24 research outputs found
Electric and elastic properties of low-permeability sediments
No full textAs part of the 2020 North Sea Agreement, Denmark will decommission many hydrocarbon-producing wells, necessitating the evaluation of petrophysical and elastic properties of reservoir chalks and overburden diatomaceous shales to ensure safe operations. This PhD research refined geophysical logging interpretations by studying electrolytic conduction and elasticity of fine-grained sediments like chalks and diatomites.Given the high surface area of these fine-grained sediments, initial research focused on understanding electrolytic conduction in porous media by exploring the role of the electrical double layer. This study analyzed ionic adsorption dynamics of diatomite powders which complemented complex conductivity measurements on twenty-six saltwater-saturated diatomite and chalk samples. Results indicated a significant shift in current transmission from being predominately surface-water-dominated or slightly bulkwater-dominated, to being exclusively bulk-water-dominated with increasing NaCl concentration. At high salinity, bulk water governs conduction, raising Archie’s mexponent above 1.5 and enabling the calculation of the proportion of pore space occupied by bulk versus surface water. A model predicting sample conductivity as a function of bulk water conductivity was proposed and enabled the calculation of surface conductivity. Chargeability was found to gradually decrease with increasing salinity, reflecting the dominant role of bulk water in current transmission. Although the phase shift magnitude varied with pore water salinity, the distribution patterns remained consistent, reflecting the distinct mineralogical composition of each sample.Geomechanical uniaxial compaction tests on twelve chalk samples showed that transitions in mechanical behavior could be consistently described by strain under different saturation conditions: dry, isopar-L oil-saturated, and tap-water-saturated. During these tests, significant noise and misleading wave arrivals in the recorded S-wave trains complicated the detection of the actual S-wave arrival. To add confidence in the Swave arrival detection, a method was proposed combining graphical representations of stacked wave trains. The method produced results congruent with the iso-frame modeled P-wave, shear, and bulk moduli.The principles derived from studying the electric and elastic properties of diatomites and chalks were applied to improve well log interpretation in two Danish North Sea wells: the water-saturated diatomaceous shale in the Sten-1 well and the water-wet hydrocarbon-bearing clay-rich chalk reservoir in the Boje-2C well. The composition of formation solids was quantified using cuttings or core sample information, and porosity was assessed from neutron and density logs. Applying the new electrolytic conduction model, petrophysical properties such as surface area, permeability, irreducible water saturation, water saturation, and water salinity were acquired without using Archie's m- or n-exponents. Additionally, elastic moduli calculated by sonic and density logs were substituted to dry state allowing the calculation of Biot's coefficient and vertical elastic strain; the latter facilitated the identification of significant compaction in the Sten-1 well
Petrophysical characterization of Lower Cretaceous marly chalk through <sup>1</sup>H-NMR and complex conductivity
No full textComplex conductivity and T2 relaxation time spectra were acquired in ten marly chalk samples from Lower Cretaceous and one outcrop chalk sample from Upper Cretaceous. The results demonstrated that the quadrature conductivity spectrum provides information on pore space geometry similar to the T2 relaxation time domain. Sample conductivity was lower in samples showing higher quadrature conductivity at lower electromagnetic frequency. Deriving chargeability by a Cole-Cole model, we identified that chargeability increases with the increase of specific surface area of the total volume. This finding has implications for well-logging techniques that derive matrix permeability information using electrical conductivity measurements at distinct frequencies. In conclusion, this study highlights the potential of complex conductivity and chargeability measurements, along with applying Kozeny's equation, to provide valuable information on pore space characteristics and matrix permeability. This information can enhance our understanding of subsurface formations and aid in reservoir characterization and hydrocarbon exploration efforts
