Geopersia
Volume:12 Issue: 1, Winter-Spring 2022

The Ahwaz oilfield is located in the Dezful embayment of the Zagros fold-thrust belt in SW Iran. The oil source rocks predominantly with the argillaceous lithologies include the Kazhdumi, Gurpi, and Pabdeh formations as well as the basal part of the Asmari Formation. The concentrations of the major, trace, and rare earth elements (REEs) of these lithologies were determined using x-ray fluorescence spectroscopy (XRF) and inductively coupled plasma-emission/mass spectrometer (ICP-ES/MS), in order to infer the geochemical characteristics of the oil source rocks. The North American Shale Composite (NASC)-normalized major oxides displayed a positive anomaly in CaO, negative anomalies in other oxides and no anomaly in P2O5. According to the spider diagram of normalized trace element, there was enrichment in V, Ni, Cu, Cd, Pb, and Th values. In the NASC-normalized REEs pattern, the oil source rocks mostly display a smooth distribution shape, negative cerium anomaly, and slightly positive anomaly in the middle rare earth elements (MREES: Sm-Ho) values. The concentration of V, Ni, Co, and their ratios suggested a mixed marine and terrigenous source input. The ratios of redox-sensitive elements such as Ni/Co, V/Ni, V/V+Ni, Th/U, and Ce/Ce* suggested that the oil source rocks were mainly deposited under anoxic condition.

One of the main challenges facing the sustainable development of the Kalaleh region is the need for better management of this limited karstic fresh water resources. Kalaleh mountainous region in the north of Iran is drained by several karstic springs such as Zaw, Aghsoo and Yal-cheshme, having discharge rate of 20 to 2500 lit/s. The springs are mainly discharged from Lar, Tirgan, Mozduran karstic formations. In this research, the potential recharge mapping and catchment area of the major karstic springs have been investigated based on the groundwater balance and a GIS approach considering geological factors. In another part of the study, the determined primary catchment area by hydrogeological budget method was reconfirmed with geological method and the results were acceptable. Eight potential recharge contributing factors were evaluated using the GIS including drainage and slope, karstic features, lithology, land cover, precipitation and lineaments. The weights and the score of the factors were assigned based on aerial photos, geological maps, land use database and field verification. The different prepared layers were overlaid in GIS environment, and finally, the mean annual recharge rate of the karstic springs was determined which are in the range of 39-44% of the precipitation. Understanding the groundwater potential recharge zone of the Kalaleh watershed is important for management, proper utilization and future planning of water resources for sustainable management. The Lar formation has higher potential for karst development and infiltration than others. The effective karstic formations in recharging process in order of significance are Lar, Mozduran and Tirgan.

Unconfined compressive strength and tensile strength are important geotechnical characteristics whichare used for performance prediction and mix design in civil engineering projects. In recent years, theuse of waste materials as reinforcement elements such as glass, rubber and plastic waste increasedsignificantly. Nowadays, the use of polyethylene terephthalate (PET) has grown substantially for drinkbottles which is one of the most important environmental hazards. In the current study, the effect ofadding PET strips as reinforcement elements to a clayey soil has been studied by unconfinedcompressive strength and tensile strength tests. The compressive and tensile strengths of reinforcedspecimens with different PET contents (0%, 0.4%, 0.6%, 0.8% and 1% by the soil weight), lengths (12mm to 21 mm) and widths (3 mm and 6 mm) have been investigated. It was found that addition of thePET strips to the clay resulted in an increase in both the compressive and tensile strengths. The optimumPET content was dependent on the both width and length of the PET strips. The maximum UCS was321 kPa which observed in the specimen containing 0.8 % PET strips with 3 mm width and 18 mmlength. The maximum tensile strength was 33 kPa which observed in the specimen containing 0.6 % ofPET strips with 6 mm width and 15 mm length. The reinforced specimens containing I-shape PETelements exhibited a higher UCS value than that of the reinforced specimens with PET strips in mostcases which is may be due to increase of friction between the soil particles and the PET elements.

