Geothermal Energy: Current Status in Turkey with EU Perspective

The world's growing energy demands carry the energy into an important stage. Crude oil will be able to supply increasing demand until peak world production is reached. Forecasts show that this peak time is about 2020. Turkey and the world will deplete economically recoverable fossil resources by the end of the 21st century. The energy gap caused by declining fossil resources has to be filled by expanding production of other sources. Geothermal energy is one of the most important options for filling this gap. Turkey is located in the Alp Himalayan Tectonic Belt and has high potential geothermally. In fact, Turkey is the seventh country in the world while the first country in Europe of the abundance of geothermal resources. In this article, the history and development of geothermal, its application, and current situations in the world and the situation in Turkey with European Union perspective are examined by giving the facts and statistical information for the last 10-year period

Predicting Frictional Pressure Loss During Horizontal Drilling for Non-Newtonian Fluids

Accurate estimation of the frictional pressure losses for non-Newtonian drilling fluids inside annulus is quite important to determine pump rates and select mud pump systems during drilling operations. The purpose of this study is to estimate frictional pressure loss and velocity profile of non-Newtonian drilling fluids in both concentric and eccentric annuli using an Eulerian-Eulerian computational fluid dynamics (CFD) model. An extensive experimental program was performed in METU-PETE Flow Loop using two non-Newtonian drilling fluids including different concentrations of xanthan biopolimer, starch, KCl and soda ash, weighted with barite for different flow rates and frictional pressure losses were recorded during each test. This study aims to simulate non-Newtonian fluids flow through both horizontal concentric and eccentric annulus and to predict frictional pressure losses using an Eulerian-Eulerian computational fluid dynamics (CFD) model. Computational fluid dynamic simulations were performed to compare with experimental data gathered at the METU-PETE flow loop and previous studies as well as slot flow approximation for the annulus. Results show that the computational fluid dynamic model simulations are capable of estimating frictional pressure drop with an error of less than 10% in most cases, more accurately than the slot equation

A Mechanistic Model for Predicting Frictional Pressure Losses for Newtonian Fluids in Concentric Annulus

A mathematical model is introduced estimating the frictional pressure losses of Newtonian fluids flowing through a concentric annulus. A computer code is developed for the proposed model. Also, extensive experiments with water have been conducted at Middle East Technical University, Petroleum and Natural Gas Engineering Department Flow Loop and recorded pressure drop within the test section for various flow rates. The performance of the proposed model is compared with computational fluid dynamics (CFD) software simulated annulus flow section and various criteria such as crittendon, hydraulic diameter and slot flow approximation as well as experimental data. The results showed that the proposed model and experimental results are in good agreement for almost all cases when compared with the other criteria and CFD software. Also, the proposed model could estimate the frictional pressure losses for both laminar and turbulent flow regimes within an error range of +/- 10%

Friction factors for hydraulic calculations considering presence of cuttings and pipe rotation in horizontal/highly-inclined wellbores

Pressure loss calculations have a vital role for determining hydraulic horsepower requirements and to predict bottomhole treating pressure. One of the major concerns in developing hydraulic programs is to estimate the frictional pressure losses while cuttings are present in the annulus during pipe rotation. An experimental work has been carried out in a cuttings transport flow loop capable of operating at various inclinations. The pressure drop in the test section was recorded for variable flow rates, cuttings concentrations, pipe inclinations and rotation speeds. Existence of cuttings increase the pressure drop due to decrease in flow area inside the wellbore. As there are cuttings in the system, pipe rotation decreases the frictional pressure loss considerably in particular if the pipe is making an orbital motion in the eccentric annulus. Cuttings bed thickness defined as the ratio of cuttings bed area to the wellbore area is expressed in terms of dimensionless parameters obtained from dimensional analysis. Empirical expressions and charts for friction factor are proposed for low and high viscosity fluids in terms of combined Reynolds number and stationary cuttings bed thickness

Hole Cleaning Performance of Light-Weight Drilling Fluids During Horizontal Underbalanced Drilling

