ODABIR DLIJETA ZA BUŠENJE STIJENA S RAZLIČITIM TALOŽNIM FACIJESIMA UPORABOM METODE MARKOVLJEVA LANCA: PRIMJER STUDIJE NAFTNOGA POLJA U JUŽNOME IRANU

The selection of a drill bit is an essential issue in well planning. Furthermore, identification and evaluation of sedimentary rocks before well drilling plays a crucial role in choosing the drill bit. Moreover, the Markov chain as a stochastic model is one of the powerful methods for identifying lithological units, which is based on the calculation of the transition probability matrix or transition matrix. The Markov chain experiences transitions from one state (a situation or set of values) to another according to specified probabilistic rules. In this paper, the Markov chain was implemented for bit selection in a formation with different sedimentary facies (such as the Dashtak Formation). Therefore, the proper drill bit was proposed by utilizing the transition matrix of rock facies and the available bits. This process was carried out in two wells where the thicknesses of the Dashtak Formation are 960 meters and 1410 meters. Consequently, the results indicate that the Markov chain is a practical method for selecting bits in a sequence of rock facies based on an acceptable matching between the reality mode (the used bits in the well) and the Markov chain results. Besides, in the case of using an improper bit in a well, and using a bit in a washing and reaming operation, there were differences between the used bits and the Markov chain outputs.Odabir dlijeta iznimno je važan korak u izradi projekta bušotine, a prepoznavanje i procjena taložnih stijena prije početka bušenja ima presudnu ulogu u odabiru dlijeta. Markovljev lanac, kao primjer stohastičkoga modela, jedna je od važnijih metoda za razlikovanje litoloških jedinica. Temelji se na računu matrice vjerojatnosti prijelaza ili matrice prijelaza. Markovljev lanac opisuje prijelaze iz jednoga stanja (situacije ili skupa vrijednosti) u drugo prema određenim vjerojatnosnim pravilima. U ovome je radu prvi put opisana uporaba Markovljeva lanca kod odabira dlijeta za bušenje kroz interval s različitim taložnim facijesima (formacija Dashtak). Stoga su u odabiru odgovarajućega dlijeta korišteni prijelazna matrica stijenskih facijesa i podatci o dostupnim dlijetima. Ovaj postupak proveden je u dvjema bušotinama gdje su debljine formacije Dashtak 960 i 1410 m. Dobiveni rezultati pokazuju da je Markovovljev lanac praktična metoda za odabir dlijeta kod bušenja niza litofacijesa. Zaključak je donesen na temelju stupnja podudaranja između stvarnih podataka (dlijeta korištenih u bušotini) i rezultata dobivenih modelom (Markovljevim lancem). Također, u slučaju uporabe neodgovarajućega dlijeta u bušotini za operacije pročišćavanja i proširenja kanala bušotine pojavile su se razlike između korištenih dlijeta i rezultata dobivenih Markovljevim lancem

Assessing Hydrothermal Conditions At Lassen Volcano With Implications For Early Mars

Hydrothermal sites explored at Lassen Volcano, California reveal alteration processes ranging from acid-sulfate to more neutral conditions that can be either oxidizing or reducing. Often, these different environments arise near each other and are therefore closely linked. In this report, X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) analysis of minerals combined with water data collected in-situ will be interpreted to reveal alteration pathways as dacitic to andesitic host rocks come into contact with these hydrothermal conditions. Fumaroles at Pilot\u27s Pinnacle and Terminal Geyser eject plumes of volatiles that yield acidic condensates, leading to leaching of most soluble ions and, in some cases, S precipitation. Pilot\u27s Pinnacle also hosts a cool, near-neutral stream actively precipitating minerals. Together these observations allow us to understand fine-scale behavior in a complex alteration system.Acid-sulfate and near-neutral hydrothermal environments have beeninvoked to explain certain geological features on Mars such as silica enrichment and sulfate minerals inrocks and soils. These environments have been observed by Mars Exploration Rover (MER) Spirit atHome Plate, Gusev crater. Furthermore, evidence of more evolved (dacitic/andesitic) volcanism has also been provided by Mars Science Lab (MSL) Curiosity. On Earth, hydrothermal environments sustain diverse microbial ecosystems. Better understanding chemical behavior in terrestrial systems can allow us to apply more refined interpretations to observations gathered in the search for biosignatures on Mars, and help to identify noteworthy samples for collection in future missions to Mars

Use of natural ores as oxygen carriers in chemical looping combustion: A review

Chemical looping combustion (CLC) has gained considerable ground in energy production due to its inherent carbon capture with a minimal energy penalty. The choice of metal oxide used as an oxygen carrier (OC) in CLC has a substantial weight on the overall efficiency of energy production as well as the ultimate cost per MW. While much work has gone into manufacturing synthetic OCs with high fuel conversions, harsh operating conditions and process limitations cause some unavoidable loss of the oxygen carrier. With low production costs and minimal conditioning required, natural ores have grown in interest as cheap alternative oxygen carriers. This work provides a substantial literature review of recent works studying the use of natural ores in CLC. Iron-based, manganese-based, copper-based and calcium based ores were found to be the main ores researched, along with mixtures of these ores and natural ores with minor additional compounds. Typical parameters have been collected for each study including; fuel conversion, stability, physical characteristics, and carbon capture efficiency. Natural ores are compared with purified metal oxides to highlight strengths and weaknesses of each ore and recommendations for future studies are made

Passive control of a falling sphere by elliptic-shaped appendages

The majority of investigations characterizing the motion of single or multiple particles in fluid flows consider canonical body shapes, such as spheres, cylinders, discs, etc. However, protrusions on bodies -- being either as surface imperfections or appendages that serve a function -- are ubiquitous in both nature and applications. In this work, we characterize how the dynamics of a sphere with an axis-symmetric wake is modified in the presence of thin three-dimensional elliptic-shaped protrusions. By investigating a wide range of three-dimensional appendages with different aspect ratios and lengths, we clearly show that the sphere with an appendage may robustly undergo an inverted-pendulum-like (IPL) instability. This means that the position of the appendage placed behind the sphere and aligned with the free-stream direction is unstable, in a similar way that an inverted pendulum is unstable under gravity. Due to this instability, non-trivial forces are generated on the body, leading to turn and drift, if the body is free to fall under gravity. Moreover, we identify the aspect ratio and length of the appendage that induces the largest side force on the sphere, and therefore also the largest drift for a freely falling body. Finally, we explain the physical mechanisms behind these observations in the context of the IPL instability, i.e., the balance between surface area of the appendage exposed to reversed flow in the wake and the surface area of the appendage exposed to fast free-stream flow.Comment: 16 pages, 13 figures, 2 tables, under consideration for publication in Phys. Rev. Fluids; revisio