نشریه مهندسی منابع معدنی
سال نهم شماره 1 (بهار 1403)

The initial model, Jacobian matrix, Frechet derivatives, and digital look-up tables are essential components in most time-domain electromagnetic (TEM) data modeling methods in layered earth. Computations of these components in the modeling process are time-consuming as their determinations need to use iterative operations. Zohdy introduced an alternative method for the rapid inversion of direct current (DC) resistivity data obtained using the Wenner and Schlumberger electrode configurations. The methodology allows for the inclusion of a flexible number of layers, which are chosen in conjunction with the initial model based on the data-derived knowledge, and avoids large and iterative calculations of Jacobian matrix and Frechet derivatives. This paper presents an endeavor to enhance the outcomes of TEM data modeling or inversion utilizing the Zohdy's technique through the elimination of the look-up tables. In this study, various synthetic models of stratified geological formations are examined using the the above-mentioned methodology. The modeling findings demonstrate robustness even when 5% and 10% noise levels are entered into the dataset. Hence, this approach can be considered as a worthy method for TEM data inversion accompanying some levels of noise in the data.

With the extraction of surface minerals and the depletion of their reserves, the exploration of deeper deposits has become a pressing consideration. Among the geophysical techniques available for such exploration, magnetometry stands out. Proton magnetometers, the prevailing instruments in terrestrial magnetometry, are characterized by their high cost, high weight, and large size. Moreover, their low sampling rate necessitates prolonged and consequently costly field operations. However, the advancement of Micro Electro Mechanical System (MEMS) sensors, which are both lightweight and cost-effective and possess high sampling rates and satisfactory sensitivity, has garnered significant interest. In this research, one such MEMS sensor was deployed and employed in the examination of a small iron deposit located in Western Iran. Then, the findings from these measurements were compared to those obtained using a proton magnetometer. The comparison reveals a substantial difference in efficiency. Magnetometry with MEMS sensors over the selected deposit took approximately 8.5 hours, whereas the survey with the proton magnetometer on the same profiles spanned around 44 hours. In addition to the time savings, the application of MEMS sensors led to a remarkable reduction in operating costs, by up to fivefold. On the other hand, due to the small size of this magnetometer, by placing it in a handbag or backpack of the operator, it is possible to carry out the magnetometer survey without any problem of dealing with the opponents and to prevent the postponement of the field magnetometer operation.

Separation and mapping of alteration zones is of special importance in the exploration of porphyry copper types. In order to highlight these alteration zones, remote sensing techniques have been applied. Zafarghand region is located in the southeast of Ardestan and northeast of Isfahan. Based on the division of geological structural zones, it is located in the Central Iran zone and also in the middle part of Urmia-Dokhtar magmatic volcanic arc. In this area, there are different alteration halos, including phyllic, potassic, propylitic, argillic, and slightly siliceous. In this study, argillic, phyllic, propylitic, and clay alterations have been identified using ASTER sensor images. Moreover, LANDSAT 8 images have been employed to identify clay and iron oxide alterations. In this regard, after performing the necessary pre-processing, methods of False Color Combination (FCC), Band Ratio (BR), Least Squares-Fit (LS-Fit), Matched Filtering (MF), and Principal Combination Analysis (PCA) were applied to reveal the zones containing these alterations. Among the applied methods, the LS-Fit and MF in Aster images, as well as the BR method in both images, and the PCA method in Landsat 8 have brought good results.

Well-testing is the analysis of reservoir and well behavior based on time. Obtaining the true value of changes in reservoir parameters plays a major role in creating an accurate and current model of the reservoir. The most crucial factor in achieving this objective is pressure, which is determined by a downhole pressure gauge. Operational issues and additional expenses are brought on by the use of pressure gauges at the well's bottom for the employer company. Surface well testing, which installs flow and pressure measurement devices at the wellhead, is another approach to well testing. The benefits of this technology include a significant cost reduction, ease of installation and data collection, easier operations, reduced risk, the ability to collect data for extended periods of time, and the ability to determine the impact of borders in large reservoirs. The difficulty of calculations and the insertion of errors as a result of the impact of well-column circumstances on the recorded data are the method's most significant issues. In this study, using Pipesim software, data obtained at the surface of a well located in a conventional undersaturated oil reservoir is converted to bottom-hole data, then analyzed, and finally, the properties of the reservoir are obtained. In comparison to the conventional well test method, the results demonstrate that the surface well test method can accurately forecast permeability, skin, productivity index, average pressure, and reservoir radius with error rates of 6.2, 17.3, 4, 7, and 13.3%, respectively.

Accurate simulation of geometrical properties of fractures is an important goal in rock engineering. One of the most capable methods for simulating the random nature of geometrical properties of fractures is Discrete Fracture Network (DFN) random modelling, which presents the heterogeneous nature of fractured rock mass with statistically defined geometrical properties. Up to now, all properties of fractures such as location, shape, orientation, size (persistence), spacing, and opening of joints have been simulated and applied in 3D DFN modelling. In this research, a statistical solution based on Kernel’s non-parametric distribution is used for simulating roughness. Through this method, even those geometric properties of fractures which do not have their own specific distribution functions can be simulated. After simulating the roughness value, the roughness geometry should also be simulated in a way that evokes the roughness value. Therefore, in order to simulate the surface of fractures in this research, the DRS method is applied in 2D and then, developed into 3D. At the end, simulation of discontinuity’s roughness is added as a separate package to DFN-FRAC3D computer program. DFN-FRAC3D computer program, as one of the most capable tools in this field, is able to develop a 3D fracture network block model by using the surveyed data and then simulating geometrical properties of the fracture; thus, by applying the results of this research in this compute software, all geometrical properties of fractures can be simulated. Finally, in order to explain the results of this research, outcomes of DFN-FRAC3D computer program for both with and without applying the roughness property on DFN are compared.

This article reports on a molecular dynamics simulation-based research that investigates the adsorption of sodium oleate (NaOl) on the of the highly hydrophilic 001 hematite surface in froth flotation and its effect on the mineral's wettability properties. The molecular dynamics simulation was conducted using LAMMPS. The wettability properties were evaluated by comparing the thermodynamic characteristics of two surfaces, one net and the other coated by the collector. Surface energy, center of mass location of water molecules, water density in contact layers and adjacent to the surface, and fluid permeability coefficient were used as indicators of wettability. The simulation results showed that the 001 surface of hematite is highly hydrophilic due to strong electrostatic interactions and feasible hydrogen bond formation sites. However, with the adsorption of the collector, the surface became hydrophobic due to a sharp decrease in surface tension, reduction of intermolecular interactions, and loss of hydrogen bond formation sites. The results confirm that the selective absorption of the collector on the hematite surface enables its floatability.