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Diploma Thesis Project Summarization: The current diploma thesis project focuses in utilizing the ECLIPSE reservoir simulation software to optimize the well placement processes in a given reservoir and the history matching processes of the simulation model data with the history data that accompany the simulation model. The optimization processes mentioned above will be conducted on the simulation model built for a block that is part of Gullfaks reservoir in the North Sea, Norway. PlanOpt and SimOpt are modules of ECLIPSE reservoir simulation software, PlanOpt is used to optimize the well placement processes and SimOpt is used to optimize the history matching processes of the simulation model data with the history data that accompany the simulation model. As far as well placement optimization is concerned, the already existing production wells of the simulation model will be discarded and by utilizing the well placement optimization software, PlanOpt, a less or equal number of production wells will be placed on the simulation model and will be scheduled to operate for the same simulation period that the initial simulation model is operating, aiming finally to achieve equal or higher cumulative oil production than the initial simulation model at the end of the simulation period. SimOpt will be used to reduce the mismatch between the production data of the simulation model and the real production data that were reported during the operation of the wells on the field. Several reservoir parameters will be set to vary within a range and at the end of the optimization processes SimOpt will calculate the values of the parameters chosen which produce the least possible mismatch between the real production data and the data resulted from the simulation model. Since there are different types production data that are going to be matched, a study will be conducted of whether the type of production data which are going to be matched in each different simulation run of SimOpt, affect the resulted matching at the end of each optimization run.

Summarization: Objective of the study is to implement the commercially available software tools to the basic reservoir engineering problems in a real field case. Eclipse data set of Norne field, in the Norwegian sea, has been used for the study that is publicly available on https://opm-project.org/?page_id=559. Eclipse 100 and tNavigator have been used to run the simulations for verifying the feasibility of application of the ASP flooding for improving recovery. Norne benchmark case is a real field black-oil model for an oil field in the Norwegian Sea. The model included dissolved gas, vaporized oil, transmissibility multipliers, pressure-dependent porosity and transmissibility, end-point scaling for relative permeability and capillary pressure. History-matching of production and pressures has already been done and well controls that change throughout the simulation schedule have also been included in the model. Application of ASP flooding technique has been simulated in E100 and tNavigator as part of the study purpose. As matched in the history, water injection starts very early in the field. There are total 36 wells of which 9 are injection wells and the remaining 27 are production wells. Five wells are exclusively water injection wells and they have been used to inject ASP slugs along with the water. In Eclipse E100, alkaline model is a simple model that does not take any chemical reactions into consideration, but when used in conjunction with surfactant and polymer to perform an Alkaline-Surfactant- Polymer (ASP) flooding, the alkaline can reduce the adsorption of both surfactant and polymer on the rock surface, therefore enhancing the effectiveness of the surfactant and polymer drive. Eclipse and tNavigator work in the same format of E100 text pad code. Results from the both software are comparable. tNavigator has a very good graphical user interface to interact with the tool and all the graphs are defaulted and simultaneously can be viewed as the simulation time progress and it is faster than the Eclipse 100.

Summarization: It is widely accepted among the petroleum engineering community that Enhanced Oil Recovery (EOR) is currently one of the most active sectors of research in the oil industry. The first part of the present diploma thesis consists of a literature review where the commercially feasible Enhanced Oil Recovery methods are described. The oil recovery mechanisms each EOR method involves, the advantages, the disadvantages and some examples of successful field applications are presented. At the end of the literature review, the reader will have a good perception of the necessity of EOR implementation in the existing oil fields, the production potential of the EOR techniques and the ability to identify where and at which extent each EOR method can be applied. The second part of the present diploma thesis investigates the implementation of Chemical EOR methods in the H1 segment of the offshore oil field named Gullfaks that is found in the Norwegian side of the North Sea. At first, a presentation of the reservoir properties is made and then a simulation study of the reservoir is conducted using ECLIPSE - 100 (2010 version) software.

