PREDICTIVE MODELING OF CO2 – BRINE CO-INJECTION CONDITIONS IN RE-INJECTION WELLS

Emissions of greenhouse gases such as CO2 emitted at Turkish geothermal power plants are an obstacle to call geothermal energy as green power. However, recent advances in carbon capture and storage technologies have enabled low emissions by re-injecting produced CO2. The phase of injected CO2 is crucial for the success and safety of the operation. Injecting CO2 directly into a reservoir as pure gas or at supercritical state may cause the leakage of CO2 via fractures, or abandoned wells. This problem can be prevented by the dissolution of CO2 into brine prior to, or during its injection into the reservoir. Various projects have been being conducted around the world to reduce geothermal emissions. Among these projects, GECO (Geothermal Emission Control) is an EU funded project through the Horizon 2020 and aims to develop near-zero emission geothermal power plants. Through the GECO project, Zorlu Energy and METU (Turkey) aim to reduce the CO2 emissions for more green geothermal power production while maintaining the sustainability of Kızıldere (Turkey) geothermal field (KGF).The objective of this study is to calculate possible ranges of CO2 molar ratios to ensure all injected CO2 will dissolve in brine and preclude the gas formation in re-injection wells at KGF. In order to compute partial pressures of dissolved CO2 at elevated temperatures for a given CO2 molar ratio, chemical analysis of injection water was defined as a solution in PHREEQC and various amounts of CO2 were irreversibly added into the solution. Temperature range in geochemical modeling was selected from injection temperature at the well head and static temperature at reservoir level of the boreholes. Pressure profiles of the wells were calculated by assuming hydrostatic condition. The model results showed that the dissolved CO2 in the wellbore should not exceed 0.75 mole per kg water during injection. It was concluded that injection flow rates of both water and gas phases should be arranged with this constraint

Mining-Assisted Heavy Oil Production (MAHOP)

This research aims to investigate and compare the ultimate recovery from the largest oil reserve in Turkey (1.85 billion barrels) using a new method called mining-assisted heavy oil production (MAHOP) with conventional SAGD. Tunnels will be excavated from the surface to the reservoir. Fan-shaped up holes will then be drilled in the reservoir from the tunnels.Heavy oil production through these tunnels will be explored using SAGD method. Several numerical models have been designed using CMG’s STARS simulator. Since the fan wells are opened vertically and at certain intervals along the tunnel, both a tight vertical fracturing of these wells and a separate fracture network formed by micro fractures in the vicinity of the fan holes are formed.The validation of these hypotheses has been conducted in CMG which showed that MAHOP gave better results compared to conventional SAGD where two horizontal wells are used. MAHOP gave better recovery values with less steam oil ratios. With the results of the simulation study a laboratory model was designed. Experimental operational parameters using three different wettability cases were simulated to observe recovery by considering several possible physical effects such as steam distillation and in-situ upgrading. Saturation and pressure distributions were also obtained

Numerical reservoir simulation of Alaşehir geothermal field

Use of a comprehensive reservoir simulation is essential for an effective geothermal reservoir management. TOUGH2 has become a widely used simulator for this purpose. In this study, one of the most exploited geothermal fields in Turkey, Alaşehir geothermal field has been modeled by using TOUGH2 reservoir simulator. The study includes more than 100 wells, which are operated by 7 different developers. The total installed capacity of geothermal power plants in the field is 212 MWe, but additional capacity (98 MWe) is planned to be commissioned by the end of 2020. The proximity of licensed areas and strong well interferences have made the simulation necessary for a successful reservoir management. Different data sources including pressure transient tests, reservoir monitoring and tracer test data were coupled to construct a large numerical model, which has dimensions of 18 kmx12kmx5.5km. During model calibration, good matches were obtained between model results and actual decline in the reservoir temperature, pressure and noncondensable gases (NCG) production. The effect of planned power plants on the field performance is studied by performing scenario runs using maximum possible flow rates. Model results indicated that commissioning of new power plants and additional make up wells that will compensate missing production accelerates pressure decline to more than 3 bars/year