This paper aims to show the kind of corporations, Analytical Hierachy Process (AHP) for determining significant weights of evaluation criteria with "Technique for Order Preference by Similarity to Ideal" (TOPSIS) and "Simple Additive Weighting" (SAW) methods for ranking of geo-dataset for Mineral Prospectivity Mapping (MPM) of Cu in Anarak region, Central Iran. This operation was carried out by integration of remote sensing, geophysical, geochemical and geological data. The Anarak region has a high potential for copper mineralization because the studied district is located in the NW of the Central East Iranian Microplate (CEIM) that is an important ore mineralized zone in Central Iran. The integration approaches are complex, Multi-Criteria Decision Making (MCDM), and knowledge-driven methods that they named AHP-TOPSIS and AHP-SAW. In addition, there are three variant models of TOPSIS method including conventional, adjusted and modified. The AHP has been carried out on geological/alteration data, structural data, airborne geophysical data and stream sediment geochemical layer in the studied area. These data are classified by fractal modeling for the generation of geo-dataset layers to a relationship of copper occurrences in the Anarak region. Consequently, the produced MPMs by the AHP-TOPSIS and AHP-SAW have adequately matching and sufficient correlation with copper mines and main copper deposits/occurrences in the Anarak region.

Petrophysical evaluation of well log data of the Mid Cretaceous rocks (Upper part of the Sarvak Formation) were conducted for the Marun oil field. Rock and fluid volumetric indices, such as porosity type and distribution, water saturation, and lithology, were estimated from density, resistivity, neutron porosity, sonic and gamma ray logs. Petrophysical parameters including shale volume (Vsh), total porosity (PHT), effective porosity (PHE), water saturation (Sw), hydrocarbon saturation (Sh) and lithology were calculated. Matrix Identification (MID), M-N, NPHI- RHOB, NPHI- DT cross-plots indicated that the Sarvak Formation is mainly composed of carbonate lithology. Results also indicated that shale volume varies between 0.1% and 23.3%; total and effective porosities are between 0.8% and 47.2% and between 0.1% and 45.1%, respectively. Various primary and secondary porosities do exist in the Sarvak Formation. Majority of the porosities are preferentially developed in the middle part of this oil field. Water saturation is between 2% and 100%. The results reveal that the reservoir characterization of the Sarvak Formation is very variable and fluctuating from poor to good reservoir units. Apparently, Sw increase toward the center of the reservoir and eastward as well. This is probably in part controlled by fractures that are preferentially concentrated in the middle part of the anticline.

In petroliferous basins, integration of regional and local tectonics along with well data is used to understand the generation of geo-pressured variations in different lithological units. In the last 40 years, abnormal geo-pressured zones is the main challenge during hydrocarbons drilling in the tectonically complex Kohat Sub-basin, Sub Himalayas. The trapped fluid in post-Eocene strata generated the over-pressure zones and triggered drilling problems. The present study is an integration of data, by use of regional maps, seismic lines, and formation pressure using Eaton’s equation to understand the possible causes for the development of geo-pressured zones. Where, regional maps and seismic lines were employed for deciphering the regional and local tectonics, respectively. Porosity function and Normal Compaction Trend (NCT) curve were utilized for the identification of abnormal pore pressure zones (over-pressure and under-pressure zones). Three major stress regimes were interpreted. The results show that the mechanism of over-pressure zones developed as a combination of effective horizontal stresses, lithological variations and rapid sedimentation. The Normal Compaction Trend (NCT) line and porosity function indicated that the 1st and 2nd stress regime consists of major abnormal geo-pressured zones. Therefore, it is concluded that these stress regimes experienced more overburden pressure and fracture pressure. Consequently, it is suggested that the results of geo-pressure estimation from this work could be used for the appropriate mud weight during drilling in analogous tectonic settings.

