University of New South Wales
School of Petroleum Engineering
Experiment No. 2: Control and measurement of rheological properties of drilling mud
Course name: Well Drilling Equipment and Operations (PTRL3015) Date of lab: 18/04/2014
Date of submission: 09/05/2014
Group details: Odd week, Friday lab
Table of Contents
This laboratory experiment has as objective to introduce to the rheological properties of drilling fluid, including plastic viscosity, apparent viscosity, Gel strength(GS), exponent of ffow behaviour of power fluid (n), consistency index of power law fluid(k) and yield point (YP). It is also an objective of this experiment to measure the rheological properties using an equipment called FANN viscometer and to control the mud properties. To achieve these objectives, devices such as mud balance, FANN viscometer, mud mixer and electronic mass scale are used. Four groups developed four different muds: mud 1 (water + bentonite), mud 2 (water+ bentonite + barite), mud 3(water+ bentonite + barite + polymer), mud 4 (water + bentonite + barite + polymer + CaCl2) in order to compare the rheological properties of each. It was observed that the density of mud 2 increased due to the adding of barite and there was an increase in the density of the muds, because of the adding of bentonite, polymer and CaCl2. All the mud behave as a Bingham plastic fluid. To conclude, with was observed that the components used to develop a mud define the rheological properties of the mud. Therefore, It is important to measure the ideal components to mix in order to get the best cost / benefit ratio for the drilling of a well.
It is possible to change rheological properties of mud, mixing different substances. In this way, a mud with certain properties can optimize its function. Therefore, four mud with different components were prepared for four groups in the laboratory in order to compare and achieve the following objectives: Understand the rheological properties of drilling fluid,
Measurement of rheological properties using FANN viscometer, such as plastic viscosity, apparent viscosity, Gel strength(GS), exponent of ffow behaviour of power fluid (n), consistency index of power law fluid(k) and yield point (YP). Control mud properties
Rheology of drilling fluids
Rheology is the branch of physics that studies the viscosity, plasticity, elasticity and flow of matter caused by friction of the fluid, ie, a study of changes in the shape and flow of a material, comprising all these variants. Viscosity is the most acknowledge rheological property and is characterized by measuring the flow resistance, which matter is caused by internal friction that occurs in the material, where a fluid layer has a certain resistance when moving over another. Moreover, The type of the fluid, including Newtonian fluids, Bingham plastic, Power law and Herschel-Bulkley, can be defined by the relationship between shear rate and shear stress, which is measured in the FANN viscometer. Therefore, the viscosity of fluid can defined as:
Where F=force required to maintain the velocity gradient dv / dx, A= area between adjacent planes of a fluid. In addition, viscosity is the only rheological property that characterizes the Newtonian fluids, since the relationship between shear rate and stress in a Newtonian fluid is linear (viscosity is the slope of this line). The viscosity of a drilling fluid, which is a complex mixture of clay, polymer and other substances, depends on the friction between solids, between the solid and liquid phases, between liquid phases and also depends on the degree of interparticle force, caused by the clay in the mud. Because of this, the relationship between shear rate and stress is non-linear for a drilling fluid and consequently, the viscosity is shear dependant. A typical clay suspension is a Binghan plastic...
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