Optimization of Drilling Fluid Rheological Properties for Improved Cuttings Transport and Dynamic Filtration Loss Control Performance: A Comparative Study of the Fluid Viscoelasticity versus the Shear Viscosity Effects
Creators: Chen,Hongbo
Publisher: name: University of Alberta Library
Year: 2022

<p>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.<br>
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.<br>
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<br>
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viscometer and a rotational viscometer to energy required to cause an irreversible deformation of the fluid’s elastic structure.<br>
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.<br>
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.<br>
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.<br>
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<br>
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visco-inelastic drill-in fluids commonly used for drilling long horizontal wellbore sections in the reservoir.<br>
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.<br>
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.</p>