Papers by Evren Ozbayoglu
Journal of Petroleum Science and Engineering, 2018
The low density enables lightweight cement to be an ideal candidate for petroleum drilling in dep... more The low density enables lightweight cement to be an ideal candidate for petroleum drilling in depleted formations. Lightweight cement is able to tolerate more deformation due to its high strain capacity. The major challenge, however, is its relatively low strength properties. Carbon nanotubes (CNTs) have been used in multiple industries to improve the strength, strain capacity, and durability of materials. In this study, the effect of CNTs on the mechanical properties of lightweight cement under triaxial loading conditions was analyzed. Two different lightweight cement systems, foam and microsphere cements, mixed with multi-walled carbon nanotubes at the concentration of 0.5%wt. were investigated and compared to conventional cement. Young's modulus, compressive strength, brittleness and strain capacity were measured under elevated confining pressures. Permeability and splitting tensile strength were calculated based on test
Fluid flow and heat transfer modeling in the event of lost circulation and its application in locating loss zones
Journal of Petroleum Science and Engineering, 2017
Abstract Lost circulation is one of the most persistent and costly drilling problems that drillin... more Abstract Lost circulation is one of the most persistent and costly drilling problems that drilling engineers have been struggling with for decades. The pinpointing of the zones of loss allows the treatments to be applied directly to the points of loss rather than to the entire open hole. This paper presents an approach to predict the location of single loss zone in a vertical well by interpreting the transient mud circulating temperature profiles altered by mud loss. The fluid flow and heat transfer numerical model in estimating the transient mud circulating temperature profiles during a lost circulation event was developed. The temperature profile in both the flow conduits (drillpipe and annulus) were modeled using mass and energy balances. The flow rate of drilling mud decreases in the annulus above the loss zone as part of the fluids lost into the fractures, which in turn alters the heat transmission status between the drillpipe, annulus, and near-wellbore formation. The wellbore is divided into two sections, which accounts for single loss zone. Case studies were performed and numerical solution results were presented and analyzed. According to the results, alterations induced by mud loss include: 1) Declines in both annular mud temperature and drillpipe mud temperature over time, and 2) Discontinuity in the first order derivative of annular mud temperature with respect to depth at the location of loss. By matching the simulated results with the distributed temperature measurements at different time stamps, the depth of the loss zone can be identified.
Journal of Energy and Power Engineering, 2016
Failure to manage and minimize lost circulation can greatly increase the cost of drilling and the... more Failure to manage and minimize lost circulation can greatly increase the cost of drilling and the risk of well abandonment. Many lost circulation remedial procedures are not working as planned because the locations of loss zones are incorrectly estimated. The lack of this critical piece of information prevents treatments from being applied directly to the points of losses and, thus, resulting in low efficiency and extended NPT (non-productive time). This paper presents an integrated method for identifying the locations of loss zones with continuous temperature measurement data enabled by drilling microchip technology. A transient thermal model in predicting the temperature profiles in the wellbore and formation during mud loss is developed as a forward calculation procedure of the loss zone mapping method. For a deep well with moderate to severe loss, there are significant changes in the mud circulating temperature profiles as mud loss persists. Certain characteristics of wellbore thermal behavior are evaluated and identified as good indicators of loss zones. Case studies are conducted to demonstrate the practical applications of the method in both onshore and offshore drilling applications. The results from these case studies are important in setting cement plugs, applying expandable tubular systems, and spotting LCM (lost circulation material) pills. Additional uses of this method include identifying highly permeable zones for reservoir or formation evaluation purposes. This method can be used as a routine monitoring process performed regularly without any interference of the drilling operations at the time.
Drilling Fluid Density and Hydraulic Drag Reduction With Glass Bubble Additives
Journal of Energy Resources Technology, 2017
This study concentrates on the use of materials known as hollow glass spheres, also known as glas... more This study concentrates on the use of materials known as hollow glass spheres, also known as glass bubbles, to reduce the drilling fluid density below the base fluid density without introducing a compressible phase to the wellbore. Four types of lightweight glass spheres with different physical properties were tested for their impact on rheological behavior, density reduction effect, survival ratio at elevated pressures, and hydraulic drag reduction effect when mixed with water-based fluids. A Fann75 high pressure high temperature (HPHT) viscometer and a flow loop were used for the experiments. Results show that glass spheres successfully reduce the density of the base drilling fluid while maintaining an average of 0.93 survival ratio, the rheological behavior of the tested fluids at elevated concentrations of glass bubbles is similar to the rheological behavior of conventional drilling fluids and hydraulic drag reduction is present up to certain concentrations. All results were int...
