Casing inspection is an important practice to minimize the failure rate. Reducing failure rate is important because failure of a casing can be a danger to people and the environment; as well a can be more costly to repair than preventative maintenance. Types of casing failure inspective tools are: Deformation and/or fractures caused by pressure and temperature, Corrosion due to acids and natural wear and tear.
The following four types of casing inspection tools are about to give data and monitor for potential casing failure:
- Cased-Hole calipers lie inside the bore hole and have caliper fingers that are spring loaded to apply push against the internal circumference of the casing. The Caliper fingers will send measurements of the amount of spring release it takes to retain that same rate of pressure against the internal casing, it will send this measurement many times a minute, alerting any change in the thickness of the walls. The downfalls of this tool is that the constant pressure on the casing wall from the caliper fingers, can cause erosion and damage in itself and therefore the pressure levels the springs of the fingers is initially set at is of high importance.
- Flux-Leakage tools that use an electromagnetic field to monitor the casing. An electromagnet is fitted inside the casing, the fluctuation of the electromagnetic field is able to permeate through the casing. Then it is analyzed for any changes. Changes in the strength of the electromagnetic field leaking through the casing gives information about thinning of the walls of the casing due to metal loss, corrosion or damage.
- Electromagnetic Phase – shift tools that use an alternating magnetic field transmitter coil which communicated with a receiver coil, sending the electromagnetic signal back and forth through the casing allows this tool to monitor the circumference of the casing. Monitoring the circumference of the casing makes it possible to judge if there is any metal loss or corrosion causing a change in the thickness of the casing. However this method has its limitations, as it only monitors about a foot of the casing at a time it is far less efficient than other methods. Therefore, this method is usually used to find areas of large damage and/or corrosion and less effective at finding smaller intricate damage.
- Ultrasonic tools send ultrasonic waves down the length of the casings and based on echo and travel time they are able to give information that can somewhat draw a picture of the casing and be analyzed to show the thickness of the casing. This tool is able to communicate any damage or metal loss as well as send information about buildup on the casing. In conclusion, casing inspection tools are a necessity to prevent casing failure and protect people, environment and bottom line cost of running. These tools allow for monitoring and inspecting casing to make sure that their integrity is strong and their risk of failure is as low as possible.