"The hydraulic calculation requires the selection of a best fit model from some models used in petroleum industry. Especially, at low shear rate. This study is based on the data taken from ten wells to evaluate five models- Bingham plastic, Power Law, Casson, Herschel-Bulkley, and Robertson-Stiff for hydraulic optimization. In the course of optimizing, statistical method was used to evaluate all the data using linear regression and least square methods. Calculations were made to determine the rheological parameters, correlation coefficients and relative errors. Comparison was also made to the correlation coefficients and relative errors for selecting the best model for optimizing the hydraulics of specific drilling fluids. In order to verify the optimized results, the pressure losses both inside the drillpipe and the annulus and the Equivalent Circulating Density (ECD) were calculated by using these five models. Data obtained from Herschel-Bulkley model presented the most accurate results"--Leaf iii.
Recent studies highlighted the significant role of drilling fluid viscoelasticity in the assessment of frictional pressure loss, particle settling velocity, hole cleaning efficiency, and dynamic filtration loss control. Although the impact of drilling fluid viscoelasticity on the various functions of drilling fluids has been well recognized, the field implementation of these research findings have been hampered mainly because there has not been any standard field technique available for measuring the fluid viscoelastic properties. A comprehensive experimental investigation has, therefore, been conducted to develop a generalized model to determine the viscoelasticity of drilling fluids using standard field-testing equipment. The new field measurement-based methodology has then been used for developing new models and strategies that can be used for formulating optimum drilling fluid rheological properties for improving drilling fluid performance in two key applications areas; i-) Enhancing solids suspension ability, ii-) Reducing dynamic filtration loss. Ninety-three fluid formulations used in this study included field samples of oil-based drilling fluids as well as laboratory samples of water-based, invert emulsion and other oil-based fluids. Basic rheological characterizations of these fluids were done by using a funnel viscometer and a rotational viscometer. Elastic properties of the drilling fluids (quantified in terms of the energy required to cause an irreversible deformation in the fluid's structure called "energy dissipation") were obtained from oscillatory tests conducted by using a research grade rheometer with double gap concentric cylinder geometry. Using an empirical approach, a non-iterative model for quantifying drilling fluid elasticity was developed by correlating test results from a funnel iii viscometer and a rotational viscometer to energy required to cause an irreversible deformation of the fluid's elastic structure. Using the field measurement-based methodology for assessing the drilling fluid viscoelasticity , further experimental studies have been conducted to develop a generalized model for the field assessment of particle settling velocity in shear-thinning viscoelastic fluids by using the energy dissipation concept as an indicator of the fluid viscoelasticity. Ten different fluids were prepared in two groups based on their shear viscosity values. In each group, five fluids were having similar shear viscosity and variable elasticity values. Nineteen different spherical particles were used to conduct particle settling experiments with a density range from 2700 kg/m3 to 6000kg/m3 and a diameter range from 1mm to 4mm. Rheological characterizations of the fluids have been conducted by using funnel viscometer, API Rotational viscometer, controlled shear rate, and amplitude sweep test measurements. Fluid shear viscosity and elasticity have been identified as the most influential factors controlling filtration loss. However, past studies were mostly inconclusive regarding the individual effects of fluid shear viscosity vs elasticity, as it was very difficult to measure their effect independently. 24 water-based drilling fluids were prepared using various blends of three different molecular weight PHPA polymers. Two groups of fluids; one group having the same shear viscosity and variable elasticity and the other group having the same elasticity and variable shear viscosities, were developed. Additionally, 3 Xanthan Gum fluids were used as an example of iv visco-inelastic drill-in fluids commonly used for drilling long horizontal wellbore sections in the reservoir. Static filtration tests and core flooding experiments were conducted to measure the static filtration rate, pressure drop across the core at different flow rates, and formation damage induced by each fluid. By investigating the independent effects of viscoelasticity and shear viscosity on the fluid filtration loss characteristics, it was observed that: 1-) The static filtration rate can be more effectively controlled by altering fluid viscoelasticity as compared to the fluid shear viscosity. 2-) Both shear viscosity and viscoelasticity have a proportional relationship to the pressure drop associated with the core flow. However, the effect of viscoelasticity on the pressure drop is more pronounced. 3-) Increasing fluid viscoelasticity does not cause the formation damage as much as the shear viscosity. 4-)The viscoelasticity has been found to be the predominant rheological property that controls the solid-free drill-in fluids' filtration loss characteristics. The results have suggested that viscoelasticity can help develop non-invasive fluids by reducing static filtration rate, increasing pressure drop (effectively building internal cake), and minimizing formation damage.
