Variations of mud flowmeter technology can likewise measure drilling rig streams such as mud blending, mud shipment and pumping operations to improve mud formulation, ensure accurate custody transfer and assess equipment health, respectively. These measurements can provide significant value by enabling drilling rigs to operate with fewer upsets and less downtime, while increasing safety and reducing the number and severity of expensive and time-consuming repairs.

For example, mud with incorrect density pumped into the well can be detected quickly to avoid potentially spending multiple non-productive days flushing the well. Reducing downtime by only 1% would increase drilling rig availability by almost four days per year. Drilling rig rentals are approximately USD $250,000 per day onshore and USD $750,000 per day offshore, so the economic value of these four additional drilling days is approximately USD $1,000,000 and USD $3,000,000, respectively. Therefore, investing (say) USD $500,000 for these flowmeters would result in simple paybacks of 6 and 2 months, respectively, suggesting that their purchase and installation should be aggressively pursued.

Excerpted from Measuring Difficult Flow Streams and More Accurate Flow Control Can Improve Oil and Gas Well Profitability in Processing magazine.

Looking back, this application and installation had multiple problems, but you might not think that to be the case if you followed the issues in sequence. First, the flowmeter was reported to be measuring low. Apparently nothing else was wrong, but after the flow measurement was corrected, the flow measurement repeatedly dropped out. My client initially observed both symptoms, but he chose to initially report only the measurement error as a problem.

The second problem (drop out) was not mentioned until the first problem was resolved. Had my client mentioned the second problem in conjunction with the first problem, he would not have had to expend as much time, effort and resources to have a technician visit the plant to obtain information that was relayed to the representative, and afterwards, to the factory. Similarly, the factory would not have had to diagnose the first problem only to be confronted with a second problem that rendered the flowmeter marginally operational in this application.

Situations where more than one problem exists are typically more difficult to identify and resolve than their single-problem counterparts. This can be especially frustrating when one of the problems turns out to be fatal to the application such that the instrument will not work. Be sure to question people completely and train them to share all of their observations with you --- so you can better help them.

 This article originally appeared in Flow Control magazine.

Viscosity is the ability of a fluid to flow over itself. Newtonian fluids exhibit the same viscosity without regard for how the fluid is stressed. Answer C is correct.

Additional Complicating Factors

Discussions about viscosity can quickly become complicated --- even after disregarding the relatively large number of viscosity units in common use. The viscosity of some common fluids can vary when the fluid is stressed.

Surely you have tried to remove ketchup from its bottle. You may have noticed that mildly shaking the bottle will not cause the ketchup to flow because the ketchup exhibits a relatively high viscosity under this condition. More vigorous shaking will start flow and the viscosity appears to drop. Once started, the ketchup flow can increase even more as its viscosity drops further. Put differently, did you ever try to put ketchup on a hamburger by shaking the ketchup bottle increasingly more intensely --- only to suddenly find a big blob of ketchup on the hamburger? Such can be consequences of viscosity variations associated with fluids that are not Newtonian.

Other liquids can exhibit the opposite effect, that is, more vigorous action causes the viscosity to increase and reduce flow. This can occur in some slurry flows where increasing the speed of a pump can actually reduce the flow rate because the increasing viscosity of the slurry increases the pressure drop in the discharge piping thereby reducing the slurry flow.

As mentioned above --- discussions about viscosity can quickly become complicated.

This article originally appeared in Flow Control magazine.