Are diatomites threatening the stability of closed wells?:The possibility of the Lark Formation transmitting hydrocarbons into penetrating wells
No full text
Parametric Analysis of Viscoelastic Hyperboloidal Helical Rod
No full textErmis, Merve/0000-0003-0201-6586; Kutlu, Akif/0000-0001-6865-3022; Eratlı, Nihal/0000-0003-3788-9870; OMURTAG, Mehmet Hakki/0000-0003-2669-6459The objective of this study is to perform a pioneering research about a viscoelastic hyperboloidal helical rod having a standard type of distortional behavior and a Kelvin type of bulk compressibility. Field equations are based on the Timoshenko beam theory, and the exact curvatures of the hyperboloidal geometry are considered through the formulation. The numerical analysis is carried out by the mixed finite element method, considering the rotary inertia, in the Laplace space, and the results are transformed back to time space numerically using the modified Durbin's algorithm. A cantilevered hyperboloidal helical rod having solid circular, hollow circular, and thin-walled hollow circular cross sections is handled, and the rod is loaded by rectangular and triangular impulsive types of point load at the tip. Through the analysis, different values of retardation time, three different relaxation functions associated with shear modulus, and three different creep functions associated with bulk modulus are handled. Finally, a benchmark example is presented, and the influence of the loading and the material parameters on the helix geometry is discussed.Scientific and Technological Research Council of Turkey [111M308]; Research Foundation of ITU [38078]The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research is supported by the Scientific and Technological Research Council of Turkey under project no. 111M308 and Research Foundation of ITU under project no. 38078
Επίδραση της αλατότητας επί της διαλυτότητας αερίων σχηματισμού υδρίτη σε υγρά μείγματα νερού-υδρογονανθράκων
No full textΠερίληψη: Οι υδρίτες αερίων βρίσκονται στο επίκεντρο πολλών μελετών κατά τα τελευταία
χρόνια. Οι οικονομικές ζημίες που προκαλούνται κατά τη δημιουργία τους σε αγωγούς
μεταφοράς αερίων, τους μετατρέπουν σε εχθρό της βιομηχανίας του πετρελαίου. Επιπλέον,
η μαζική αποδόμησή τους κρύβει κίνδυνο όσον αφορά τις περιβαλλοντικές επιπτώσεις που
επιφέρουν, καθώς το μεθάνιο, που είναι το κύριο αέριο συστατικό που εγκλωβίζεται σε
αυτούς, είναι αέριο που ευθύνεται για τις κλιματικές αλλαγές. Από την άλλη, υπολογίζεται
ότι η ποσότητα ενέργειας που είναι αποθηκευμένη σε αυτούς είναι διπλάσια αυτής που
περιέχεται στα ορυκτά καύσιμα της Γης. Σύγχρονοι οικονομικοί μέθοδοι εξόρυξης
βρίσκονται υπό έρευνα και πολλές μελέτες κατευθύνονται στην κατανόηση του μηχανισμού
λειτουργίας τους. Η κλασική πειραματική μεθοδολογία που έχει αναπτυχθεί ως προς την
κατανόηση της συμπεριφοράς των υδριτών, προέρχεται από τη διαδικασία του
προσδιορισμού της διαλυτότητας των αερίων στην υδατική φάση κατά τη διφασική ή
τριφασική ισορροπία.
Σε αυτή την εργασία, αναφέρονται πειραματικές μετρήσεις των διαλυτοτήτων του
μεθανίου στην υδατική φάση κατά την ισορροπία μεθανίου - υδατικής φάσης - υδρίτη
καθώς και ενός μείγματος αερίων (80% μεθάνιο, 5% αιθάνιο, 5% προπάνιο, 5% άζωτο, 5%
διοξείδιο του άνθρακα) κατά την ισορροπία νερού/αλατόνερου με υδρίτη σε χαμηλές
θερμοκρασίες. Χρησιμοποιήθηκαν δύο κυλινδρικά εμβολοφόρα κελιά, εκ των ποίων το ένα
για την υδατική φάση και το δεύτερο για την αέρια φάση όγκων 1000ml και 500ml,
αντίστοιχα. Εμβολοφόρα αντλία ISCO χρησιμοποιήθηκε ώστε να κατευθύνει τα ρευστά
προς τον αυτόκλειστο αντιδραστήρα τύπου Parr, ο οποίος διέθετε εσωτερικό όγκο 100ml.
Το αυτόκλειστο βυθίστηκε σε υδατόλουτρο ώστε να διατηρεί τη θερμοκρασία σταθερή.
Εντός του αντιδραστήρα υπήρχαν μανόμετρο, θερμόμετρο και μαγνητικός αναδευτήρας.
Μεθάνιο και απιονισμένο νερό σχημάτισαν υδρίτη και τα δεδομένα θερμοκρασιών –
πιέσεων ισορροπίας συγκεντρώθηκαν σε ηλεκτρονικό υπολογιστή με λογισμικό LabVIEW.