The Early to Middle Devonian Padeha Formation in the eastern Alborz, is a thick terrestrial syn-rift succession of Early to Middle Devonian age. Sandstones in the basal 115 m, mainly of submature, mature and supermature in terms of their grain angularity, sorting, and matrix content. Most of the studied sandstones are characterized by their quartzofeldspathic nature, and are classified as quartzarenite, subarkosic and arkosic composition. Also, based on petrographic results, a paragenetic sequence is proposed for the sandstones, including three general stages. The sandstones have been examined using scanning electron and hot-cathodoluminescence microscopy to study the albitized detrital feldspars. Detrital K-feldspar is the major feldspar type that has been partly to albitized throughout the study sandstone. The textural variation is considerable, with vein-like, blocky, and patchy forms. Probable sodium sources for albitization include smectite to illite or chlorite transition, diabase sills, detrital albite dissolution, and replacement of detrital sodium plagioclases by authigenic minerals. From comparison with other basins worldwide, a temperature estimate of 75–130°C for the mesodiagenetic albitization is inferred, suggesting a burial depth of 2000-5500 m based on thermal burial model for the basin. The model suggests that the temperature at the base of the Padeha Formation did not exceed 150°C, constraining conditions for albitization.

In this study, thirteen surface samples were selected and investigated to characterize the oil shale thermal decomposition process from the Middle Jurassic Sargelu Formation in Lorestan province (Southwest Iran). The oil shale samples, for the first time, were studied using Differential Scanning Calorimetry (DSC) and the non-isothermal Thermogravimetric (TG-DTG) analysis with heating rates of 5, 10, and 15 °C/min. Thermo-oxidative decomposition of the Sargelu oil shale was occurred in three steps: (1) the thermo-oxidation of bitumen (according to the heating rate ranging from 210 °C to 401 °C), (2) the thermo-oxidation of the kerogen (between 365 and 560 °C), and (3) finally, the decomposition of calcite mineral (between 541°C and 815 °C). The thermal experiments show that the peak temperatures and reaction region intervals increased to greater temperatures by an increase in the heating rate. The activation energy parameter analyzed through the oil shale thermo-oxidative kinetics was evaluated using the ASTM E-698, Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) approaches. The mean activation energy calculated during low-temperature thermo-oxidative of the Sargelu oil shale is 127 KJ/mol. Compared to the Early Cretaceous Garau oil shale with the mean activation energy of 183 KJ/mol from the same locality (Shekarifard et al., in press), the Sargelu oil shale has lower activation energy. Eventually, kinetics analysis confirmed the occurrence of kerogen with (very) fast reaction rate in the Sargelu oil shale.

Due to the unsustainable groundwater utilization in the alluvial water resources, groundwater exploration in the karstic areas is the key concern for many developing countries. The purpose of this study is groundwater prospectivity modeling for recognizing karstic water-bearing zones in the southeast of Damavand Mountain, Iran. To do so, seven major geological and hydrogeolgical factors, including lithology, slope, distance from faults, vegetation, temperature, precipitation, and fracture density were considered. Then, all these thematic layers were weighted and combined using fuzzy logic and Analytical Hierarchy Process (AHP) operators by employing GIS software to generate four different models. Finally, the zoning map was classified into three classes (low, medium, and high), and the resultant maps verified by discharges of karstic springs in the study area. The results indicated that AHP-Fuzzy method has better performance than other models. According to this model, around 62.23% of the study area is classified as being at low and 15.72% as moderate groundwater potential while the remainder is categorized as high potential. The proposed model provides an appropriate approach to assess the groundwater potential for the study area, therefore, it can be concluded that RS and GIS coupling with other algorithms such as fuzzy and AHP are reliable tools in evaluation of karstic groundwater resource potential areas.

