<abstract xmlns="http://www.w3.org/1999/xhtml">

The rapid drop in the penetration rate or failure of the drill bit during the drilling process delays the drilling process. In our investigation, the ‘<italic>in situ</italic>’ drilling parameters were monitored during the drilling process along with the roller cone drill bit, which is suitable for drilling in soft rock formations (IADC 136). The drill bit was thoroughly examined to determine its damage and wear occurred during drilling along with decreasing penetration rate. The modern and standardised investigation methods were used to analyse the rock materials and the micro- and macro-structure of the materials of the roller cone bit. The analyses were performed by means of optical and electron microscopes, simultaneous thermal analysis of the steel materials, analysis of the chemical composition of the materials of the drill bit and determination of the geomechanical parameters of the drilled rock. The resulting wear, localised fractures and cracks were quantitatively and qualitatively defined and the parameters were correlated to the drilling regime and the rock material. The results of our investigation of the material of the roller cone bit can serve as a good basis for the development of new steel alloys that can withstand higher temperatures and allow effective drilling without structural changes of the steel material.
</abstract>

Characterisation of the Wear of the Roller Cone Drill Bit Caused by Improperly Chosen Drilling Regime

<abstract xmlns="http://www.w3.org/1999/xhtml">

In geotechnology and mining, tools and equipment interact with aggressive geological material, causing the wear of these components. For this reason, it is important to determine the rate of abrasivity of individual geological materials, depending on the type of interaction with the tool. Various abrasivity tests have been developed in laboratories. Some of them are general, while others are special. What they all have in common is that they attempt to determine the abrasivity of rocks or soils in relation to the wear of the test specimens. This article gives an overview of the laboratory test methods for assessing the abrasivity of geological materials, which are useful in the field of geotechnology and mining engineering. General and special abrasivity tests are presented in detail. The aim of the article is to present existing laboratory tests to assess the abrasivity of rocks and soils, based on which further investigations of wear can be considered as part of a comprehensive approach to this tribological problem. Understanding of the wear mechanisms is the basis for the development of wear-resistant tools and models for predicting the tool life.
</abstract>

Laboratory Test Methods for Assessing the Abrasivity of Rocks and Soils in Geotechnology and Mining Applications

<abstract xmlns="http://www.w3.org/1999/xhtml">

In this article, we report the mineral chemistry and petrographic features of charnockitic exposure of Iboropa within Precambrian Basement Complex of Nigeria. The mineral assemblages are pyroxene, plagioclase, biotite, hornblende, alkali feldspars, microperthite, quartz and ilmenite, with apatite occurring as accessory mineral. Apatite occurs in abundance as euhedral crystals. Orthopyroxene observed is strongly pleochroic and has numerous microfractures, and it is hypersthene (En45Fs54Wo1) with low TiO2 and MnO, having extremely low percentage of CaO. Hypersthene is mantled by a complex corona of amphibole, and the amphibole is hornblende with a chemical formula: (K,Na)(Ca,Fe)2 (Fe,Mg,Al,Ti)5(Al,Si)8O22(OH)2. Plagioclase occurs as inclusions in both pyroxene and biotite. Biotite has high concentration of TiO2 and extremely low CaO. The opaque mineral observed is ilmenite and it is concentrated around hypersthene and amphibole. Rare earth element (REE) displays negative Eu anomaly with enrichment of light REE over heavy REE. Amphiboles surrounding orthopyroxene are evidences of retrograde reactions and are formed at the expense of orthopyroxene reacting with plagioclase and quartz in the presence of fluid. The relationship between the mineral assemblages suggests the retrogression of the gneiss that might be as a result of rehydration process, and it is a transition from granulite facies to amphibolite facies during a retrogressive form of metamorphism.
</abstract>

Department of Geosciences, Faculty of Science

Department of Geological Science, College of Science, Engineering and Technology

Earth, Environmental and Planetary Sciences

Retrogression of Orthopyroxene-bearing Gneiss of Iboropa Akoko, Southwestern Nigeria

