Rudarsko-geološko-naftni zbornik

A Review on Glycerol-Based Drilling Fluids and Glycerine as a Drilling Fluid Additive

Ali Momeni, Seyyed Shahab Tabatabaee Moradi, Seyyed Alireza Tabatabaei-Nejad — Fri, 01 Mar 2024 00:00:00 +0100

A significant increase of energy demands all over the world and production decline from available oil and gas reservoirs have led the industry to invest in major offshore petroleum resources. However, drilling operations in offshore environments are usually restricted by environmental constraints. Therefore, recent studies are devoted to the development of environmentally compatible fluids with adequate technical properties. Glycerine is a non-toxic, lubricating, colorless, odorless substance with a higher density than water. Due to the properties of glycerine, it can be used as the base of drilling fluid to formulate synthetic-based fluids. This research aimed to review the studies on the applications of glycerine in the composition of drilling fluid. Based on the results, glycerine-based fluids can be considered as an environmentally compatible fluid with sufficient technical properties to replace other drilling fluids. However, there is a lack of experimental studies on the glycerine fluid properties for a reliable decision. For the application of glycerine fluids, an economic feasibility study is mandatory for both pure and crude glycerine. Also, the thermal stability of glycerine fluids is an important aspect, which should be covered in future research studies.

Upgrading and Surface Coating of Egyptian White Sand with Polymers and Silanes

Fri, 01 Mar 2024 00:00:00 +0100

Egypt is endowed with huge reserves of filler minerals, such as silica sand which form approximately 95% of the Earth's crust. The silica sand industry is used in many fields, such as pharmaceutical practices, chemicals, glass, ceramics, electronics, and photovoltaic industries. The aim of this study is to remove impurities from silica sand and apply surface modification processes to enhance its value for various industrial manufacturing applications. Various processing techniques, including classification, attrition scrubbing, magnetic separation, ultra-fine grinding and surface modification, were conducted throughout the study. The results indicated that attrition scrubbing to the classified size fraction of -0.6 + 0.1 mm was capable of reducing the iron concentration from 0.068% to 0.045%. Utilizing the Box-Behnken design, the optimal conditions for magnetic separation were identified, resulting in a decrease in iron content down to 0.012%. Simultaneously, the silica content increased from 99.05% to 99.76%. The results of ultrafine grinding using an attritor mill revealed that a grinding time of 2 hours is sufficient to reach a size suitable for the coating process. Surface modification of the produced ultrafine sand was conducted using polymers and silanes. The treated sand was characterized using SEM, zeta potential, adsorption density, and FTIR measurements. Notably, hydrophobicity increased, accompanied by an increase in particle size. Simultaneously, the surface becomes flatter, indicating the formation of a thin layer. Consequently, the coated sand proved to be a satisfactory material that met the criteria to be used as a filler in coating and paints.

Two-stage palm kernel shell washing with water and acetic acid as preparation of co-firing system with coal

Fri, 01 Mar 2024 00:00:00 +0100

Palm kernel shells (PKS) were washed with water and glacial acetic acid (CH₃COOH) gradually to prepare them for co-firing with coal. They were then torrefied at 450ºC for one hour. Washing was done to reduce the concentration of ash and alkaline oxides, which would reduce the chance of slagging and fouling. The research was conducted considering that information about washing the PKS with acetic acid and then having them torrefied is very limited and unclear. The results showed that washed and torrefied PKS had better characteristics than those of raw PKS or PKS washed with water. PKS that is washed with acid, torrefied and then blended with coal has low slagging and medium fouling tendencies. However, based on ash fusion temperature, the inclination towards slagging and fouling is high under reducing conditions and medium under oxidation conditions.