Imaging and inversion of potential field geophysics data permit the estimation of the source-property distribution in2D/3D space. In this work, the advantages and performances of a fast gradient-based imaging technique, known as the normalized full gradient (NFG), are examined to depict the source distribution in 2D space. In addition, a conventional Tikhonov norm-based inversion technique is used to estimate physical properties in 3D space. The functionality of these approaches are evaluated first for synthetic data sets, which involve three scenarios of a single source, a sloping source and a combination of them. Where the constructed sources and property distributions (i.e. density contrast and magnetic susceptibility) were compared. Then, algorithms were employed to the potential field data pertaining to the Shavaz iron-bearing deposit in Iran. Both methods have shown c accurately the centroid depth of all sources, but the boundary is better preserved by the inversion method for simulated sources and the real data set.. Iron ore occurrence is in the forms of hematite and magnetite lens which mainly have an elongation along a NW-SE strike, indicating the impact of the Dehshir-Baft fault on trapping the iron. It is worth pointing out that the inversion method led to more accurate information on geometry of the sought source by estimating density contrast and magnetic susceptibility values, but with higher execution time. In addition, the NFG algorithm takes less time to run, more sensitive to noisy data, and severely smeared-out the border of the source responsible for potential field anomaly.

In this investigation, the level of metals and metalloids (As, Sb, Co, Cr, Hg, Pb, Zn, Ni, V, and Ti) was determined in soil samples collected from the Sari Gunay gold mine surrounding area, west of Iran. A total of 38 soil samples were taken from the area close to mine, agricultural lands, and villages. Average concentrations of heavy metals in the soil samples were as follow: Co: 13.97 mg/kg; Cr: 95.79 mg/kg; Hg: 9.03 mg/kg; Ni: 55.05 mg/kg; Pb: 163.13 mg/kg; Ti: 0.42%; V: 103.29 mg/kg; Zn: 145.42 mg/kg. The mean concentration of metalloids was 106.53 mg/kg for As and 65.68 mg/kg for Sb. The results of EF and CF indicate that soil samples were very highly polluted by As, Hg and Sb, highly polluted by Pb, moderately polluted by Zn and V, and almost unpolluted by Ti, Ni, Co, and Cr. The Cd and PLI revealed that most soil samples in the gold mine surrounding area are extremely polluted. Based on the statistical analyses, including correlation coefficient analysis, principal component analysis (PCA), and cluster analysis (CA), the main source of the elements is the orebody itself and mining activities have increased the pollution degree. Arsenic, Hg, Sb, Pb, and Zn are related to gold mineralization veins and sulfidic minerals (e.g. stibnite, realgar, orpiment, cinnabar, galena, and sphalerite), while the other metals are originated from the oxide/hydroxide of iron in the supergene alteration zone and silicate minerals existing in host rocks.

Prediction of elemental concentrations is essential in mineral exploration as it plays a vital role in detailed exploration. New machine learning (ML) methods such as hybrid models are robust approaches infrequently used concerning other methods in this field; therefore, they have not been examined properly. In this study, a hybrid machine learning (HML) method was proposed based on combining K-Nearest Neighbor Regression (KNNR) and Random Forest Regression (RFR) to predict Pb and Zn grades in the Irankuh district, Sanandaj-Sirjan Zone.. The aim of the proposed study is to employ the hybrid model as a new method for grade distribution. The KNNR-RFR hybrid model results have been applied for the Pb and Zn anomalies classification. The hybrid (KNNR-RFR) method has shown more accurate prediction outputs based on the correlation coefficients than the single regression models with 0.66 and 0.54 correlation coefficients for Pb and Zn, respectively. The KNN-RF results were used for the classification of Pb and Zn anomalies in the study area. The concentration-area fractal model separated the main anomalous areas for these elements. The Pb and Zn main anomalies were correlated with mining activities and core drilling data. The current study demonstrates that the hybrid model has a substantial potential for the ore elemental distribution prediction. The presented model expresses a promising result and can predict ore grade in similar investigations.