Hole cleaning is a major consideration at both the design and application stages of a drilling operation. If the fluid velocity is lower than a critical value at horizontal or high inclinations, a stationary bed develops which may cause various problems, such as high drag, higher probability of stuck pipe and higher hydraulic requirements, etc., if not removed properly. Therefore, this becomes important and essential to identifying critical velocity. This study aims to estimate the critical fluid-flow velocity for preventing the development of a stationary bed using empirical correlations that can be used easily at the field. Also, a rough estimation of bed thickness is introduced if the flow velocity is lower than the critical velocity. For this purpose, extensive cuttings transport experiments with water, called the Cuttings Transport Flow Loop, were conducted by the Petroleum and Natural Gas Engineering Department at Middle East Technical University (METU) in order to determine various inclinations, flow rates and rate of penetrations. The inner pipe is subject to a sagging, therefore more realistic annulus representation is achieved. Observations showed that a stationary bed can be developed even when the inclination of the wellbore is down to 50 degrees. Results showed that the critical velocity could be estimated using the proposed correlations with reasonable accuracy when compared with the experimental results. Also, for flow velocities less than the critical values, the thickness of the stationary bed can be detected mostly within an error range of +/- 15%

Modeling and Experimental Study of Newtonian Fluid Flow in Annulus

A major concern in drilling operations is the proper determination of frictional pressure loss in order to select a mud pump and avoid any serious problems. In this study, a mechanistic model is proposed for predicting the frictional pressure losses of light drilling fluid, which can be used for concentric annuli. The experimental data that were available in the literature and conducted at the Middle East Technical University-Petroleum Engineering (METU-PETE) flow loop as well as computational fluid dynamics (CFD) software are used to verify the results from the proposed mechanistic model. The results showed that the proposed model can estimate frictional pressure losses within a +/- 10% error interval when compared with the experimental data. Additionally, the effect of the pipe eccentricity on frictional pressure loss and tangential velocity using CFD for laminar and turbulent flow is also examined. It has been observed that pipe eccentricity drastically increases the tangential velocity inside the annulus; especially, the flow regime is turbulent and frictional pressure loss decreases as the pipe eccentricity increases. [DOI: 10.1115/1.4002243

Support Vector Regression and Computational Fluid Dynamics Modeling of Newtonian and Non-Newtonian Fluids in Annulus With Pipe Rotation

The estimation of the pressure losses inside annulus during pipe rotation is one of the main concerns in various engineering professions. Pipe rotation is a considerable parameter affecting pressure losses in annulus during drilling. In this study, pressure losses of Newtonian and non-Newtonian fluids flowing through concentric horizontal annulus are predicted using computational fluid dynamics (CFD) and support vector regression (SVR). SVR and CFD results are compared with experimental data obtained from literature. The comparisons show that CFD model could predict frictional pressure gradient with an average absolute percent error less than 3.48% for Newtonian fluids and 19.5% for non-Newtonian fluids. SVR could predict frictional pressure gradient with an average absolute percent error less than 5.09% for Newtonian fluids and 5.98% for non-Newtonian fluids

Hole Cleaning Performance of Light-Weight Drilling Fluids During Horizontal Underbalanced Drilling

Hole cleaning is a major consideration at both the design and application stages of a drilling operation. If the fluid velocity is lower than a critical value at horizontal or high inclinations, a stationary bed develops which may cause various problems, such as high drag, higher probability of stuck pipe and higher hydraulic requirements, etc., if not removed properly. Therefore, this becomes important and essential to identifying critical velocity. This study aims to estimate the critical fluid-flow velocity for preventing the development of a stationary bed using empirical correlations that can be used easily at the field. Also, a rough estimation of bed thickness is introduced if the flow velocity is lower than the critical velocity. For this purpose, extensive cuttings transport experiments with water, called the Cuttings Transport Flow Loop, were conducted by the Petroleum and Natural Gas Engineering Department at Middle East Technical University (METU) in order to determine various inclinations, flow rates and rate of penetrations. The inner pipe is subject to a sagging, therefore more realistic annulus representation is achieved. Observations showed that a stationary bed can be developed even when the inclination of the wellbore is down to 50 degrees. Results showed that the critical velocity could be estimated using the proposed correlations with reasonable accuracy when compared with the experimental results. Also, for flow velocities less than the critical values, the thickness of the stationary bed can be detected mostly within an error range of +/- 15%

Critical Fluid Velocities for Removing Cuttings Bed Inside Horizontal and Deviated Wells

This study aims to estimate the critical fluid flow velocity for preventing the development of a stationary bed using empirical correlations valid for horizontal and highly inclined wellbores that can be easily used at the field. For this purpose, experiments have been conducted at METU-PETE Cuttings Transport Flow Loop for various conditions. Observations showed that a stationary bed is developed when the fuid velocity is less than 6.0 ft/s, and a critical fluid velocity of 8.0 ft/s is required to establish a no-bed condition. Results showed that the critical velocity and the thickness of the stationary bed, if developed, could be estimated with a reasonable accuracy