Mixing of Cement Slurries During Cement Plug Setting
Day 2 Thu, September 15, 2016, 2016
Cement plugs are used for various reasons in wellbores, including control of lost circulation zon... more Cement plugs are used for various reasons in wellbores, including control of lost circulation zones, initiation of deviation or side tracking, wellbore abandonment, and more. Unfortunately, one of the most questionable processes during the drilling and completion stage of a wellbore is the quality of the cementing job. As in conventional cementing operations, cement plug setting requires an efficient fluid displacement process to be considered "successful." Due to the nature of the operation, i.e., displacing one fluid with another inside a tubular, mixing of the fluids during this process is inevitable, because the fluids are in contact via a contacting interface. The stability of this interface depends on many parameters, such as flow rate, pipe size, inclination, displacing and displaced fluid rheological properties, as well as densities, interfacial tension between the fluids, etc. Therefore, an optimization process is required to minimize the mixing and thus to maximi...
Two-Phase Fluid Flow Through Fully Eccentric Horizontal Annuli: A Mechanistic Approach
Proceedings of SPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition, 2007
Copyright 2007, Society of Petroleum Engineers This paper was prepared for presentation at the 20... more Copyright 2007, Society of Petroleum Engineers This paper was prepared for presentation at the 2007 SPE/ICoTA Coiled Tubing and Well Intervention Conference and Exhibition held in The Woodlands, Texas, USA, 2021 March 2007. This paper was selected for ...
A discussion about horizontal foam flow behavior in pipes and annular geometry under elevated pre... more A discussion about horizontal foam flow behavior in pipes and annular geometry under elevated pressures and temperatures is presented. The study is empirically based and covers the effects of foam quality, foam texture, pressure, temperature and geometry of the conduit on the rheological response of foams.
All Days, 2006
Determination of pressure drop at the bit is one of the major concerns for establishing proper hy... more Determination of pressure drop at the bit is one of the major concerns for establishing proper hydraulic design. Little has been known about pressure drop estimation at the bit for single phase muds, and even less is known about gasified fluids. The aim of this study is to fulfill this gap in the literature. Although there are numerous studies on this subject available in the literature, they are either valid for high gas flow rates or developed using very strong assumptions. The proposed theory, which is valid for both sonic (critical) and subsonic (sub-critical) regimes, is based on the solution of the general energy equation for compressible fluid flow. Unlike the existing models in the literature, the proposed model takes the change in kinetic energy, compressibility factor, and internal energy terms into consideration. Moreover, the model uses "a mixture sound velocity" approach for determination of the sonic boundary of the fluid. Based on the proposed model, a compu...
SPE Journal, 2012
Summary This study aims to investigate the hole-cleaning process during the flow of a drilling fl... more Summary This study aims to investigate the hole-cleaning process during the flow of a drilling fluid consisting of a gas and a liquid phase through a horizontal annulus. Experiments have been conducted using the Middle East Technical University (METU) multiphase flow loop under a wide range of air- and water-flow rates while introducing cuttings into the annulus for different amounts. Data have been collected for steady-state conditions (i.e., liquid, gas, and cuttings injection rates are stabilized). Collected data include flow rates of liquid and gas phases, frictional pressure drop inside the test section, local pressures at different locations in the flow loop, and high-speed digital images for identification of solid, liquid, and gas distribution inside the wellbore. Digital imageprocessing techniques are applied on the recorded images for volumetric phase distribution inside the test section, which are in dynamic condition. The effects of liquid and gas phases are investigated...
Friction Factor Determination for Horizontal Two-Phase Flow Through Fully Eccentric Annuli
Petroleum Science and Technology, 2009
In this study, empirical friction factor correlations were developed for two-phase stratified- an... more In this study, empirical friction factor correlations were developed for two-phase stratified- and intermittent-flow patterns through horizontal fully eccentric annuli. Two-phase flow hydraulics were investigated, and a flow pattern prediction model is proposed. The friction factor correlations were validated using experimental data collected at the multiphase flow loop METU-PETE-CTMFL. Two different geometrical configurations were used during experiments—that is, 0.1143 m inner diameter (ID) casing, 0.0571 m outer diameter (OD) drillpipe; and 0.0932 m ID casing, 0.0488 m OD drillpipe. The eccentric annuli has been represented by representative diameter dr. A new mixture Reynolds number based on liquid holdup is proposed for friction factor determination.
