Can we improve drilling fluid rheology predictions by rotational viscometer?

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The success in the drilling and construction operations of an oil well is in a correct formulation of the drilling fluid, since with a correct formulation of the drilling fluid we will be able to make a correct follow-up of its rheological properties.

The fann viscometer is an instrument to measure the viscosity of the drilling fluid, so it is convenient to be able to study all the possible improvements that can be obtained in the measurement of the rheological parameters of the drilling fluid based on the use of the fann viscometer.

The first important thing to improve the predictions of drilling fluid rheology is to be able to establish some comparative elements of other viscosity measurements with the viscosity measurement using the fann viscometer, for this we can perform gel strength tests, for this we can use in the laboratory of drilling fluids classic measurement devices such as sliding the drilling fluid on the wall, evaluate the possibility of the emergence of secondary flows and thus to realize the performance of the drilling fluid when it is at rest.

Being able to simulate the behavior of the drilling fluid in a laboratory at reservoir conditions can also give us an idea of the relationship between the pressure drop and the flow rate of the drilling fluid in the well while we are drilling. When we perform such a simulation process what we are looking for is to know the influence that viscosity and other rheological properties have on the design of pipes and the correct sizing in the choice of the size of the mud pumps. We cannot discard in this simulation process the possible benefit that we can have if we rely on the use of the American Petroleum Institute (API) equations and curve fitting as possible adjustments in the different viscosity values obtained.

After following the experimental studies of some tests and simulations in laboratories, it is possible to interpret indicative results that the use of equations of the American Petroleum Institute can be positively influential in the effectiveness of the process of drilling wells using drilling fluids to which the respective viscosity and rheological properties analysis are made to obtain a correct selection of viscosity values according to the correct operation of the mud pumps in relation to their arrangement and size.

We must take into account that if we evaluate the gel strength capacity of a drilling fluid based on the values that we can have if we measure it in a fann viscometer, most likely they will be very different from those measured with other instruments, so it is recommended to make any relevant adjustment in the fann viscometer in relation to its geometry and structure, with this what we will achieve is that no sliding effects of the drilling fluid occur at very low shear rates, which in the end are the low shear rates that prioritize these differences in viscosity measurements.

Conclusión

It is important that in this process of comparison between the results obtained in the measurements of a fann viscometer versus other types of measurements can extract data that serve to provide recommendations that are consistent with the demands of all the physical properties of the drilling fluid, because if the comparisons in relation to viscosity measurements is done correctly we can get a better accuracy in the results of rheology calculations in the hydraulic design of the well drilling.

References

Drilling Fluids Rheology: Basics and Definitions

Drilling Fluid Rheology for Drilling Engineers