Near Critical Gas Condensate Relative Permeability of Carbonates

Typical gas condensate fields contain a gas/liquid system during depletion. Such systems are difficult to model experimentally because they exhibit near-miscible behavior at high pressure and temperature. One way to simplify laboratory experimentation is to use a binary retrograde condensate fluid and to adjust temperature to control miscibility. A series of relative permeability test were conducted on a moderate-permeability carbonate core using methanol/n-hexane at near miscible conditions in the presence of immobile water. Potassium carbonate was added to the water to prevent miscibility with methanol. The experiments used a pseudo-steady-state technique under conditions similar to the near well region of a carbonate gas-condensate reservoir. The flow of gas and condensate at different force ratios was investigated. Relative permeabilities were obtained by matching historical production and pressure data using a coreflood simulator. It was observed that relative permeability depended on fluid composition and flow rate as well as initial condensate and water saturations. As the wetting phase (condensate) flow rate increased or interfacial tension decreased, relative permeability versus wetting phase saturation curves shifted towards lower wetting phase saturations. It was found that a simple three-parameter mathematical model that depends on a new dimensionless number called condensate number successfully modeled the gas-condensate relative permeability data. The developed model resulted in a good agreement with published gas-condensate relative permeability data as well as end point relative permeabilities and saturations. The relative permeability behavior as a function of IFT highly resembles the one observed in sandstones

Experimental Investigation of the Effect of Temperature on Friction Pressure Loss of Polymeric Drilling Fluid Through Vertical Concentric Annulus

Accurate estimation of annular friction pressure loss is necessary to perform drilling and well completion operations without lostcirculation, pipe sticking or more serious well control problems. Determination of friction pressure loss for Newtonian and non-Newtonianfluids has been investigated in several experimental and theoretical works by considering the effects of eccentricity, pipe rotation or pipegeometry. However, there is a gap in the studies about the temperature effect that is important especially in geothermal wells.This study experimentally investigated the effect of temperature on friction pressure loss through vertical concentric annulus by usingwater and the polymer based drilling fluid including Polyanionic Cellulose and Xanthan Gum. Experiments were conducted in flow loophaving 21-ft smooth and concentric annular test section (2.91 in ID casing x 1.85 in OD pipe).The effect of temperature on rheological model parameters, apparent viscosity, Reynolds number was examined. It was found thatconsistency index and yield point were more sensitive to change in temperature than flow behavior index. Also, apparent viscositydecreased exponentially with increasing temperature and this decrease was more obvious in low shear rate values. Then, according toReynolds number – temperature plot, earlier regime transition was observed with increasing temperature.As a result, increasing temperature caused the decrease in friction pressure loss, and temperature effect should be considered in futureexperimental and theoretical studies in order to estimate friction pressure loss in annuli precisely

Başarı Yönelimleri ile Kararlılık Arasındaki İlişkiler

The present study aims to investigate the associations of achievement goal orientations with grit. Participants were 509 university students who completed The 2X2 Achievement Goal Orientations Scale and Grit Scale. This relationship was investigated using correlation and multiple regression analysis. According to results learning-approach goal orientations positively related to grit. In contrary, learning-avoidance and performance-approach/avoidance goal orientations related negatively to grit. Students who adopt learning-approach goal orientation are more likely to have higher level of grit.Bu araştırmada başarı yönelimleri ile kararlılık arasındaki ilişkiler incelenmiştir. Araştırma 509 üniversite öğrencisinde üzerinde yürütülmüştür. Katılımcılara 2X2 Başarı Yönelimleri Ölçeği ile Kararlılık Ölçeği uygulanmıştır. Başarı yönelimleri ile kararlılık arasındaki ilişkiler korelasyon ve çoklu regresyon analiziyle incelenmiştir. Korelasyon ve regresyon sonuçları öğrenme-kaçınma, performans-yaklaşma/kaçınma alt boyutlarının kararlılık ile negatif, öğrenme-yaklaşma boyutunun ise pozitif ilişkili olduğunu ortaya koymuştur. Elde edilen bulgular litaretür doğrultusunda tartışılmıştır

LIQUEFACTION OF NIGDE-ULUKISLA OIL SHALE: THE EFFECTS OF PROCESS PARAMETERS ON THE CONVERSION OF LIQUEFACTION PRODUCTS

In this paper, the direct liquefaction of Turkish Nigde-Ulukisla oil shale in noncatalytic and catalytic conditions was studied. The effects of pressure, tetralin/oil shale ratio, catalyst type and concentration, reaction time and temperature and oil shale/waste paper ratio on the process were investigated. It was found that tetralin/oil shale ratio had no considerable effect on the total and liquefaction products conversions under the noncatalytic conditions. Fe2O3, MoO3, Mo(CO)(6), Cr(CO)(6) and zeolite were used as catalysts in catalytic liquefaction. The highest total and liquefaction products conversions were obtained using MoO3 as catalyst at a concentration of 9% by weight. Reaction temperature of 400 degrees C and reaction time of 90 minutes were chosen according to obtained liquefaction results. Co-liquefaction experiments were performed using waste paper. Both the total and oil + gas conversions were increased to a considerable extent by the application of the co-liquefaction process. According to gas chromatographic-mass spectrometric (GC-MS) analysis, the liquid product from the liquefaction process of oil shale under catalytic conditions of experiment 22 consisted mainly of naphthalene and its derivatives and polycyclic hydrocarbon such as indene and its derivatives

