%), Th (7–12 ppm), and U (1–2 ppm). On geochemical discriminant diagrams, it classifies mostly as A-type (with rather high Y/Nb (8.6 to 2.4, average 5.2) and low Nb/Ga and Ce (typical of A2-type), but sparingly as I-type. Chondrite-normalized patterns show enrichment in LREE over HREE, and small negative Eu anomalies, whereas mantle-normalized spidergrams display higher LILE over HFSE, distinct troughs for Nb, Sr, P, Ti, and spikes for La, Ce, Nd, Sm and Tb. The granite magma was possibly derived from a tonalite-granodiorite-dominated crustal source. Based on the above-mentioned geochemical evidence, it is interpreted that the source rocks of the magma of the Wadhrai granite likely developed initially in a continental margin subduction setting and underwent partial melting in a continental extensional environment