During drilling operations, it is of vital importance to have accurate and reliable volume control, with as fast as possible detection of flow abnormalities. The earlier a flow abnormality is detected; the faster actions can be taken to minimize the consequence and cost of a potential well control incident. Accurate and reliable measurements of the inflow of mud and return flow is key to improvements in volume control and early kick detection. Uncertainty and time delay in these measurements may lead to well control incidents such as uncontrolled fracturing, collapse of wells, influx and, in worst case, external spill of oil and gas to the surface.

Existing inline traditional meters experience challenges due to clogging of measurement ports, mechanical erosion or damages on gaskets. Such being caused by the nature of mud consisting of a mixture of heavy materials and cuttings from the formation. Most of them are also not able to give quantified measurements, relying on human interpretation of trends in the data.

Using Clamp-on flow meters for mud measurement would significantly reduce cost, risk and maintenance work if it could generate accurate and reliable measurements. However, due to its nature, drilling mud is a difficult medium to measure and several other technologies have come short trying to do so, including previous ultrasonic measurement techniques.  

This non-invasive ultrasound transmission concept, enables off-center beam transmission, forming the functionality of a multi-beam inline acoustic flow meter. The patented technology achieves this through disruptive acoustic guided wave transmission technology where the pipe wall is used as an advanced transmitting gateway between sensors, and helical shaped transducers enables measurements off-center signal transmission creating shorter paths than traditional clamp-on Meters in addition to traditional axial signal transmission. Combining these features enables measurements also through mud.

This paper will present the theory behind the technology, technology advantages and potential, as well as flow test results from mud flow loop at a Mud loop testing facility in Norway performed in September 2018 where the Meter was subjected to detecting incremental changes in flow rate of mud at different flow rates.

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