Among the many applications of Coiled Tubing (CT) services, milling plugs and wellbore sand cleanout are two of the major applications. The transport of solids to the surface, as well as monitoring the return rates, are two sources of information which can have a significant impact on the execution of these jobs. Traditionally the flowback crew communicates this information to the CT control cab upon request. However, by utilizing an acoustic monitor and ultrasonic flowmeter, it can reduce the dependence on flowback operators and provide real-time solid measurement and return flow rate. The acoustic monitor is a passive, non-intrusive device that is designed to measure the acoustic noise induced into the pipe wall as solids impact the inside wall of the pipe. The ultrasonic flowmeter is a clamp-on device that is designed with two transducers that serve as both a transmitter and receiver.

In order to prove the concept, five stages of trials were planned and executed. In stage one, CT was rigged into a 150m vertical test well. The equipment included CT mast unit, CT pump, choke manifold, and acoustic monitoring device. Several debris piles from previous milling operations were introduced to the test well, and a CT cleanout was performed. The acoustic monitor system measured the amount of solid to surface, and the results were evaluated. Solids retrieved were then compared to the initial debris piles and correlated to the data received by the acoustic monitor. On the 2nd stage, the acoustic monitoring device was utilized in actual milling operation. The 3rd stage was a yard trial of ultrasonic flowmeter using a CT pump and data acquisition system to evaluate the working envelope of this device, followed by a field trial, in stage 4, utilizing the flowmeter in actual milling operations. The final stage of this trial was planned and executed in milling operations on a five wells pad, utilizing the combined applications of acoustic monitoring (solid measurement) and ultrasonic flowmeter (return rate) devices.

All five stages contributed to proof of concept for the applications of solid measurement and return flow rate devices. These trials were successfully planned, executed, and evaluated. The acquired data throughout the five stages of these trials were utilized during and post job operations as lessons learned to optimize the process for future applications.

The real-time measurement of solids and flow rate monitoring, independent of flowback operators, enables the CT operator to make informed decisions throughout milling and cleanout operations. The real-time streaming of solids to surface and return flow rate enables the operator and service company’s Engineering team to evaluate and optimize the execution of milling and sand cleanout operations.

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