The objectives of this book are (1) to serve as a reasonably comprehensive text on the subject of drilling hydraulics and (2) to provide the field geologist with a quick reference to drilling hydraulics calculations. Chapter 1 introduces the basic principles of fluid properties, and Chapter 2 presents the general principles of fluid hydraulics. Chapters 3 through 10 analyze specific hydraulic considerations of the drilling process, such as viscometric measurements, pressure losses, swab and surge pressures, cuttings transport and hydraulic optimization. References are presented at the end of each section. The units and nomenclature are consistent throughout the manual. Equations are given generally in consistent S.1. units; some common expressions are also given in oilfield units. Nomenclature is explained after every equation when necessary, and a comprehensive list of the nomenclature used is given in Appendix A. Units are listed in Appendix B. In Appendix C, all the important equations are given in both S.1. and oilfield units. Appendix D contains example hydraulics calculations. A glossary is included. THEORY AND APPLICATION OF DRILLING FLUID HYDRAULICS 1 INTRODUCTION To dri 11 a we 11 safely and succes sfull y depends upon a thorough unders tandi ng of drilling hydraulics principles. Thus, drilling hydraulics is a very impor tant subject with which all logging geologists should be familiar.
This study presents a simplified and accurate procedure for selecting the rheological model which best fits the rheological properties of a given non-Newtonian fluid and introduces five new approaches to correct for tool joint losses from expansion and contraction when hydraulics is calculated. The new approaches are enlargement and contraction (E & C), equivalent diameter (ED), two different (2IDs), enlargement and contraction plus equivalent diameter (E & C+ED), and enlargement and contraction plus two different IDs (E & C+2IDs). In addition to the Newtonian model, seven major non-Newtonian rheological models (Bingham plastic, Power law, API, Herschel-Bulkley, Unified, Robertson and Stiff, and Casson) provide alternatives for selecting the model that most accurately represents the shear-stress/shear-rate relationship for a given non-Newtonian fluid. The project assumes that the model which gives the lowest absolute average percent error (EAAP) between the measured and calculated shear stresses is the best one for a given non-Newtonian fluid. The results are of great importance in achieving correct results for pressure drop and hydraulics calculations and the results are that the API rheological model (RP 13D) provides, in general, the best prediction of rheological behavior for the mud samples considered (EAAP=1.51), followed by the Herschel-Bulkley, Robertson and Stiff, and Unified models. Results also show that corrections with E & C+2IDs and API hydraulics calculation give a good approximation to measured pump pressure with 9% of difference between measured and calculated data.