Assessment of ultra-low frequency (ULF) geomagnetic phenomena associated with earthquakes in the western part of Java Island, Indonesia during 2020

Fri, 01 Mar 2024 00:00:00 +0100

Ultra-low frequency (ULF) geomagnetic analysis is a robust method for earthquake (EQ) forecasting. We conducted a simultaneous study of EQ precursors around the western part of Java Island in 2020 using wavelet transform (WT) and detrended fluctuation analysis (DFA) methods. ULF geomagnetic data (March to December 2020, 16:00–21:00 UTC or 23.00–04.00 LT) from Lampung Selatan (LPS) geomagnetic station were used to assess the precursors. We analyzed four EQs with an epicenter distance (R) of around 100 km from LPS station and a magnitude (M) greater than 5 Mw. We analyzed changes in the S_Z/S_G values and α values from the WT and DFA analyses against the threshold (µ±2σ) to identify anomalies related to the EQs. The result showed that S_Z/S_G anomalies occurred simultaneously with a decrease in α values several weeks prior to probable source EQ when there was a very low geomagnetic activity (Dst ≤ -30 nT). The Mw5.4 (07/07/2020) EQ might be the main source that led to the appearance of the precursor since it had the highest magnitude and K_LS values compared to others. The combined WT and DFA results showed anomalies 1.5–13 weeks before the Mw5.4 (07/07/2020) EQ. The results suggest that WT and DFA are suitable methods for detecting EQ precursors but more work is needed to link the precursors to specific EQs.

Comparative Analysis and Evaluation of the Conversion Formula for Rebound Number of Schmidt Hammer Test and Unconfined Compressive Strength Test – Case Study: Andesite Rock Slope in Graha Puspa, Lembang Fault

Antonina Pri Martireni — Fri, 01 Mar 2024 00:00:00 +0100

The Unconfined Compressive Strength (UCS) test is one of the most common methods for determining the rock material strength value. However, the size and complexity of the instrument do not allow UCS testing to be carried out in the field. The UCS value can be estimated in the field by converting the rebound number using the Schmidt hammer test. This research aims to carry out a comparative analysis and evaluation of the conversion formula for rock compressive strength values resulting from the Schmidt hammer test and UCS test in a case study of andesite rock slopes at Graha Puspa, Lembang Fault, Bandung, Indonesia. Rock hardness testing was carried out using the Schmidt hammer test on five segments at Graha Puspa. UCS testing was carried out using a compressive strength machine on four samples in Graha Puspa. The test results show a rebound number value ranging from 31.67 - 45, while the UCS test results show a value range of 134.96 – 171.60 MPa The results of the previously published empirical equations differed considerably from the results of the UCS tests on rock samples in the laboratory when estimating the UCS values. From this evaluation, this research proposed formulation development of andesite rock formulation in the Lembang Fault area. However, UCS testing on more samples is highly recommended in order to obtain a compressive strength conversion formula that is more suitable for the case study at this location.

Implementation of flotation to recover lead and barite from Komsheche Mine jig tailings

Fri, 01 Mar 2024 00:00:00 +0100

With the increase in the basic metal prices, including lead, in the global markets, the processing of this precious metal, particularly for low-grade deposits, has a high economic justification. Investigating the extraction of lead minerals, including galena which is one of the minerals associated with barite, is considered one of the products of barite by-products. The purpose of this research was to study on the potential of producing high-grade barite, and recovering lead concentrate as a by-product from the jig tailings of the Komsheche barite mine. The prepared sample was subjected to mineralogical studies, and the obtained results indicated that the sample contains barite, iron hydroxides and galena as the dominant minerals and the degree of liberation was 90-95% in the size of 100 microns. The work index of the sample was obtained by the standard bond ball mill which was 8.72 kWh/t, indicated that the sample was not hard. The lead and barite grades in sample were 0.34% and 64.83%, respectively. Considering the high specific gravity of lead and barite, the processing tests were carried out in 2 stages of primary pre-processing using Mozley multi-gravity separator and then enrichment by flotation approach. After the end of the Mozley tests, the grade of lead reached to 0.6%, some fines were removed, and the classified sample was prepared for the next stage, flotation. At the end, the grade of lead increased from 0.6% to 53% with a final recovery of 73.65% and separation efficiency was 73.48%. Also, the specific gravity and grade of barite reached from 3.9 g/cm³ and 67% to 4.4 g/cm³ and 95%, respectively. These values are remarkable and meet the needs of the industry.

