Mechanical Integrity Testing

for Underground Caverns

An MIT is commonly performed to evaluate the mechanical integrity of a cavern’s wellhead, casing, tubing, and cemented annulus between the production casing and the formation at the casing seat area.   Generally, the test is conducted by injecting nitrogen into the well to below the casing seat at the desired test pressure. Brine and nitrogen pressures are recorded, and the interface level is located by running an interface detection tool.  This interface will be used to calculate and evaluate the well/cavern integrity.

BGES has developed a proprietary Gamma-Density Interface Tool, GDI-2, (patent pending) capable of detecting fluid interfaces behind 1 or 2 sets of casings. It is specifically designed to detect various types of gas-liquid and liquid-liquid interface in salt caverns.  The tool has a vertical resolution of up to 2” (or 5cm), and is approved by the CNSC with no well abandonment requirements if it becomes unrecoverable in a well / cavern.

For more information, please click here to view our interface detection tool page.


Applications

In accordance with the CSA Z341, prior to commissioning a new cavern or abandoning a cavern/wellbore, the MIT must be conducted to identify leaks in the wellhead seals, production casing, and casing seat.

Features and Benefits

The GDI-2 tool allows continuous reading of the interface and does not energize the formation. Real-time downhole pressure & temperature measurements can eliminate assumptions and approximations, which is greatly beneficial for MITs. Pressure and temperature data can be viewed real-time through satellite data streaming. Deliverables include a comprehensive written report for regulatory submission.

Operations

Typical procedure involves testing the well to the desired casing seat pressure with brine in the cavern well and with nitrogen in the cased section of the well and extending below the casing seat. During the test period, brine and nitrogen pressures are continuously recorded at the surface using digital recorders. The interface level is located by means of neutron surveys and must be accurately logged/recorded over a 1m section since it may shift upward or downward due to fluctuating conditions. Location of the interface, along with temperature and pressure measured, are used to calculate and evaluate the well/cavern integrity. BGES’ MIT system allows real-time viewing of pressure and temperature data online through satellite data streaming.