Περίληψη: Ο σκοπός της διπλωματικής εργασίας είναι η υπολογιστική μελέτη των συνθηκών ροής κατά τη διεργασία εισαγωγής νερού (waterflooding) σε ετερογενείς και ανισότροπους ταμιευτήρες πετρελαίου με χρήση του υπολογιστικού λογισμικού COMSOL Multiphysics. Για τις προσομοιώσεις ροής έγινε χρήση του module του COMSOL για πολυφασική ροή σε πορώδες μέσο. Η εργασία χωρίζεται σε τρία βασικά υπολογιστικά μέρη. Στο πρώτο μελετάται η πιο απλή εκδοχή του προβλήματος η οποία είναι η δευτερογενής παραγωγή σε έναν τυπικό ομοιογενή και ανισότροπο σχηματισμό. Στο δεύτερο μέρος ο σχηματισμός παρουσιάζει διαστωμάτωση και ετερογένεια. Τέλος, επιλύεται ένα αρκετά συνθετότερο πρόβλημα όπου η εκμετάλλευση του ταμιευτήρα γίνεται από τέσσερα φρεάτια παραγωγής και οκτώ εισαγωγής νερού, καθώς και πιο σύνθετη γεωμετρία. Το συγκεκριμένο μοντέλο ονομάζεται Εgg Model και αποτελεί ένα σύγχρονο σενάριο αναφοράς της SPE για τη σύγκριση υπολογιστικών εργαλείων πολυφασικής ροής. Εκτός από την ψηφιακή απεικόνιση κάθε περίπτωσης από το υπολογιστικό πρόγραμμα δημιουργήθηκαν και όλα τα κατάλληλα διαγράμματα για την αξιολόγηση του κάθε σεναρίου παραγωγής, όπως επίσης και τα συγκριτικά διαγράμματα τα οποία είναι απαραίτητα για την κατανόηση της δυναμικής συμπεριφοράς του κάθε κοιτάσματος. Τα αποτελέσματα τα οποία παρουσιάζονται επιβεβαιώνουν ότι το συγκεκριμένο module του COMSOL Multiphysics για πολυφασική ροή σε πορώδες μέσω είναι ένα αξιόπιστο εργαλείο για την επίλυση αρκετά σύνθετων προβλημάτων της μηχανικής εκμετάλλευσης ταμιευτήρων.

Summarization: Tracer techniques are a powerful diagnostic tool in numerous Scientific disciplines (Bjornstad et al.,1990; Divine and McDonnell, 2005) and for technologies in many industrial sectors. Tracer tests were first used in the early 1900s in hydrology (Du and Guan, 2005; Guan etal.,2005). Today, these tests are used with increasing frequency in oil field applications (Bingyu et al.,2002; Bjornstad, 1991; Jin et al.,1997) when no other investigation technique is applicable. Tracer tests provide a better understanding of the studied oil reservoir (including inter well connections, connections between layers and heterogeneities) (Coronado and Ramirez-Sabag, 2008; Coronado et al., 2009; Guan and Du, 2004; Manich and et al., 2010; Nugroho and Ardianto, 2010; Sinha e tal., 2004). The Single-well Tracer Test is a test used extensively to measure the S_or (Residual oil) in watered-out reservoirs. Also, it is implemented in order to evaluate enhanced oil recovery (EOR) using chemicals, such as Alkaline/Surfactant/Polymer flooding. Single-Well Chemical Tracer (SWTT) tests offer an in-situ method for determining the Residual Oil Saturation (R_OS) of a reservoir that has numerous advantages, compared to more conventional methods such as core analysis and well logging. It can also be used to enhance the understanding of heterogeneity in the subsurface. Over the past 50 years numerous SWCT and IWCT (Inter-Well Chemical Tracer) tests have been conducted in fields around the world. Most of these tests focused on measuring the R_OS as an aid to planning improved oil recovery processes, and to understand the results of these tests. In this work, tracer responses to two different commercial simulators (C.M.G. Stars and Eclipse Schlumberger) are analysed using numerical modelling. Two methods are applied: use of a multi-component reservoir simulation model, with chemical reactions to represent the reactive hydrolysis behaviour of the tracer (C.M.G. Stars); and a simplified approach using tracer tracking in a conventional black oil simulation model (Eclipse, Schlumberger). The models’ results are validated against field data and it is shown that the simulation results are consistent when varying grid thickness and keeping other parameters unchanged. When different rock and fluid properties are introduced, numerous peaks are observed, illustrating delays in tracer arrival times due to flow irreversibility. The reservoir simulation models can be used for forward modelling and sensitivity studies to design SWTT tests, and for interpreting saturation measurements obtained in such tests. They can also be used for other applications, in conjunction with other data sources such as well logs.

