Ender Okandan

Assessment of energetic heterogeneity of coals for gas adsorption and its effect on mixture predictions for coalbed methane studies

Abstract This study explains the single-component and binary mixture adsorption studies on two different coals from the Zonguldak Basin (Northwestern Turkey). Assessment of energetic heterogeneity of coal surface and its effect on the equilibrium binary gas adsorption are discussed. Single component adsorption tests were performed using methane and carbon dioxide at 30°C. Binary mixtures prepared with 10, 15 and 20% carbon dioxide were also tested at the same temperature. Various single-component adsorption isotherms were fitted to the experimental data of single gases. The data obtained from these models were interpreted to determine the energetic heterogeneity of the coals towards adsorption of methane and carbon dioxide. Ideal adsorbed solution (IAS) theory was used to predict the data and discrepancies between experimental data, and the model predictions were interpreted. Results showed that coals exhibit a heterogeneous behavior in gas adsorption. This heterogeneity can be different for each coal–gas pair and the extent of the heterogeneity makes the binary gas predictions differ from the experimental data. The deviations between IAS and experimental data increase as the amount of gas, to which the coal shows high heterogeneity, increases in the mixture.

Effect of crude oil type and heating rate on combustion of crude oil-lignite mixtures

Research was conducted to investigate the possibility of upgrading low-quality lignites by mixing them with heavy crude oils. Three crude oil samples with API gravities of 12.9, 18.7 and 26.7 were mixed with lignite to form mixtures of 10 and 20% oil content. Thermal analysis experiments were conducted at non-isothermal heating conditions at heating rates of 5–100 K min−1. Differential thermogravimetric data were analysed using an Arrhenius-type reaction model assuming a first-order reaction. The results indicate that the combustion of mixtures as observed on thermograms is very similar to that of lignite. However, the activation energy and reaction peak temperatures increased as the oil content in the mixture increased.

Kinetic analysis of in situ combustion processes with thermogravimetric and differential thermogravimetric analysis and reaction tube experiments

Abstract This research comprises the determination of kinetic parameters of in situ combustion processes by reaction tube and thermal (thermogravimetric analysis (TGA)/differential thermogravimetric analysis (DTGA)) experiments. A previously developed laboratory model and a Du Pont 9900 thermalanalyzer unit were used to run the experiments. Three reaction regions for combustion of crude oil in porous media were observed in the reaction tube and TGA/DTGA experiments and are defined as low temperature oxidation, fuel deposition and high temperature oxidation. The kinetic parameters are calculated for each reaction region using Weijdemas reaction model in reaction tube experiments. The Arrhenius model is applied to determine the kinetic parameters from TGA/DTGA thermograms and a comparison is made between kinetic results.

Thermal analysis of crude oil-lignite mixtures by differential scanning calorimetry

Abstract Thermal characterization of lignite, crude oils and their 10 and 20% mixtures were investigated by differential scanning calorimetry (d.s.c.). The calorific value of the lignite increased in mixtures depending on the crude oil type. In pyrolysis runs, temperature ranges where distillation and visbreaking occur were identified for the crude oils studied. The effect of heating rate was also studied, and higher reaction temperatures and higher heat flow rates were observed at d.s.c. peak thermograms with increasing heating rate (5, 10, 15, 20 and 25 °C min−1). The specific heat of samples was examined in the temperature range 20–600 °C, and showed an increase with increasing temperature until the decomposition temperature was reached. Kinetic parameters of the samples were investigated and an increase was observed in the activation energy and Arrhenius constant of the mixtures.

The use of chemical inhibitors for prevention of calcium carbonate scaling

Abstract An experimental study on calcium carbonate scaling and prevention by chemical inhibitors was carried out in a laboratory model. In order to study the inhibiting capacities of the chemicals, experiments were performed with four different inhibitors by flashing 350 cc of 0.1 M Ca++ solution to atmospheric pressure at a temperature of 144 °C. The partial pressure of C02 was 3.6 MPa. The performances of inhibitors with different concentrations were analyzed in terms of the amount of scale formed. The results showed that the amount of scale was reduced, but not totaly prevented and after a certain inhibitor concentration it increased again which was interpreted as the formation of a pseudo-scale. Then the process was tested with different calcium concentrations in solution and partial pressures of carbon dioxide. Amount of deposited calcite increased with the increase of these two parameters.