The influence of head strap elasticity on the protective properties of filtering facepiece respirators

Fri, 01 Mar 2024 00:00:00 +0100

The level of occupational respiratory diseases among workers in the mining, machine-building and metallurgical industries remains high. The most common occupational respiratory disease is pneumoconiosis, which is the result of the long-term inhalation of dust. It is possible to minimize the impact of dust on the workers and eliminate such diseases in the future due to the use of filtering mask respirators designed to reduce dust infiltration into the space under the mask. For this purpose, the choice of the type of elastic bands of filtering mask respirators has been substantiated by the geometric shape and tension forces that can ensure a permissible level of leakage of contaminated air into the breathing zone of the respirator during its use. A mathematical model has been developed to describe the influence of parameters of elastomeric headgear on the protective properties of the respirator. The dependence of the change in the residual tensile strength of the elastic bands of the headband has been established, and the dependence of the volume of air suction on the area of the elastic straps at the corresponding tension force has been determined. Using the model, the dependence of the volume of polluted air inflow on the area of the elastic straps at the corresponding tension force has been estimated. The design of the innovative inserts has been offered, which makes it possible to control the tension of the elastomeric head straps of the respirator to visualize the weakening of the pressure forces responsible for maintaining a tight fit.

Accurate prediction of drill bit penetration rate in rock using supervised machine learning techniques base on laboratory test data

Fri, 01 Mar 2024 00:00:00 +0100

Knowing the rate of penetration of a drill bit in rocks is among the most important parameters in their behaviour measurement. However, the direct measurement of ROP in rocks is a high-cost and time-intensive process. Therefore, obtaining the ROP parameter through a method other than direct measurement can be very useful and effective. Predictive machine learning methods are among the strong and precise techniques for the indirect measurement of ROP. To this end, 492 samples were tested under different UCS, µ, WOB, and conditions to obtain the corresponding ROP. To achieve an accurate model, three methods of linear regression analysis, lasso regression, and ridge regression were compared in terms of prediction accuracy. These models were compared through performance criteria of the prediction process and error-based charts. The performance criteria were measured using three measures: mean absolute percentage error, D-squared pinball score, and mean Poisson deviance error. For the MAPE index, the Lasso and Ridge models performed the best with values of 0.2557. Concerning the D²PS index, the linear regression model and Ridge performed better with values of 0.4083 and 0.4025, respectively. Finally, for the MPDE index, the Ridge model provided a more accurate performance with a value of 0.0105. For a better comparison, an objective function was created and calculated by combining these three indicators. The results showed the best rank for the Ridge model with an estimated value of 659.475. Finally, it was concluded that the Ridge model is a reliable and accurate model for predicting the ROP.

Impacts of Ammonium Sulfate Leaching on Ion Adsorption Rare Earths and Soil Mechanical Properties

Amirul Asyraf Mohd Hamka, Meisam Saleki, Zohreh Nabavi, Hesam Dehghani — Fri, 01 Mar 2024 00:00:00 +0100

In-situ leaching (ISL) has gained prominence as a non-destructive method for rare earth element (REE) extraction, particularly in regions like China. However, concerns over the environmental impact and soil stability due to ISL activities have surfaced following a landslide incident. This article distills the essence of a comprehensive research endeavor that delves into the effects of ammonium sulfate ISL leaching, employing concentrations of 0.05M, 0.1M, and 0.5M, on soil mechanical properties. The study encompasses physicochemical, physical, and mechanical tests, unveiling substantial alterations in shear strength, cohesion, angle of internal friction, zeta potential, liquid limit, plastic limit, and plasticity index following leaching. XRF and XRD analyses reveal the presence of REEs and distinctive mineral phases in the soil samples. Overall, ISL induces a weakening of the soil, raising concerns about potential slope failures and emphasizing the need for a deeper understanding of ISL's impact on soil properties in the context of REE mining.