Critical Fluid Velocities for Removing Cuttings Bed Inside Horizontal and Deviated Wells
Petroleum Science and Technology, 2010
This study aims to estimate the critical fluid flow velocity for preventing the development of a ... more 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.
Viscosity and Density Sweeps in Directional Wells
As explorations advance and drilling techniques become more innovative, complex and challenging t... more As explorations advance and drilling techniques become more innovative, complex and challenging trajectories arise. In consequence, cuttings transport has continued to be a subject of interest because, if the drilled cuttings cannot be removed from the wellbore, drilling cannot proceed for long. Therefore, efficient cleaning of highly inclined and horizontal wellbores is still among the most important problems to solve, because these types of wells require specialized fluid formulations and/or specific hole cleaning techniques. There are numerous studies and methods that focus in cuttings transportation in highly inclined and horizontal wells. One of them is the use of viscosity and density sweeps. Sweep pills have been used in the drilling industry as a tool to improve hole cleaning. This report presents the analysis of the performance of different sweeps pills working independently and in tandem in polymeric, oil and synthetic based systems and the comparison between them. The main objective of this project is to provide experimental evidence on which types of fluids perform better under certain conditions by studying the effect of viscosity and density in the bed erosion process in highly inclined and horizontal wells. In order to achieve that, several fluid formulations were tested at different inclination angles (90, 75, 60 degrees) in the Small Indoor Flow Loop property of The University of Tulsa’s Drilling Research Projects. The results of the tests are presented in terms of volume of drilled cuttings removed from the test section and measured differential pressures. All the tests were conducted under atmospheric pressure and ambient temperature. Moreover, a 2-Layer model is used for estimating the erosion performance of sweeps for design purposes, and the model estimations are compared with experimental results. From the experiments, it was identified that polymeric, oil and synthetic based muds with similar density and rheological properties eroded and transported the drilled cuttings similarly under similar test conditions. Furthermore, pumping the sweep pills in tandem demonstrated higher cuttings transport efficiency when compared with the sweep pills applied independently.
A Fast Graphic Approach To Estimate Hole Cleaning for Directional Drilling
SPE Drilling & Completion
Summary In this paper, a set of charts is developed to allow drilling engineers to quickly estima... more Summary In this paper, a set of charts is developed to allow drilling engineers to quickly estimate the cuttings volumetric concentration in the wellbore. The most-important parameters for hole cleaning are divided into several ranges on the basis of their sensitivity to cuttings concentration in the wellbore. A series of charts is obtained by running a hole-cleaning simulator, which is based on a large number of experimental and modeling studies of cuttings transport. The difference between the charts’ prediction results and experimental data is within 20%. Drilling engineers can quickly estimate the cuttings volumetric concentration by looking up the charts and conducting very-simple calculations.
Journal of Petroleum Exploration and Production Technology, 2016
Slurry transport has become a subject of interest in several industries, including oil and gas. T... more Slurry transport has become a subject of interest in several industries, including oil and gas. The importance of slurry/solid transport in the oil and gas industry is evident in areas of cuttings transport, sand transport and, lately, hydrates. There is therefore a great need to develop instrumentation capable of characterizing fluids with high solid content. Presence of solids in fluids makes the rheological characterization of these systems difficult. This is because available rheometers are designed with a narrow gap and cannot prevent solids from settling. The main aim of this paper is to present a step-by-step procedure of converting torque and shaft speed into viscosity information by applying the Couette analogy, equivalent diameter and inverse line concepts. The use of traditional impeller geometries such as cone and plate may be challenging due to their narrow gap and inability to prevent settling. Therefore, the use of nonconventional impeller geometry is imperative when dealing with settling slurries and suspensions. The most challenging task using complex geometry impeller is data interpretation especially when dealing with complex rheology fluids. In this work, an autoclave is transformed into a mixer-type viscometer by modifying its mixing, cooling and data acquisition systems. Mathematical models relating the measured torque to shear stress and the measured shaft speed to shear rate were developed and expressed in terms of the equivalent diameter. The shear rate and shear stress constants were expressed in terms of equivalent diameter and measureable parameters such as impeller speed and torque. The mixer-type viscometer was calibrated using four Newtonian and four Power-Law fluids to determine the rheological constants (equivalent diameter, shear rate and shear stress constants). The concept of inverse line was used to identify the laminar flow regime. The calibrated instrument was used to characterize two Power-Law fluids. This procedure can be extended to any rheological model. Methods developed in this work can be used to characterize fluids with high solid content. This is particularly important when dealing with complex rheology slurries such as those encountered in food processing, oil and gas and pharmaceuticals.