Artificial Lifting in Liquid Dominated High-Temperature Geothermal Fields in Turkey: Lessons Learned

Due to the attractive feed-in-tariff mechanism, Turkish geothermal producers operate geothermal power plants at their maximum capacity. As a result, many geothermal reservoirs in Turkey have been exploited with an aggressive production strategy by multiple operators. A significant amount of production targeted natural fractures associated with normal faults in Western Anatolia. Wells produced at the maximum allowable capacity caused substantial reservoir pressure drops that affected reservoir dynamics. Premature temperature decline, local pressure drop, and the sharp decline of non-condensable gases (NCG) have been commonly observed in these geothermal reservoirs. All of these impacted the production performance of wells negatively. Artificial lifting methods such as airlifting and downhole pumps (Line shaft pumps or electrical submersible pumps (ESPs)) are commonly used to compensate for missing production. This study discusses the use of ESPs in liquid dominated high-temperature Alaşehir and Kızıldere fields. Observations, experiences, and lessons learned from the ESP applications in these fields are reported in detail

Je li fleksibilna bronhoskopija siguran postupak kod kritičnih bolesnika s respiracijskim zatajanjem?

Flexible bronchoscopy (FB) plays an important role in critical care patients. But, critical care patients with respiratory failure are at an increased risk of developing complications. Considering the developments in intensive care unit care in recent years, we aimed to evaluate the use of FB in these patients. We retrospectively reviewed patients who underwent FB in critical care between 2014 and 2020. A total of 143 patients underwent FB during the study period. Arterial blood gas measurement on the FB day revealed a mean PaO2/FiO2 of 186.94±28.47. Eighty-one (56.6%) patients underwent an fiberoptic bronchoscopy procedure under conventional oxygen supplementation, 10 (7%) on noninvasive ventilation, 13 (9.1%) on high flow nasal cannula, and 39 (27.3%) on invasive mechanical ventilation. During and immediately after bronchoscopy, none of the patients experienced life-threatening complications. Fifty-five (38.5%) patients developed complications that could be controlled. Multivariate analysis indicated that increased Apache-II score and presence of cardiovascular disease were significantly associated with an increased complication risk. Although critical care patients with respiratory failure are more prone to complications, diagnostic and therapeutic bronchoscopy may be performed following appropriate patient selection, without leading to major complications.Fleksibilna bronhoskopija (FB) igra važnu ulogu u bolesnika na kritičnoj skrbi. Međutim, ovi bolesnici na kritičnoj skrbi s respiracijskim zatajenjem imaju povećani rizik od razvoja komplikacija. S obzirom na napredak u skrbi u jedinici intenzivnog liječenja tijekom posljednjih godina cilj je bio procijeniti uporabu FB-a u ovih bolesnika. Retrospektivno smo pregledali podatke bolesnika koji su podvrgnuti FB-u u kritičnoj skrbi između 2014. i 2020. godine. Ukupno je 143 bolesnika podvrgnuto FB-u tijekom razdoblja ispitivanja. Mjerenje plinova u arterijskoj krvi na dan FB pokazalo je srednju vrijednost PaO2/ FiO2 od 186,94±28,47. Osamdeset jedan bolesnik (56,6%) podvrgnut je postupku fiberoptičke bronhoskopije pod konvencionalnim dodacima kisika, 10 (7%) na neinvazivnoj ventilaciji, 13 (9,1%) na nosnoj kanili s velikim protokom i 39 (27,3%) na invazivnoj mehaničkoj ventilaciji. Tijekom i neposredno nakon bronhoskopije niti jedan bolesnik nije doživio komplikacije opasne za život. Osim toga, 55 (38,5%) bolesnika razvilo je komplikacije koje se mogu kontrolirati. Prema multivarijatnoj analizi, povećani rezultat Apache-II i prisutnost kardiovaskularnih bolesti bili su značajno povezani s povećanim rizikom od komplikacija. Iako su bolesnici na kritičnoj skrbi s respiracijskim zatajenjem skloniji komplikacijama, dijagnostička i terapijska bronhoskopija mogu se provesti nakon odgovarajućeg odabira bolesnika, a da to ne dovede do većih komplikacija