Effective long-term management of oil and gas wells is possible only through timely monitoring of tubing and casing integrity. GR Energy Services offers monitoring with the TGT Magnetic Imaging Defectoscope (MID), which effectively detects and quantifies corrosion of tubing and casing in one trip in wells with up to three barrier completions without pulling the tubing, descaling and dewaxing the wellbore, or changing wellbore fluid properties.
The MID tool comes with either two or three sensors—short, medium and long. Each sensor has a pair of electromagnetic coils, a generator and a receiver. These coils generate high-energy electromagnetic pulses, and the rate of decay of the created magnetic field is recorded over time.
The choice of running a two- or three-sensor tool depends on the number of barriers to be investigated.
Field disturbances caused by defects in different barriers surrounding the tool differ in decay times, enabling separate visualization of each barrier. Metal loss in either of the two innermost concentric barriers is quantified using a thickness simulation computer model.
The complex responses and precise detection of metal thickness variations in three individual pipes are interpreted via accurate numerical modeling.
In addition to thickness logs, the MID software can identify electromagnetic signatures of various completion components such as packers, X-nipples and sliding side doors (SSDs).
The Magnetic Imaging Defectoscope clearly identifies a hole in the 3 1⁄2‑in. tubing.
The log example below illustrates MID logging results in a two-barrier case—a casing and a tubing. The short-sensor data panel (near delta) accurately displays tubing collars and indicates that the tubing is in good condition. The long-sensor data panel (far delta) shows casing collars in blue, less distinct because it is farther from the tool. An anomaly detected in Zone 1 indicates corrosion in the 9 5⁄8-in. casing.
Additionally, an X-nipple in Zone 2 is clearly identified as metal loss in the tubing thickness profile, and as horizontal brown and blue bars in the near and far delta panels. The perforations in the 9 5⁄8-in. casing are accurately picked up, as shown in the far delta panel and the casing thickness profile.
Corrosion detected in 9 5⁄8-in. casing through 3 1⁄2‑in. tubing in zone 1.