Journal of Petroleum Exploration and Production Technology, 2016
Transportation of solids in form of slurries has become one of the most important unit operations... more Transportation of solids in form of slurries has become one of the most important unit operations in industries across several disciplines. In fact, the need is more pronounced in industries that are very important for human survival such as food processing, pharmaceuticals and energy (coal, oil and gas). A lot of work has been done in the past 30 years in understanding the factors affecting the deposition velocity of solids in slurries. Experimental observation and theoretical predictions pointed to mixture velocity and solid/fluid properties especially rheology of the resulting slurry to be the most important factors that dramatically affect particle motion and patterning. This paper presents a critical deposition velocity model and a ''stability flow map'' for complex rheology slurries. The critical deposition model utilizes a more robust generalized two-parameter rheology model to account for any given slurry rheology. The ''stability flow map'' demarcates the different flow patterns that may be observed at different mixture velocities and rheologies. On this map, the homogeneous slurries are predicted at low rheology and high mixture velocity, whereas heterogeneous slurries (with a concentration gradient) predicted at high rheology (yield stress effects). Sensitivity analysis was conducted on critical Reynolds number, particle density, carrier fluid density, generalized flow behavior index and pipe diameter. It was observed that increase in shear thinning behavior, particle density, pipe diameter and particle diameter led to a decrease in the laminar region and an increased unstable region. The model showed good performance when tested on glass and stainless steel beads test data available in open literature. Preliminary simulation with this map may help engineers select flowline size and carrier fluid rheology for a given type of solid particle. Keywords Rheology Á Particulate flow Á Slurry Á Flow regime Á Flow assurance Á Stability map List of symbols 1-C s Liquid volume fraction (-) C s Solid particle volume fraction (-) D Pipe inner diameter (m) d Particle diameter (micron) g Gravity (ms-2) K Viscosity consistency coefficient (mPa s N) n Flow behavior index/power law exponent (-) N Generalized flow behavior index (-) Re G Generalized Reynolds number (-) Re G,t Generalized transitional Reynolds number (-) S Ratio of solid density to carrier fluid density, q s =q f (-) V Velocity (ms-1) V c Critical deposition velocity (ms-1) V l Laminar deposition velocity (ms-1) V t Transitional deposition velocity (ms-1) x c Ratio of yield stress to wall shear stress, s y /s w (-) a Ratio of wall shear stress to surficial particle shear stress, s w /s p (-) g m Viscosity function (mPa s N) l Viscosity (mPa s) l B Plastic viscosity (mPa s) l m Mixture fluid viscosity (mPa s) l w Carrier fluid viscosity (mPa s) q Density (kg m-3
Experimental Study and Modelling of Barite Sag in Annular Flow
Journal of Canadian Petroleum Technology, 2014
The phenomenon of settlement of weighting-material particles in drilling fluid is known as barite... more The phenomenon of settlement of weighting-material particles in drilling fluid is known as barite sag, which can lead to a number of drilling problems including lost circulation, well-control difficulties, poor cementing operation, and stuck pipe. This study investigates barite sag, both experimentally and numerically, in the annulus under flow conditions. Settlement of the weighting materials is generally called barite sag because barite is the most popular weight material used in drilling industry. The experimental part of the study has been conducted using a flow loop with 35-ft-long annulus test section to investigate the effects of fluid velocity in annulus, annulus eccentricity, pipe rotation, and inclination angle on barite sag. Density of the flowing fluid is measured continuously using Coriolis densitometers at the inlet and outlet of the annular test section. The simulation part of this study is based on a proposed particle- tracking method called “particle-elimination tec...