Χρησιμοποιήθηκε σύριγγα για τη δειγματοληψία διαλυτοτήτων μεθανίου, με μέθοδο
εκτόνωσης σε ισορροπία συστήματος υδρίτη – υδατικής φάσης σε εύρος θερμοκρασίας και
πίεσης από 278-291 Κ και από 3,8 MPa έως 20 MPa αντίστοιχα. Τα αποτελέσματα
συγκρίθηκαν με τη βιβλιογραφία και συμπίπτουν ικανοποιητικά. Το αέριο μείγμα
δοκιμάστηκε για αλατότητες 0% (απιονισμένο νερό), 3% και 8%. Τα ρευστά παρέμειναν
εντός του αυτοκλείστου με συνεχή ανάδευση για 72 ώρες, ώστε να επιτευχθεί ισορροπία
νερού/ αλατόνερου - υδρίτη. Μετρήσεις διαλυτότητας του μείγματος αερίου στην υδατική
φάση διεξήχθησαν σε θερμοκρασιακό εύρος 278-288 Κ και σταθερή πίεση 16,9 MPa. Όταν
συλλέχθηκαν τα δείγματα, η σύριγγα παρέμεινε σφραγισμένη για 24 ώρες ώστε να
απελευθερωθεί πλήρως το διαλελυμένο αέριο. Τέλος, η σύριγγα κατευθύνθηκε σε αέριο
χρωματογράφο τύπου PERKIN ELMER 8700 για χρωματογραφική ανάλυση ώστε να
εντοπιστούν οι διαλυτότητες των επιμέρους συστατικών του αερίου μείγματος. Τα
αποτελέσματα των μετρήσεων από τα πειράματα με τους διάφορους βαθμούς αλατότητας
συγκρίθηκαν μεταξύ τους και επιβεβαίωσαν ότι η αλατότητα μειώνει τη διαλυτότητα του αερίου μείγματος στην υδατική φάση ως κάποιο βαθμό ενώ περαιτέρω αύξηση της
αλατότητας επιφέρει αμελητέες αλλαγές στη διαλυτότητα των αερίων στην υδατική φάση
Multi-agent Planning and Coordination for Automated Aircraft Ground Handling
No full textInspired by the vision of fully autonomous airside operations at Schiphol airport, this study aims to contribute to the short-term goal of automated aircraft ground handling. In this research, we design and evaluate a multi-agent system for planning of automated ground handling. There are two main components in the system, task allocation optimization, and multi-agent path planning. To allocate tasks to ground support equipment (GSE) vehicles, an auction mechanism inspired by temporal sequential single item (TeSSI) auction is proposed. Ground handling tasks scheduling for GSE vehicles is modeled as several single-vehicle pickup and delivery optimization problems (SPDP), and the values of the objective functions are applied to generate bids for GSE vehicle agents in the auction. Moreover, Prioritized Safe Interval Path Planning for large agents (LA-SIPP) is used to plan collision-free paths for GSE vehicle agents in the model to execute tasks. Experimental studies have shown that the system is able to perform task allocation and path planning of ground handling tasks for flights in 3 aircraft stands within a 4-hour time in a reasonable computational time. Moreover, the model is capable to replan the tasks for agents when disruption happens. Applying the lowest possible numbers of vehicles used in the current operation, the model can always reach success allocation and path planning rates higher than 81% and 98%, respectively.Aerospace Engineerin
Multi-agent planning and coordination for automated aircraft ground handling
No full textInspired by the vision of fully autonomous airside operations at Schiphol airport, this study aims to contribute to the short-term goal of automated aircraft ground handling. In this research, we design and evaluate a multi-agent system for planning of automated ground handling. There are two main components in the system: task allocation optimization and multi-agent path planning. To allocate tasks to ground support equipment (GSE) vehicles, an auction mechanism inspired by temporal sequential single item (TeSSI) auction is proposed. Ground handling tasks scheduling for GSE vehicles is modeled as several single-vehicle pickup and delivery optimization problems (SPDP), and the values of the objective functions are used to generate bids for GSE vehicle agents in the auction. Prioritized safe interval path planning for large agents (LA-SIPP) is used to plan collision-free paths for GSE vehicle agents in the model to execute tasks. The aim is to increase the success rates of allocating tasks and finding collision free paths without causing flight delays, given the limited resources such as a small number of available GSE vehicles, time windows constraints and conflicting interests of different agents. Due to the results, even for the instances with frequent flights and the most limited resources, the success rates of allocation and path planning were higher than 81% and 98%, respectively. Furthermore, periodic task allocation and path planning of the ground handling tasks for flights in three aircraft stands during a planning time window of the day, as well as replanning in case of disruptions were performed in a short CPU time. There is a lack of research dealing with the complete process of ground handling, since existing studies concerning the automation of ground handling operations involve fleet assignment or task scheduling models without an integration of detailed path planning. Our main contribution is to present a framework that combines task allocation and path planning for automation of ground handling operations and provides solutions using a multi-agent perspective.Air Transport & Operation
The Calculation of Mass Attenuation Coefficients of Well-Known Thermoluminescent Dosimetric Compounds at Wide Energy Range
No full text32nd International Physics Congress of Turkish-Physical-Society (TPS) -- SEP 06-09, 2016 -- Bodrum, TURKEYThe photon mass attenuation coefficients of LC BaSO3, CaCO3 and CaSOzi thermoluminescent dosimetric compounds at 100; 300; 500; 600; 800; 1,000; 1,500; 2,000; 3,000 and 5,000 keV gamma-ray energies were calculated. For this purpose, FLUKA Monte Carlo (MC) program which is one of the well-known MC codes was used in this study. Furthermore, obtained results were analyzed by means of ROOT program. National Institute of Standards and Technology (NIST) values were also used to compare the obtained theoretical values because the mass attenuation values of the used compounds could not found in the literature. Calculated mass attenuation coefficients were highly in accordance with the NIST values. As a consequence, FLUKA was successful in calculating the mass attenuation coefficients of the most used thennoluminescent compound.Turkish Phys SocEge UniversityEge University [2014 FEN 026]The Author thanks to Dr. E. Pilicer for his help in the calculation procedure and to Dr. C. Celiktas for his precious contribution to the study. This work was supported by Scientific Research Project of Ege University under Project No. 2014 FEN 026
