Measuring Lubricity
In most drilling fluid labs, lubricity is measured by converting the current applied to a motor rotating against a stationary object to a torque value. Untreated and treated fluids are compared for a relative torque reduction.
The most common measurement device is the EP lubricity meter where a block is pressed against a rotating ring assembly. The assembly is immersed in fluid for the reading. An example of output data is shown to the right. In this example, various concentrations of various products are compared to show both performance in overall torque reduction and the optimal concentration for best performance.
Another measurement device, the lubricity evaluation monitor (LEM) rotates a spindle against a sample of casing or sandstone inside a cell where drilling fluid is circulated.
There are a number of other devices, but as they become more complex to mimic downhole conditions the tests become increasingly expensive. No matter the testing methods, laboratory data must ultimately be evaluated in the field by monitoring actual torque and drag reduction versus an untreated fluid.
