Viscosity Marsh funnel

The measurement of the rheology of drilling fluid samples at the rig site is made by two methods. The first method uses the Marsh funnel (Figure 6) to measure the time taken to empty a given volume (one U.S. quart or 946 mL) of drilling fluid. The time taken to empty the funnel is termed the Marsh funnel viscosity and typically ranges from 30-80 s ... 

Likewise the use of the Marsh funnel viscosity to predict the best suspending fluid would not have led to selecting the best fluid. The Marsh funnel viscosity of the HEC fluid was 84 seconds as compared to 53 seconds for the xanthan polymer solution. 

Historically, viscosity measurements have been the single most important method to characterize fluids in petroleum-producing applications. Whereas the ability to measure a fluid s resistance to flow has been available in the laboratory for a long time, a need to measure the fluid properties at the well site has prompted the development of more portable and less sophisticated viscosity-measuring devices [1395]. These instruments must be durable and simple enough to be used by persons with a wide range of technical skills. As a result, the Marsh funnel and the Fann concentric cylinder, both variable-speed viscometers, have found wide use. In some instances, the Brookfield viscometer has also been used. 

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