Μη διαθέσιμη περίληψη Not available summarization

Περίληψη: Στην παρούσα εργασία προσδιορίστηκαν πειραματικά οι συντελεστές κατανομής τριών ελαφριών αλκοολών (μεθανόλη, αιθανόλη, 2-προπανόλη) σε δυαδικά συστήματα αποτελούμενα από μια υδατική φάση και μια ελαϊκή φάση. Ως ελαϊκή φάση χρησιμοποιήθηκαν οι παρακάτω διαλύτες: εξάνιο, επτάνιο, τολουόλιο, ξυλόλιο και τετραχλωράνθρακας. Η επιλογή των διαλυτών έγινε για την προσομοίωση της συμπεριφοράς των αλκοολών, των πολικών φάσεων και των χαρακτηριστικών των μη-υδατικών φάσεων που απαντώνται στο υπέδαφος (Non-aqueous phase liquids, NAPL) κατά τις διαρροές οργανικών μιγμάτων ή πετρελαίου. Η γνώση των συντελεστών κατανομής είναι σημαντική για την προσομοίωση των διαρροών οργανικών ρύπων στο περιβάλλον. Επίσης, συστατικά όπως οι αλκοόλες που μελετήθηκαν, χρησιμοποιούνται σε μελέτες υπολογισμού του υπολειμματικού βαθμού συγκέντρωσης νερού ή πετρελαίου σε ταμιευτήρες υδρογονανθράκων, όπως οι δοκιμές μονού ή διπλού φρέατος (Single Well Tracer Test, SWTT ή Double Well Tracer Test, DWTT). Ο προσδιορισμός των συντελεστών κατανομής των αλκοολών έγινε μέσω του υπολογισμού της συγκέντρωσής τους στην υδατική φάση. Για τον προσδιορισμό των συγκεντρώσεων αυτών, χρησιμοποιήθηκε η τεχνική της αέριας χρωματογραφίας με ανιχνευτή ιονισμού φλόγας (Flame Ionization Detector, FID) με τρείς διαφορετικές μεθοδολογίες εισαγωγής του δείγματος. Την απευθείας εισαγωγή της υδατικής φάσης (direct injection), την εισαγωγή δείγματος υπερκείμενης φάσης αερίου (Headspace sampling) και την μικροεκχύλιση στερεής φάσης (Solid Phase Microextraction, SPME). Με βάση τα πειραματικά αποτελέσματα, η τεχνική Headspace αποδείχτηκε ότι οδηγεί σε χαμηλότερα όρια ανίχνευσης και ποσοτικού προσδιορισμού των τριών αλκοολών στο νερό. Οι τιμές των συντελεστών κατανομής που προσδιορίστηκαν για τις αλκοόλες στα δυαδικά συστήματα υδατικής-ελαϊκής φάσης βρέθηκαν σε συμφωνία με αντίστοιχα βιβλιογραφικά δεδομένα. Summarization: In this study, partition coefficients of three light alcohols (methanol, ethanol, 2- propanol) were experimentally determined in binary systems consisting of an aqueous phase and an oil phase. The oil phase was hexane, heptane, toluene, xylene and carbon tetrachloride. These solvents were used to simulate the behavior of alcohols, polar phases and non-aqueous phase liquids (NAPL) during leakage of organic mixtures or oil. The knowledge of the partition coefficient is important to simulate the leakage of organic pollutants into environment. Also, components such as these alcohols are used in studies to calculate the residual concentration of water or oil in hydrocarbon reservoirs, such as Single Well Tracer Test (SWTT) or Double Well Tracer Test (DWTT). The determination of partition coefficients of alcohols was made by calculating their concentration in the aqueous phase. For the determination of these concentrations, gas chromatography was used (with a flame ionization detector (FID)) with three different sample injection methods. Direct injection, Headspace sampling and Solid Phase Microextraction (SPME). Based on the experimental results, Headspace sampling has been shown to result in lower detection and quantification limits of the three alcohols in water. The values of the partition coefficients for the alcohols in the aqueous-oil phase systems were found in agreement with corresponding bibliographic data.