The rheological study of heavy crude oil is important in the field of petroleum engineering. The rheological properties of heavy oil (e.g., shear stress, shear rate, viscosity, etc.) depend on several factors including temperature, pressure, surface tension, diluent type and diluent composition, pH, shear stress and thermal histories, memory, and shear conditions during the analysis. The investigation of the rheology of heavy crude oil flow is a critical issue for both upstream and downstream operations. The objective of this study is to perform an investigation on the rheological properties of heavy crude oil to show the effect of shear rate, temperature, and pressure on the viscosity and the shear stress. The aim of this work was to broaden current knowledge of the rheological behavior and flow characterization of heavy crude oil. This paper takes a new look at the shear stress-strain relationship by considering the memory effect along with temperature effect on the shear rate. It is considered that the viscosity of the heavy crude oil is a function of pressure, temperature, and shear rate. As the heavy crude oil is considered as a Bingham fluid, Bingham model is employed here for the analysis. The experimental data from previous studies are used to complete the analysis. To develop the model, a modified Darcy's law that employs the effect of memory on the Bingham model is considered. The effect of temperature has been incorporated by the Arrhenius equation for the development of a new model to study the heavy crude oil rheological behaviors. The relationship between shear stress and viscosity has been shown at different fractional derivative order and time. The validation and the simulation of the model are performed by using the experimental and the field data from the literature. The numerical simulation of this model is conducted by using the MATLAB simulation software. From the sensitivity analysis, it is found that the temperature has the highest impact on the viscosity over the pressure and the shear rate. On the other hand, the pressure shows a strong effect on the shear stress-shear rate relationship over the temperature. In the model analysis, it is found that the fluid memory affects in the Bingham model due to nonlinear behavior of heavy crude oil. The shear stress increases with decreasing viscosity at different fractional derivative order and time. The change in shear stress is high at large fractional derivative. The range of fractional derivative order is from 0.2 to 0.8. When fractional derivative order,
The rheological properties of heavy oil and bitumen depend on factors such as temperature, pressure, diluent type and diluent composition, as well as sample shear and thermal histories and shear conditions during measurements. Each of these factors can affect the value of apparent viscosity significantly. Uncertainties in the available literature data arise when one or more of these factors have not been considered and have not been reported. Heavy oil and bitumen exhibit non-Newtonian rheological behaviors at lower temperatures. Methods for detecting and quantifying non-Newtonian behaviors are developed, presented and explored in this work using a well-characterized heavy crude oil. The methods and results presented for Maya crude oil provide a reliable database for rheological model development and evaluation, and a template for assessing the rheological behavior of other heavy crude oils. The thixotropic behavior of Maya crude oil was explored systematically using a stress-controlled rheometer. Thixotropy affects the efficiency and length scale of mixing during blending operations, and flow behaviors in pipes and pipelines following flow disruption where it affects the pressure required to reinitiate flow. Maya crude oil is shown to be a shear thinning fluid below 313 K. The thixotropic behaviors are explored using transient stress techniques (hysteresis loops, step-wise change in shear rate, start-up experiments). The magnitude of the thixotropy effect is larger at lower temperatures. Relationships are identified between rest times and other thixotropic parameters such as hysteresis loop area and stress decay in start-up experiments. Stress growth, which occurs as a result of a step-down in shear rate, is shown to correlate with temperature. The interrelation between rheological behavior of Maya crude oil and its phase behavior is discussed. The effect of pressure on the non-Newtonian rheological properties of Maya crude oil is also investigated over broad ranges of temperature from (258 to 333) K and at pressures up to 150 bar. At fixed temperature, the magnitude of the non-Newtonian behaviors of Maya crude oil appears to increase with increasing the pressure and shear thinning is shown to persist to higher pressures below 313 K. Boundaries of the non-Newtonian region with respect to temperature, pressure and viscosity are identified and discussed. The thixotropic behavior of Maya crude oil is also shown to persist at higher pressure and the recovery of the moduli at rest appears to be faster at elevated pressures than at atmospheric pressure. Understanding the rheological properties of mixtures of heavy oil or bitumen and diluents, specifically at low temperatures, is key in designing different processes employed in production or transportation of these resources reliably and efficiently. The effect of diluents (n-heptane, toluene and toluene + butanone (50/50 vol. %)) on the non-Newtonian behavior of Maya crude oil including shear thinning and thixotropy at temperatures from (258 to 333) K are discussed. Toluene + butanone (50/50 vol.%) addition to Maya crude oil induces the greatest reduction in shear thinning behavior irrespective of temperature. Thixotropic properties of mixtures of Maya crude oil and diluent were studied through start-up experiments. It was shown that toluene + butanone (50/50 vol.%) is the best diluent in moderating the thixotropic effect, while n-heptane showed the most pronounced thixotropic effect. It was shown that toluene + butanone (50/50 vol. %) is more promising in decreasing oil viscosity in comparison to two other diluents tested. Less of this diluent is required to decrease the viscosity to a certain value, which confirms its potential application to be used in the industry as a diluent.