Heterogeneity Effects on the Storage and Production of Gas from Coal Seams

This paper presents the results of the experiments conducted on two structurally different coals from Turkey to investigate the effect of different heterogeneities on gas flow and storage in coal beds. Gas flow experiments were conducted on 3.8 cm diameter core plugs of these coals using xenon as the gas phase. Dual energy CT imaging technique was used to visualize the flow and storage of gas along the coal core to get qualitative and quantitative data from the images. After storage experiments end, nitrogen injection was performed to recover the stored gas from coal to represent an enhanced gas recovery operation. An analytical solution to this phase of one specific experiment was proposed to be able to calculate the diffusion coefficients from the gas recovery data calculated from CT images. The results of the experiments were analyzed to show the storage capacities of these two coals. The effect of different coal structures on the gas transport and storage and the matrix/fracture interactions were discussed by making a pixel based analysis and coupling it with the microstructure of coal investigated with scanning electron microscopy (SEM). Results show that, if the coal is structurally heterogeneous in the sense that there will be different layers of mineral and organic matrix, there will be different zones that affect the storage and transport of gas. Due to these heterogeneities, gas recovery by nitrogen injection is not efficient at some regions. On the other hand, the coal that is more homogeneous has a higher storage capacity due to its microporous structure. In this coal, even if there are mineral fillings in the micropores, such mineral inclusions do not have an adverse effect on gas storage and transport as evidenced from CT images.

Pollution of an Aquifer by Produced Oil Field Water

Brine is produced from reservoirs as a waste material from crude oil and gas after processing. Waste water may be discharged at the surface or reinjected underground. When it is reinjected, it may be mixed with an underground fresh water source for several reasons. From this point of view, forecasting the pollutant concentrations by knowing the historical data at several locations on a field has great importance when planning the necessary precautions for environmental safety. Aquifer-M in Turkey, having the properties of potable water, is contaminated by oil field water that is injected for disposal purposes. A numerical model is used to determine the extent of pollution due to the injection of saline produced water into aquifer-M. Eight observation wells are drilled to take water and core samples in order to identify both rock and fluid properties of aquifer-M. Water samples taken from different intervals of aquifer-M are analyzed to determine the flow paths for the pollutant movement. The results are interpreted with the help of core property data obtained by computerized tomography (CT) analysis and routine core analysis. By using drilling records, log data, and CT analysis results, two subunits in aquifer-M with different lithological properties are identified. All data are used in a ground water pollution model. Aquifer-M has fresh water with salinity of 5-10 ppm, and the chlorine concentration of injected waste water is approximately 3410 ppm. Since there is a significant difference between these concentrations, the chlorine ion is selected as the indicative ion for locating the pollution front. The model study indicated that the contaminated water has propagated 18.7 km from the site of injection.Brine is produced from reservoirs as a waste material from crude oil and gas after processing. Waste water may be discharged at the surface or reinjected underground. When it is reinjected, it may be mixed with an underground fresh water source for several reasons. From this point of view, forecasting the pollutant concentrations by knowing the historical data at several locations on a field has great importance when planning the necessary precautions for environmental safety. Aquifer-M in Turkey, having the properties of potable water, is contaminated by oil field water that is injected for disposal purposes. A numerical model is used to determine the extent of pollution due to the injection of saline produced water into aquifer-M. Eight observation wells are drilled to take water and core samples in order to identify both rock and fluid properties of aquifer-M. Water samples taken from different intervals of aquifer-M are analyzed to determine the flow paths for the pollutant movement. The results are i...

