Scaling is one of the phenomenon during production from geothermal wellbores which should be continuously controlled and monitored in order to maintain stabilized production in geothermal fields. Its occurrence depends on both the... more
Scaling is one of the phenomenon during production from geothermal wellbores which should be continuously controlled and monitored in order to maintain stabilized production in geothermal fields. Its occurrence depends on both the characteristics of the field and saturation of minerals in brine phase and it causes to decrease of fluid production in wellbore in a short time. Calcium carbonate scaling is the most abundant type of scale along with Al, Mg and Fe minerals both in Turkey and the other geothermal fields around the world. Acidification or mechanical reaming are the cleaning processes of the scale which deposited due to the thermodynamic changes in the wellbore. Instead of cleaning processes, inhibitors are active used in geothermal fields to prevent scaling nowadays. Inhibitor application has started to prevent scaling in production wells in Kızıldere Geothermal Power Plant since 2009. Common inhibitor types are phosphonates with different salts and polymer products in geot...
In Kızıldere Geothermal Field, there were 25 drilled wells until 2009, 9 of which are currently being produced for 15 MWe GPP now. After the evaluation of geological and geophysical exploration studies conducted at the field, new well... more
In Kızıldere Geothermal Field, there were 25 drilled wells until 2009, 9 of which are currently being produced for 15 MWe GPP now. After the evaluation of geological and geophysical exploration studies conducted at the field, new well locations were determined for the planned new power plant. The drilling work commenced in November 2009 and as of January 2011, 11 wells are completed. In this regard, geochemical sampling, tests and measurements are performed at two phase fluids: Chemical, stable isotope samplings are realized for brine, while gas samples are taken for NCG and 13C-CO2 isotope and steam condensate sampling are conducted for gas/steam phase. For the determination of Gas/Gas+Steam ratio in-situ, measurements are performed at steam phase. Geochemical characterization of wells mainly depend on different reservoirs in Kızıldere Geothermal Field.
Calcite scaling is widely encountered in geothermal wells and it has to be inhibited since it prevents production. As a result of a pressure drop, thermal fluids start to boil and degas of CO 2 while fluids rise in a wellbore. Thermal... more
Calcite scaling is widely encountered in geothermal wells and it has to be inhibited since it prevents production. As a result of a pressure drop, thermal fluids start to boil and degas of CO 2 while fluids rise in a wellbore. Thermal fluid becomes saturated to calcite as a result of both CO 2 exsolution and concentration increase of calcium and carbonates as a consequence of boiling. When the first gas bubble is formed, CO 2 exsolution affects the ph and also carbonate species. In order to prevent calcite scaling effectively, inhibitor must be injected into the wellbore at a depth below gas breakout point where thermal fluid is still in liquid phase. Thermal fluid transforms from 100% liquid to both liquid and gas phases at the gas breakout depth when the sum of partial pressures of water vapor and non-condensable gases exceed the wellbore pressure under flowing conditions. There are a lot of ways to predict the gas breakout depth in geothermal wellbores. One of them, the easiest b...
Geothermal well testing is the only way of investigating the physical properties of the reservoir rock as well as the dynamic properties of the fluid flowing both through the wellbore and the reservoir. It is known that Petroleum and... more
Geothermal well testing is the only way of investigating the physical properties of the reservoir rock as well as the dynamic properties of the fluid flowing both through the wellbore and the reservoir. It is known that Petroleum and Geothermal fluids have similar properties in terms of well testing. In this regard, almost every test or approach used in Petroleum industry can be applied to geothermal well testing. Among these tests, DST (drill stem test) is the most commonly known one in terms of its applicability and reliability. Other well-known tests for geothermal well testing include static and dynamic TPS (temperature, pressure and spinner) surveys and geochemical analysis of the flowing fluid play. The data which can be acquired from these tests include productivity, flowing fluid properties, flow capacity, pressure and temperature. All other necessary results and information regarding the reservoir conditions can be estimated from these basic of data.
Sampled aqueous chemistry at surface, is altered from reservoir chemistry due to boiling, degassing of non-condensable gases (mostly CO2), and conductively or adiabatically cooling in wellbore at water dominated geothermal field.... more
Sampled aqueous chemistry at surface, is altered from reservoir chemistry due to boiling, degassing of non-condensable gases (mostly CO2), and conductively or adiabatically cooling in wellbore at water dominated geothermal field. Geochemical modelling studies, from reservoir to surface or reinjection, begin by computing the initial equilibrium state of the system at temperature and pressure of geothermal reservoir. Practically, however, physical and chemical properties of fluid in reservoir cannot be measured. Therefore, in such cases, fluid chemistry is calculated from chemical analysis of surface samples. Consequently, some geochemical calculation steps should be combined to estimate reservoir chemistry. Aqueous chemical analysis reveals just bulk composition of the solution. In order to distribute bulk composition among concentrations of ionic and molecular species, speciation step should be conducted. This process is the first step of the geochemical calculation workflow. Following steps are; mixing, increasing temperature, dissolution and equilibration. In this paper, governing equations that used in geochemical calculations and computation sequence of geochemical models are introduced to estimate reservoir fluid chemistry.