Summarization: The use of Partitioning Interwell Tracer Test is examined in the current thesis through the scope of black oil and chemical simulators (ECLIPSE and UTCHEM). Tracer tests have been thoroughly applied over the past decades as a means of reservoir characterisation. Partitioning Interwell Tracer Test is considered as a useful method for estimating oil volume and oil saturation, particularly before the application of Enhanced Oil Recovery methods, where the remaining oil saturation is close at its residual value. The accuracy of such predictions is investigated through the usage of ECLIPSE and UTCHEM simulators. Also, a sensitivity analysis to oil saturation distribution is conducted with regards residual oil saturation estimations. As chemical compounds, it is important to determine whether tracers’ transportation in the porous medium is sufficiently described through the equations that are provided in the aforementioned simulators. The latter are not meant to fully encapsulate all the probable mechanisms and reactions that may occur as tracers are injected into the reservoir and flow across the rock material. Numerical methods are also examined in the case of reservoirs that oil exhibits a non-residual saturation value. Furthermore, the use of partitioning tracers is investigated in heterogeneous reservoirs as well as in naturally fractured reservoirs as a qualitative means that may lead to useful information about flow patterns that cannot be easily deduced solely from production data themselves. Περίληψη: Στην παρούσα διπλωματική εργασία εξετάζεται η χρήση ιχνηθετών σε ταμιευτήρες πετρελαίου, υπό το πρίσμα προγραμμάτων προσομοίωσης της ροής εντός του ταμιευτήρα. Ιχνηθέτες έχουν χρησιμοποιηθεί ευρέως στην πετρελαϊκή βιομηχανία εδώ και πολλές δεκαετίες, ως μέσα ταυτοποίησης και χαρακτηρισμού της ροής των υδρογονανθράκων. Υδατόφιλοι ιχνηθέτες καθώς και ιχνηθέτες που διαχωρίζονται μεταξύ πετρελαϊκής και υδάτινης φάσης εγχέονται στον ταμιευτήρα. Διαφορές στο χρόνο κατά τον οποίο οι δυο τελευταίοι εξέρχονται της παραγωγικής γεώτρησης, δίνουν κρίσιμες πληροφορίες όσον αφορά συγκεκριμένα φαινόμενα ή μοτίβα ροής, καθώς και πληροφορίες για τους όγκους των ρευστών, τα οποία απαντούν στον ταμιευτήρα. Προκειμένου η εκτίμηση όσον αφορά τους όγκους των ρευστών να είναι επαρκής, απαιτείται η πετρελαϊκή φάση να βρίσκεται σε κατάσταση υπολειμματικού κορεσμού. Για το λόγο αυτό, η χρήση ιχνηθετών πραγματοποιείται ως επί το πλείστων προ της εκπόνησης Υποβοηθούμενης Ανάκτησης Πετρελαίου, η οποία αποτελεί τριτογενή μέθοδο παραγωγής. Αρχικά, είναι σημαντικό να καθοριστεί αν ροή των ιχνηθετών ως χημικά συστατικά απεικονίζεται επαρκώς μέσω της χρήσης προσομοιωτών ροής. Οι τελευταίοι βασίζονται στην εκπόνηση αριθμητικών προσεγγίσεων και εξ ορισμού δεν απαιτείται από αυτούς να αποδώσουν πλήρως τις αντιδράσεις, χημικές ή μη, οι οποίες λαμβάνουν χώρα εντός του ταμιευτήρα. Η χρήση των ιχνηθετών εξετάστηκε παράλληλα και σε ταμιευτήρες όπου ο κορεσμός στην πετρελαϊκή φάση ήταν μεγαλύτερος της υπολειμματικής τιμής. Επιπλέον, χρησιμοποιήθηκαν σε περιπτώσεις ετερογενών ταμιευτήρων, όσον αφορά τη διαπερατότητα καθώς και σε ταμιευτήρες οι οποίοι έχουν υποστεί φυσική ρωγμάτωση, κυρίως στην ποιοτική ανάλυση αυτών παρά την ποσοτική.

Μεταπτυχιακή Διατριβή στα πλαίσια του ΜΠΣ 'Pertoleum Engineering' Summarization: In the present thesis, a new dynamic model of H1 segment in the Gullfaks field, Norway, is built based on an updated static model. The update of the static model refers to the re-interpretation of a more recent seismic dataset, which resulted into a new structural model. The new static model was the basis for constructing a new grid for dynamic modelling for history matching. Two different datasets were combined for this purpose. The first dataset was an already existing dynamic model for H1 segment (Lower Brent Group) and production data, while the second one was a 3D seismic dataset along with a static model of the overlying Upper Brent Group for the entire Gullfaks field (Petrel support dataset). The predictions of the new dynamic model were different compared to those of the initial dynamic model, which most probably reflects the impact of the updated structure. However, based on the interpretation of the available seismic data it is considered that the updated structure is more consistent to geological setting of the area that the seismic reveal. Thus, by having a more representative geological static model and the production data history matched on the new grid, we can conclude that the updated dynamic model can predict the future performance of the studied reservoir with more confidence.