Influence of Confining Materials on Detonation Parameters of ANFO Explosive

Vječislav Bohanek, Muhamed Sućeska , Ivana Dobrilović, Paulo Pleše — Fri, 01 Mar 2024 00:00:00 +0100

Due to the low manufacturing cost and ease of handling, ammonium nitrate-fuel oil (ANFO) is one of the most popular mining explosives. ANFO explosive is a typical representative of non-ideal explosives, which means that its detonation properties are strongly dependent on the charge diameter and the existence and properties of the confinement. In this work, the effect of different confining materials on the detonation properties of ANFO explosive is studied experimentally, and by hydrocode simulation by varying charge diameter, and the type and thickness of the confining materials. The results show that, along with the diameter of the charge, density and thickness of the confining material have a key impact on the detonation properties. An empirical confinement model, applicable in the range 0.3 < m_C/m_E < 15, is proposed. The model enables the estimation of detonation velocity of confined ANFO charges with a mean absolute percentage error (MAPE) of 14.25%.

Alluvial-lacustrine-marine complex of Mount Medvednica: the early syn-rift deposition and palaeogeography (Early to Middle Miocene, North Croatian Basin)

Davor Pavelić, Marijan Kovačić, Davor Vrsaljko, Radovan Avanić — Fri, 01 Mar 2024 00:00:00 +0100

Mt. Medvednica belongs to the western part of the Neogene rift-type North Croatian Basin that occupies the south-western Pannonian Basin System. The Lower to Middle Miocene continental to marine sedimentary complex was studied on Mt. Medvednica in order to interpret the early syn-rift depositional environment and reconstruct palaeogeography of the North Croatian Basin. Based on facies analysis, deposits are grouped into 16 facies based on their lithological characteristics. Six of the facies belong to the alluvial environment that is characterized by coarse-grained bedload siliciclastics. Nine facies are of lacustrine origin. They comprise: a) limestone of shallow lake carbonate bench with silty coal of vegetated marsh, b) deep lake and prodelta marl with sand and conglomerate intercalations deposited by gravity flows, and c) coarse-grained Gilbert-type delta conglomerate. The lacustrine deposits compose a transgressive-regressive sequence. The studied succession ends by facies of calcareous silt intercalated by conglomerates. These deposits belong to the marine offshore to prodelta as the consequence of establishment of the connection to the sea. The deposition was strongly controlled by allogenic factors, such as synsedimentary tectonics, climate, eustatic sea level changes and explosive volcanic activity. The alluvial deposits of Mt. Medvednica are the oldest syn-rift deposits and belong to the large alluvial plain that probably covered the entire North Croatian Basin in the Ottnangian and the Karpatian. These deposits are overlain by the lower Badenian lacustrine deposits, but the question of the existence of one large or several small lakes in the early Badenian North Croatian Basin remains open.

Multivariate Data Analysis to Assess Groundwater Hydrochemical Characterization in Rawadanau Basin, Banten Indonesia

Fri, 01 Mar 2024 00:00:00 +0100

A multivariate statistical technique of principal component analysis (PCA) and hierarchical cluster analysis (HCA) has been applied to identify and classify the various water sources that comprise the Rawadanau Basin. The data collection includes 60 samples taken during the dry (29 samples) and the rainy season (31 samples) in tropical regions. Sources of sampled water include dug wells, rivers, cold springs, and hot springs. Water chemistry measurable variables include field data (T, pH, EC), major ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^-, HCO₃^-, SO₄^2-), SiO₂, Fe_total, Mn, and stable isotopes of water (d²H, and d¹⁸O). The correlation of the concentration of water chemistry shows changes in the rainy season to Fe_total and Mn. Interpretation based on HCA using the dendrogram based on the chemical elements of water produces two clusters. Cluster A reflects an unconfined aquifer and bicarbonate type. Meanwhile, cluster B is a chloride type from the confined aquifer and does not change in different seasons. The PCA results show that the three-component matrix accounts for 86.12% of the data structure describing the Rawadanau Basin water sources that volcanic rocks affect and strongly correlate with Na⁺, K⁺, Ca²⁺, and Mg²⁺. PC1 has a high positive value for hydrochemical composition, indicating that lithology influences the kind of water. PC2 has a positive value for the stable isotope (d¹⁸O and d²H), meaning it is the main water source in Rawadanau. PC3 has a positive value for elevation and a negative for longitude, indicating a recharge area influenced by geological factors and is correlated with geothermal influences and volcanic rocks. This multivariate analysis can identify components and clusters of hydrochemical variables that have not been determined in previous studies.