CHANGE OF PHYSICAL AND THERMAL DECOMPOSITION PROPERTIES OF IN SITU HEAVY OIL WITH STEAM TEMPERATURE

ABSTRACT Ikiztepe crude oil was subjected to four different steam temperatures during steam injection which was applied as an enhanced oil recovery process on a linear limestone model saturated with oil. Produced oils were characterized using density, viscosity measurements, pyrolysis experiments utilizing TGA and elemental analysis runs. Results showed that produced crude oils change in measured characteristics as compared to the original oil. These changes include an increase in H/C, and cracking activation energy, decrease in density, viscosity and amount of residue remaining after cracking (coke). Also, decrease in asphaltene amount, changes in the elemental composition of asphaltenes and increase in the cracking activation energies were observed at 225 °C run. These measurements show that the produced oils get lighter and differ compositionally from the original oil as steam temperature increases. Decrease in elemental sulphur amount is one of the major changes when environmental considerations are c...

Field development and power generation in Kizildere, Turkey

Abstract Turkey is classified among the countries which have a high geothermal energy potential (Alpan, 1974). Geological and geophysical exploration is continuing in promising areas. However primary emphasis has been given to Western Anatolia during the last decade. As a result of these efforts Kizildere field was developed and a power plant put into operation on February 14, 1984. This paper summarizes the power plant and production problems encountered in wells during 1984 and future field development plans.

PT community meet in Istanbul: proficiency testing workshop

The historic city of Istanbul, known for where the East meets the West, became the meeting place for the global proficiency testing (PT) and external quality assurance (EQA) community for 4 days in October 2011. This was the 7th international PT workshop on Proficiency Testing in Analytical Chemistry, Microbiology and Laboratory Medicine organized by the EURACHEM Proficiency Testing Working Group in association with EQALM and CITAC. The workshop was supported locally by several Turkish organizations including the Middle East Technical University (METU), the Petroleum Research Center, EURACHEM-Turkiye, TUBITAK UME and TURKAK. The wonderful setting on the coast of the Sea of Marmara provided the perfect location for this successful workshop which once again provided an excellent opportunity for providers, users and regulators of PT/EQA to come together to discuss a wide range of key issues across the three disciplines of analytical chemistry, microbiology and laboratory medicine. The 233 delegates attending from 54 different counties ensured a truly global perspective. Since the last (6th) PT workshop held in Rome during October 2008, there have been a number of developments in the field of proficiency testing, one of the most notable being the publication of ISO/IEC 17043, the new international standard for the competence of PT/EQA providers, addressing the requirements for the development and operation of PT/EQA schemes. This new standard has been adopted by the International Laboratory Accreditation Cooperation (ILAC) as the requirements against which PT/ EQA providers should be accredited. With the publication and its subsequent adoption by ILAC, this has led to an increase in the number of PT/EQA providers being accredited around the world. This workshop, therefore, specifically addressed the experiences of implementing ISO/IEC 17043 both from the views of the PT/EQA providers and the accreditation bodies. In addition to addressing the implementation of ISO/IEC 17043, this workshop focused on further developments in performance assessment in microbiology and qualitative schemes, the status and needs of PT/EQA in developing areas of the world and advancements in preand postanalytical PT/EQA. These important topics addressed at this workshop were explored and discussed through a series of lectures and working group discussions. The diverse range of international delegates attending from different sectors provided a beneficial environment for the cross-fertilization of ideas. The workshop was enriched further with 52 poster contributions covering a wide range of topics and experiences concerned with PT/EQA. In conjunction with the workshop, training sessions on ‘‘Establishing Traceability and Uncertainty of Assigned Values’’ and ‘‘Assisting Participants to Assess/Estimate Their Measurement Uncertainty Using PT Results’’ were provided. This latest workshop once again proved a great success thanks to the hard work of the local organizers, the quality of the presentations and posters and just as importantly the active participation of all the delegates leading to lively debate and fruitful discussions. We are pleased to provide the papers on many of the presentations, posters and working group discussions in this Topical Focus on PT/ EQA issue of the Journal. B. Brookman (&) LGC Standards Proficiency Testing, Bury, UK e-mail: Brian.Brookman@lgcpt.com