Summarization: The current thesis focuses on the numerical modeling of pore-to-field scale couplings in hydrodynamic dispersion and immiscible flows in porous media using the standard finite element framework provided by the commercially available software COMSOL Multiphysics. The single-phase flow is handled through the study of hydrodynamic dispersion during an ideal tracer injection by using COMSOL’s readily available Physics interfaces. The coefficient of hydrodynamic dispersion is explicitly calculated through rigorous pore-scale simulations in 2D porous domains and from the results obtained, a homogeneous model for porous media is defined using the calculated effective transport properties. The upscaling from the pore-scale to the REV-scale as far as transport properties of the porous medium are concerned is evaluated through the hydrodynamic dispersion coefficient and an appropriate volume-averaged expression of the mass conservation equation. Results indicated that statistical properties conveniently derived at the REV-scale, can successfully be used for the precise calculation of pore-scale transport properties. The two-phase incompressible flow during a waterflooding oil recovery process in a stratified petroleum reservoir is simulated via two numerical models; one that includes the gravitational terms and one that omits them. The equations of the mathematical flow model are derived under specific assumptions and formulated according to the fractional flow approach. The PDE modes in the general and coefficient form for time dependent analysis are utilized for their numerical implementation in COMSOL Multiphysics. An appropriate, numerically stable, formulation of the black oil model is then used for the simulation of two-phase compressible flow during a waterflooding process in an undersaturated petroleum reservoir. The model is based on the oil phase pressure and total velocity formulation. Its implementation in COMSOL is made with the time-dependent PDE interfaces. The physical models of the waterflooding processes are also implemented in ECLIPSE 100 simulator and the results from the two simulators are compared so as to evaluate the performance of the newly-developed COMSOL PDE modules in quantifying and interpreting relevant physical phenomena. The results from the incompressible fluid flow modeling revealed that both COMSOL models are generally in good agreement with ECLIPSE 100 as far as recovery is concerned, with the COMSOL model that neglects the gravity exhibiting a better matching. The results obtained from the implemented formulation of the black oil model are also very close to the ones from ECLIPSE 100 regarding hydrocarbons production rates. That indicates that COMSOL Multiphysics can efficiently be used as a trustworthy tool in hydrocarbons recovery predictions and also for the solution of more complex physics phenomena in reservoir simulation problems.

Summarization: Since the world is in constant need of energy sources and even if the renewable source energy plays and will play a key role in the increasing energy demands, the world will continue to be insufficient in sustainable energy. Thus unconventional reservoirs (tight/shale gas, tight oil, oil sands) will play an important part in satisfying the ever-increasing future energy demands, a fact that has drawn the attention of the petroleum industry. The declining oil and gas supply from conventional reservoirs combined with the drastic increase in unconventional oil and gas contribution has led us to the conclusion that unconventionals will hold a leading role in the global energy mix in the future. The difficult part is estimating the reserves and predicting future oil or gas well production of these types of reservoirs. An easy and relatively quick way of evaluating a well performance based on past production history data is the decline curve analysis. But when it is implemented in tight or shale reservoirs, the outcome might be unacceptable and unsatisfying probably due probably to ultra-low permeabilities and heterogeneities of the reservoir. All of the aforementioned led to the development of this thesis. In the first part some of the basic features of gas and oil shales and tight-gas sands reservoirs are presented, simultaneously with the assertive