What is Casing Collar Locator(CCL)?

The casing-collar locator (CCL) is a crucial tool used for depth control in cased-hole logging operations. When paired with a gamma ray log, it enables the correlation of cased-hole logging runs with openhole logs, allowing for accurate identification of reservoir units or zones. This correlation is essential for subsequent downhole operations such as perforating. Due to its importance in providing primary depth control, the CCL is included in nearly every cased-hole tool string.

The tool itself consists of a coil-and-magnet arrangement with a downhole amplifier. The most sensitive of these arrangements involves two like-facing magnetic poles positioned on either side of a central coil. As the tool passes a location where the metallic casing is enlarged by a collar, the magnetic lines of flux are distorted, causing a change in the magnetic field around the coil and inducing a current within it. This signal is then amplified and recorded at the surface as a voltage spike, known as a collar "kick."

CCLs can be run in standard wireline logging mode or on a slickline, with options for pure-memory slickline CCLs, which record data simultaneously with other logging tools, and real-time slickline tools, which convert the voltage spike to a tension spike for surface detection. In coiled-tubing applications, CCLs have been modified to transmit pressure spikes through the fluid within the coiled tubing to the surface, as the heaviness of the coiled-tubing string makes it difficult to detect small tension spikes with confidence. Recent advancements have improved these tools for high-pressure/high-temperature applications.

Additionally, certain types of downhole tractors used in deviated wells have the capability to produce a CCL during their operation, providing the same depth control functionality. If you are interested in Vigor's Casing Collar Locator or other drilling, completion, logging equipment for the oil and gas industry, please do not hesitate to contact us for more technical details.