Drill Bit Pressure Drop During Foam Drilling Operations
Journal of Canadian Petroleum Technology, 2008
Foam is one of the most frequently used drilling fluids for underbalanced drilling operations. Th... more Foam is one of the most frequently used drilling fluids for underbalanced drilling operations. This paper introduces a more accurate model than the existing models for estimating the pressure drop of foam flowing through the drill bit. The major difference between the proposed and existing models is that the proposed model includes the effect of foam expansion and velocity change as a function of pressure. It has been observed that pressure drop increases significantly as the upstream pressure and foam average velocity increases. For the same flow conditions, pressure drop decreases as the foam quality increases, and as the upstream pressure increases, pressure drop also increases. These events cannot be detected by existing models. In some cases, the pressure drop at the bit can be 10 times greater than the pressure drop predicted by existing models. Introduction Foam has been used as a drilling fluid in many drilling operations; especially in underbalanced drilling applications. In a number of cases, drilling with foam has shown to provide significant benefits, including increased productivity (by reducing formation damage), increased drilling rate, reduced operational difficulties associated with drilling in low pressure reservoirs (e.g. lost-circulation and differentially stuck pipe) and improved formation evaluation while drilling. Foams consist of a continuous liquid phase, forming a stable cellular structure that surrounds and entraps a gas phase. Special chemicals, called surfactants, are used to capture the gas phase; at least for a desired period of time. Foams are considered to be dry or wet, depending on the gas content. Wet foams have spherical bubbles with large amounts of liquid between the bubbles. Dry foam bubbles are polyhedral in shape, with definite contact between the bubbles. In between these two extremes, geometrical figures having both curved and flat faces can exist. Foams are thermodynamically unstable systems because they always contain more than a minimal amount of gas solution interface(1). This interface represents surface free energy, the amount of which can be estimated from knowledge of the surface tension and the interfacial area of the foam. Wherever a foam membrane breaks and the liquid coalesces, there is a decrease in surface free energy. Thus, the decomposition of foam into its constituent phase is a spontaneous process. Since the solution phase is always denser than the gaseous phase, there is a strong tendency for the liquid to separate or drain from the main body of foam unless it is circulated or agitated in some way. Foams can have extremely high viscosity. In all instances, their viscosity is greater than either the liquid or the gas that they contain(2). At the same time, their densities are much lower than the density of water. They are stable at high temperatures and pressures. So, by using foam as a drilling fluid, its high viscosity allows efficient cuttings transport and its low density allows underbalanced conditions to be established; thereby minimizing formation damage. Foams are also preferred when water influx is a problem because they can handle large amounts of water.
Optimization of Liquid and Gas Flow Rates for Aerated Drilling Fluids Considering Hole Cleaning for Vertical and Low Inclination Wells
Journal of Canadian Petroleum Technology, 2010
Summary Underbalanced drilling (UBD) is one of the most widely used technologies preferred in dep... more Summary Underbalanced drilling (UBD) is one of the most widely used technologies preferred in depleted and/or low-pressured formations. In order to achieve underbalanced conditions, drilling fluids are usually gasified. Major drilling fluids preferred during UBD are pure gas, gas-liquid mixtures, and foams. This study is focused on gas-liquid mixtures. As the gas is introduced, the behaviour of the drilling fluid becomes hard to explain for many reasons. First of all, gas is compressible and physical properties of gas are very sensitive to changes in pressure and temperature. Second, a multiphase flow phenomenon arises. When there is multiphase flow, flow patterns should be considered. It is known that there is a difficulty to predict hydraulic behaviour of gas-liquid mixtures owing to this flow pattern dependence. During a drilling operation, one of the parameters that should be considered is hole cleaning. Hole cleaning is a challenging task even for a single-phase drilling fluid. Moreover, there is still a lack of information about how the cuttings are transported when gas-liquid mixtures are used as drilling fluids. Flow-rate optimization during UBD operations for liquid and gas phases are usually conducted based on formation pressures only. However, considering only this criterion as the optimization objective is misleading and may cause serious problems during the drilling operation. In this study, gas and liquid flow rates during UBD operations are conducted not only based on formation pressures, but also based on effective hole cleaning. It is assumed that liquid phase is the major contributor for cuttings transport, and gas phase is only influencing the bottomhole pressure. A mechanistic model is introduced for estimating the hydraulic behaviour of gas-liquid mixture drilling fluids under different flow patterns. Based on the bottomhole pressure and effective hole cleaning point of view, an algorithm is proposed for estimation of the optimum required flow rates for liquid and gas phases based on the introduced mechanistic model. Also, the model predicts the required backpressure that has to be applied.
Empirical Correlations for Estimating Filtrate Volume of Water Based Drilling Fluids
Http Dx Doi Org 10 1081 Lft 200031037, Feb 14, 2007
... Evren Ozbayoglu a , Cagri Gunes a , Esat C. Apak a , Mustafa Versan Kok a * & A. Gurk... more ... Evren Ozbayoglu a , Cagri Gunes a , Esat C. Apak a , Mustafa Versan Kok a * & A. Gurkan Iscan a pages 423-436. ... HP&HT filtrate tests match with the bottom hole conditions and give better results (Kassim and Sharma, 20026. Kassim , AR , Sharma , M. SPE 73769 ( 2002 ). ...
Experimental Investigations of the Effect of the Pore Pressure on the MSE and Drilling Strength of a PDC Bit
SPE Western North American and Rocky Mountain Joint Meeting, 2014
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Papers by Evren Ozbayoglu