recovery solutions. Then a Capacitance-Resistance Model is used that was proposed firstly by Shahamat (2014) in order to show the equivalence between electrical and petroleum engineering. The continuous succession of pseudo-steady states is introduced to entitle the application of depletion equations through a step-by-step process to analyze the behavior of the reservoir during transient and boundary dominated flow. In the second part, the produced CRM model is compared with an analytical solution in order to verify the results and examine the reliability of the model which was proposed, for forecasting production rates during transient flow and BDF. Then both of these solutions are compared with results of two different reservoir numerical simulators, ECLIPSE 100 and IMEX-CMG. The conclusions that were made from this study are presented in the last section. Περίληψη: Σκοπός αυτής της διπλωματικής ήταν να διαμορφώσει απλές και εύκολες μεθόδους για την πρόβλεψη της μελλοντικής απόδοσης των μη συμβατικών ταμιευτήρων (σφιχτά και σχιστολιθικά) με γραμμική γεωμετρία ροής και εκτεταμένη παροδική ροή. Έτσι, προτάθηκε η μέθοδος CRM, προκειμένου να αξιολογηθεί γρήγορα κι εύκολα η απόδοση των ταμιευτήρων. Πιο συγκεκριμένα, περιγράφεται μια αναλογία μεταξύ της ηλεκτρικής και της πετρελαϊκής μηχανικής και εισάγονται δύο όροι (χωρητικότητα και αντίσταση). Η διαδικασία περιλαμβάνει έναν απλό συνδυασμό εξισώσεων αρχής διατήρησης της μάζας, της ερευνηθείσας απόστασης και της επικρατούσας ροής, χρησιμοποιώντας την έννοια της συνεχούς διαδοχής των ψευδο-σταθερών καταστάσεων. Ακολούθως συζητείται το βασικό μοντέλο, το οποίο αποτελείται από έναν ορθογώνιο ομοιογενή ταμιευτήρα με ένα φρέαρ τοποθετημένο στο κέντρο του και μία υδραυλική ρωγμάτωση να το διασχίζει, μέχρι τα όρια του ταμιευτήρα. Αυτή η διαδικασία χρησιμοποιείται κατά τη διάρκεια της παροδικής και οριοθετημένης ροής των ταμιευτήρων, όταν χρησιμοποιείται η εξίσωση της ερευνηθείσας απόστασης. Η μέθοδος αντίστασης - χωρητικότητας (CRM) είναι παρόμοια με τις εμπειρικές μεθόδους, διότι και οι δύο χρησιμοποιούν ελάχιστα δεδομένα σε σύγκριση με τις αναλυτικές μεθόδους και αυτό το χαρακτηριστικό τις καθιστά τόσο επιθυμητές. Παρόλο που οι εμπειρικές μέθοδοι δεν έχουν φυσική βάση, η μέθοδος CRM χρησιμοποιεί την εξίσωση της αρχής διατήρησης της μάζας, ακριβώς όπως κάνουν οι αναλυτικές μέθοδοι. Ως εκ τούτου, οι κλασσικές έννοιες χρησιμοποιούνται για να επιδείξουν μια γρήγορη, εύκολη και φθηνή μέθοδο. Με αυτό τον τρόπο η CRM έχει μια φυσική βάση σε σύγκριση με τις εμπειρικές λύσεις και οι παράμετροί της έχουν φυσικό νόημα. Αυτό έχει ως αποτέλεσμα, η αυτή νέα μεθοδολογία να μπορεί να τοποθετηθεί ανάμεσα στις αναλυτικές και τις εμπειρικές μεθόδους, αξιοποιώντας τα πλεονεκτήματα της καθεμιάς. Μετά την ολοκλήρωση της διαδικασίας ανάπτυξης αυτού του νέου μοντέλου, τα αποτελέσματά του συγκρίθηκαν με τις αναλυτικά λύσεις. Οι τελευταίες χρησιμοποιήθηκαν για την επαλήθευση των αποτελεσμάτων, όπως αυτά προέκυψαν από τη CRM για δεξαμενές υγρών που παράγουν υπό σταθερή παροχή και σταθερή πίεση. Αυτές οι λύσεις χρησιμοποίησαν την αδιάστατη εξίσωση της διάχυσης και συγκεκριμένες διαφορετικές αρχικές και οριακές συνθήκες για έναν ταμιευτήρα συγκεκριμένων διαστάσεων προκειμένου να αποκτήσουν αναλυτικά τις λύσεις και να τις εκφράσουν σε πραγματικό χρόνο. Εφόσον οι αναλυτικές λύσεις είναι έγκυρες καθ’ όλη τη διάρκεια της παραγωγής, ως εκ τούτου μπορούν να χρησιμοποιηθούν τόσο για την μεταβατική όσο και για τη ροή που επικρατεί στο όριο του ταμιευτήρα (BDF). Τέλος, τα ληφθέντα CRM και τα αναλυτικά αποτελέσματα συγκρίθηκαν με τα αποτελέσματα γνωστών αριθμητικών προσομοιωτών (ECLIPSE και IMEX), αλλά για ταμιευτήρες υγρών με ποικίλες ιδιότητες κατά τη διάρκεια τόσο των παροδικών όσο και των BDF ροών. Παρόλο που όλα τα μοντέλα φαίνεται να είναι γενικά σε καλή συμφωνία μεταξύ τους, οι λύσεις όπως προέκυψαν από το ECLIPSE και το IMEX φαίνεται να είναι πιο κοντά, ενώ το μοντέλο CRM και το αναλυτικό μοντέλο είναι σε μεγαλύτερη συμφωνία μεταξύ τους παρά με τις αριθμητικές λύσεις προσομοίωσης. Λαμβάνοντας υπόψη όλα τα προαναφερθέντα, το CRM μπορεί να παρέχει γρήγορα και οικονομικά, εύλογα και αξιόπιστα αποτελέσματα της απόδοσης των ταμιευτήρων και μπορεί να χρησιμοποιηθεί ως αξιόπιστο εργαλείο στις προβλέψεις ανάκτησης υδρογονανθράκων.

