Coiled Tubing Depth Measuring System

Depth is the most important measurement made at the wellsite, yet conventional mechanical counters are often inaccurate due to pipe slippage past the single small-diameter friction wheel. The depth measuring system (DMS) employs proprietary software-controlled slippage compensation for a significantly more accurate measurement of the length of coiled tubing spooled.

Data manipulation module

The display module is mounted in the control cabin of the coiled tubing unit and is used to display and reset depth and speed. It also houses the onboard processor that runs the fastest-wheel algorithm (FWA). Digital display meters show the measured depth from the top and bottom wheels as well as the composite depth from the FWA. Quadrature signals can be fed to any data acquisition system. The three connectors on the right side of the display are the outputs to any data acquisition system (DAS).

Cutting-edge technology

The DMS is a precision measuring instrument that is designed to be quickly and easily installed or removed from the coiled tubing prior to transport. Whereas an ordinary depth counter’s accuracy is hindered by depth wheel slippage, the DMS design works to alleviate this in three ways:

• A lever-arm movement is used to maintain a high frictional contact force between the measuring wheels and the tubing.
• Two tungsten-coated stainless-steel measuring wheels are used for accuracy and dependability in harsh operating environments.
• A microprocessor is incorporated to run the FWA while continually monitoring the speed of both wheels’ electronic position encoders. The bottom wheel serves as master depth, and the top wheel serves as backup depth. The top wheel takes over as master when the bottom wheel’s speed is slower from slippage. The DMS displays a "composite" depth value.