Typically, geothermal wellbore model is used to predict the production performance of wells using a wellbore simulator based on flow tests. An iterative procedure is used to calibrate NCG content. In this study, a predictive modelling... more
Typically, geothermal wellbore model is used to predict the production performance of wells using a wellbore simulator based on flow tests. An iterative procedure is used to calibrate NCG content. In this study, a predictive modelling approach harnessing the power of machine learning is proposed. Several deep well data in Kizildere Geothermal Field have been used to calibrate the model. The results are compared to flowmeter data attached to a mini separator. It has been observed that flowmeter NCG results are consistent with predictive modelling results in most of the wells. Since NCG measurements with mini separator are challenging, it is possible to predict NCG values for the wells without actual measurements at the wellsite.
Tracer tests are commonly carried out in geothermal fields in order to model certain parameters of the reservoir part between the production and injection wells and to predict the response of the reservoir to production. To obtain... more
Tracer tests are commonly carried out in geothermal fields in order to model certain parameters of the reservoir part between the production and injection wells and to predict the response of the reservoir to production. To obtain meaningful data in wells with weak hydraulic connection to each other, tracer tests need to be performed over long periods of time using large quantities of chemicals which have sufficient thermal stability. In such cases, tracer tests can be very costly and even after long periods, sufficient tracer amount needed for interpretation may not be obtained from the production wells. On the other hand, components such as chloride, which have conservative properties and are naturally present in the reservoir, can also be used as tracers.
This study was done as preliminary work for both artificial tracer tests and water-rock interaction modeling studies which are going to be conducted in the GECO project. GECO (Geothermal Emission Control) is an EU funded project through the Horizon 2020 and aims to develop near Zero Emission Geothermal Power Plants. Within the scope of the GECO project, a pilot CO2 injection in the KD50A well will be carried out for greener geothermal energy production in the Kızıldere geothermal field. The objective of this study is to evaluate the flow paths between KD50A and surrounding production wells by using chloride as natural tracer.
The reservoir in Kızıldere geothermal field is water dominated. However, pressure dropping in the fluid gathering system (wellbores and separator units) causes gas formation along with boiling and adiabatic cooling. Because of the boiling, dissolved chloride concentration in the water increases. After harvesting steam and heat from the geothermal fluid, the effluent water is re-injected into the same reservoir with an increased chloride concentration. Thus, the magnitude of changes observed in chloride concentration in production wells reflects the degree of connectivity between production and injection wells and provides chloride to be used as a tracer. An analytical solution for 1D transport equation was used in modelling chloride concentration. Velocity, dispersivity and length of flow paths were calibrated with observed chloride concentrations at production wells.
According to the model results, velocities and dispersivities of the flow paths are in range between 0.62-2.87 m/day and 48-236 m2/day, respectively. Chloride is conservative and occurs naturally in almost all reservoirs. For this reason, the interaction of production and re-injection wells can be evaluated using chloride in geothermal fields where flash-type power plants are installed or in power plants where condensed steam does not mix with re-injection water.
Predictive modeling of flow and transport processes in geothermal reservoirs is difficult due to the complex nature of fracture networks. Tracer tests are traditionally used to characterize geothermal reservoirs for sustainable injection... more
Predictive modeling of flow and transport processes in geothermal reservoirs is difficult due to the complex nature of fracture networks. Tracer tests are traditionally used to characterize geothermal reservoirs for sustainable injection and production strategies. Interpretation of tracer tests to obtain accurate flow parameters is usually carried out using simplified one-dimensional or two-dimensional mathematical analytical models. However, these models provide uniform flow parameters that are not suitable for fractured and porous geothermal reservoir characterization due to anisotropy and macrodispersion. In this study, a tracer test was analyzed to characterize and predict the thermal breakthrough time of a geothermal reservoir located in western Turkey. A new analytical model was developed for the analysis of tracer tests conducted, and combined with a statistical algorithm to obtain well-to-well parameters. In addition, the permeability parameters of the reservoir were estimated based on the mud-loss and well test data. Afterward, the results were compared. The comparison results show that the statistical method combined with the developed analytical model provides robust assessments of reservoir parameters in fracture reservoir systems with anisotropic flow paths.