Μεταπτυχιακή Διατριβή για το μεταπτυχιακά της σχολής Μηχανικών Ορυκτών Πορών, Μηχανικη Πετρελαιων (Petroleum Engineering), Πολυτεχνειο Κρητης Master Thesis Dissertation for the MSc of Petroleum Engineering, School Of Mineral Resources, Technical University of Crete Summarization: The Single-well Tracer Test is a test used extensively to measure the residual oil saturation- Sor in watered-out reservoir. Also, it is implemented in order to evaluate enhanced oil recovery (EOR) using chemicals, such as Alkaline/Surfactant/Polymer flooding. The tracer test, in particular, includes a water/oil partitioning tracer injection, along with water, to a radius of investigation of 30 feet around a test well. Then the well is shut in and the injected tracer, usually an ester, reacts with the formation water producing ethanol. The produced ethanol dissolves only in the water. When the well is again set on production, the produced water is measured regularly, in order to measure the concentration of the tracers; the remained unreacted ester, and the produced ethanol. Due to the fact that the ester is partitioning tracer and the ethanol is a passive tracer, a separation will be observed on the arrival of time that the peak concentration is measured. This separation gives the Sor estimation. A passive tracer is injected along with the ester, in order to monitor any losses of the injected volumes in the reservoir. During production the ester’s and the passive tracer’s peak concentration should arrive at the same time. The test is affected by several parameters, such as the reservoir temperature, the brine salinity and the temperature gradient that is created after the injection. The temperature affects the partitioning coefficient of the tracer in positive way, as also the reaction rate, with the same way. Brine salinity affects the partitioning coefficient in positive way, while the reaction rate of the tracer is affected negatively. In order to take into consideration initial temperature and brine effect, the part. Coefficient and the reaction rate are measured in the lab at reservoir conditions, using the formation water at the reservoir temperature. Furthermore, the injection is done with formation water in order to keep the salinity effect constant. The temperature effect, in terms of different reservoir and/or injection water temperature is examined, and also in terms of the different temperature gradient that is created using or not pre-flush water volume in order to cool down the reservoir. The reservoir temperature affects the results with the same way; more ethanol is produced, while the water temperature, affects the reaction only when pre-flush is used. Injection rate also affects the amount of the produced ethanol, with high injection rate to be optimal the test to be valid. Regarding the history matching conducted under the described scope and the temperature effects, better result were obtained when a pre-flush volume is injected. Also, more satisfying results were obtained with increasing the separate layers of the investigation interval. The final Sor estimation was not uniformly distributed though out the reservoir, varying from 10% to 26% at same cases. All simulations were done using the Chemical Simulator of the University of Texas (UTCHEM).

Diploma thesis for the Msc Petroleum Engineering Summarization: This diploma thesis focuses on examining the fluid flow in a fractured reservoir, as well as the simultaneous flow of fracture/matrix systems. Fractured reservoirs have many differences comparing with the conventional ones. A reservoir might be naturally fractured, but also fracturing is a technique that is applied in the subsurface sediments, in order to improve the oil recovery during the production. In addition, there is an extensive description of the recovery mechanisms of a fractured reservoir, according to the literature, although it is still a complicated issue the way that the fractures contribute to the hydrocarbon recovery and the performance of a reservoir. Finally, it is mentioned the use of tracers applications in the oil field. Particularly, in this study, tracers are involved to understand and visualize, in some manner, the fluid flow in a fractured reservoir.