<abstract xmlns="http://www.w3.org/1999/xhtml">

A high-resolution biostratigraphic study of the STEP-1 well, offshore Western Niger Delta Basin, Nigeria, was carried out using foraminifera, calcareous nannofossils and palynomorphs. The study was aimed at identifying the biostratigraphic zones, age deductions as well as palaeoenvironmental and palaeoclimatic reconstructions. From the studied well section of 609 m (1,829–2,438 m), 50 ditch cuttings were used for foraminifera and calcareous nannofossils, while 25 samples were used for palynological studies at 12 m and 24 m intervals, respectively. Standard laboratory preparation techniques were employed for the three microfossil groups. Due to the occurrence of some forms such as <italic>Globigerina praebulloides</italic>, <italic>Haplophragmoides spp, Bolivina scalprata miocenica, Valvulina flexilis and Cyclammina cf.</italic> minima, two planktonic and one benthonic foraminifera zones were identified as follows: Lower N18, Upper N17 zone (early Pliocene, late Pliocene) and <italic>Cyclammina minima</italic> zone (late Miocene), respectively. Two biozones were recognized for the nannofossils and include NN12 (<italic>Ceratolithus cristatus zone</italic>) and NN11 (<italic>Discoaster berggrenii</italic> zone). These zones were assigned to early Pliocene and late Miocene, respectively. Other forms include <italic>Discoaster pentaradiatus, Sphenolithus abies</italic> and <italic>Ceratolithus armatus. Echitricolporites spinosus</italic>/P800zone has been assigned for the Palynomorph assemblages and was dated late Miocene due to the quantitative occurrence of <italic>Cyperaceaepollis spp</italic>. Four identified major condensed sections include intervals at 1,926, 1,987, 2,097 and 2,316 m, which have been dated 5.0, 5.8, 6.3 and 7.0 Ma, respectively. Based on the benthonic foraminiferal species and Palynological Marine Index, a shallow marine environment is deduced for the studied interval which was interpreted to be deposited under both wet and dry palaeoclimatic conditions. The findings, no doubt could serve as a template for a sequence stratigraphic model, generally beyond the resolution of seismic stratigraphy.
</abstract>

High-resolution Biostratigraphic Studies of Step-1 Well, Offshore, Western Niger Delta

<abstract xmlns="http://www.w3.org/1999/xhtml">

The authors describe electrical resistivity method using a laboratory experiment, which was conducted in order to calculate the percentage of current that penetrated each layer of soil arranged in a container using Schlumberger array. Four soil samples arranged in three different set-ups were used. The apparent resistivity obtained was interpreted using curve matching techniques and WinResist iteration yielding types A curve, H curve and A curve, respectively. The interpreted data gave the resistivity of each layer and its thicknesses. The thicknesses obtained from the interpretation were at variance with the actual thicknesses arranged in the container. A multiplier was obtained which serves as a constant in other to obtain the actual thickness. The effective penetration depth of current was determined through the calculated thickness of each layer and the known electrode spacing (AB). The percentage of current that penetrates the layers was found to depend on the electrode spacing as well as the thickness of that layer. Thus, a layer with relatively small thickness has a small percentage of current passing through it compared to a thicker layer.
</abstract>

Fractional Current Flow in the Subsurface Using Electrical Resistivity Method: A Laboratory Approach

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Materials and Geoenvironment

 Description:  Old title: Rudarsko-metalurški zbornik (Mining and Metallurgy Quaterly).  Is issued quarterly by the Faculty of Natural Sciences and Engineering, Ljubljana, Velenje Coal Mine, Velenje, Institute for Mining, Geotechnology and Environment (IRGO), Ljubljana and Slovenian Chamber of Engineers, Ljubljana.  Financially supported also by Ministry of Higher Education, Science and Technology Republic of Slovenia.  Issues up to the volume 62 you can find on our old web page at address: www.rmz-mg.com/contents.htm  The journal does not have article processing charges (APCs) nor article submission charges.  Archiving  Sciendo archives the contents of this journal in Portico - digital long-term preservation service of scholarly books, journals and collections.  Plagiarism Policy  The editorial board is participating in a growing community of Similarity Check System's users in order to ensure that the content published is original and trustworthy. Similarity Check is a medium that allows for comprehensive manuscripts screening, aimed to eliminate plagiarism and provide a high standard and quality peer-review process. 