A mechanical integrity test is the pressure test that proves an injection or disposal well has no leak path between its tubing, its casing, and the packer that seals the space between them - the assurance that injected water is going where it is supposed to and not escaping into a protected zone. It is a regulatory requirement for injection wells, and it is one of the clearest cases where a routine pressure test and continuous monitoring guard groundwater. This guide explains what the test proves, how the annulus pressure test is performed, and how ongoing annulus-pressure monitoring supports it.
Mechanical Integrity Test in one line: A mechanical integrity test, or MIT, is a required pressure test that demonstrates an injection well has no significant leak between the tubing, the casing, and the packer; in the common annulus pressure test, the sealed annulus between tubing and casing is pressurized and monitored for a set period, and holding pressure with no significant loss proves the well is mechanically sound.
A typical injection well is built with concentric barriers: water is pumped down an inner tubing string, the casing surrounds it, and a packer near the bottom seals the annular space between the tubing and casing so injection stays inside the tubing. The space above that packer, between tubing and casing, is the annulus. Mechanical integrity means those barriers are intact - there is no leak in the tubing, no leak in the casing, and the packer is sealing - so injected fluid cannot escape sideways into a formation it is not supposed to enter, particularly a fresh water zone.
The mechanical integrity test is what demonstrates that internally. In regulatory terms, internal mechanical integrity is the absence of a leak path in the tubing, casing, and packer, and it is the piece the annulus pressure test directly verifies. Proving it matters because a disposal well's whole purpose is to isolate the injected water in a deep permitted zone; a leak through a failed tubing joint or a bad packer could route that water toward a shallow aquifer. The MIT is the periodic check that the well is still doing its containment job.
In an annulus pressure test, the annulus between the tubing and casing is filled and sealed, then pressurized to a specified test pressure using an external pump. The well is isolated so that the annulus is a closed volume, and the pressure is held and watched over a defined time period while it is recorded. If the tubing, casing, and packer are all sound, the sealed annulus holds its pressure with only minor changes attributable to temperature. If any of the three barriers leaks, pressure bleeds off and the well fails the test.
The recorded pressure trace over the test period is the evidence: a stable line means integrity, and a decaying line means a leak that must be found and repaired before injection can resume. Temperature effects are accounted for because trapped fluid expands and contracts with temperature, which can move the pressure slightly even in a perfectly sealed annulus. The test is run to a defined procedure - a set test pressure, a set duration, and an allowable pressure change - so that pass and fail are objective rather than judgment calls, and the record can be submitted to the regulator.
A periodic MIT proves integrity at a moment in time, but many injection wells also carry a continuous annulus pressure gauge so that a developing leak can be caught between scheduled tests. In normal operation the annulus is typically kept at a stable pressure, and a persistent, unexplained change in that annulus pressure is a warning that the barrier system may be degrading. Watching annulus pressure continuously effectively extends the assurance of the MIT into the time between tests.
Merobix, as a cloud SCADA, reads the digitized annulus pressure tag from the well's controller over a protocol such as Modbus or DNP3 rather than connecting to the gauge directly, and it can trend that pressure continuously and alarm on an abnormal change. A remote operator can watch annulus pressure across many injection wells, catch a slow decline that suggests a developing tubing or packer problem, and keep the logged history that supports the well's integrity record. During a scheduled annulus pressure test the same data path captures the pressure trace cleanly, so the formal MIT and the day-to-day annulus watch reinforce each other - one proves integrity on schedule, the other guards it in between.
It checks that there is no leak path between the tubing, the casing, and the packer, so injected water stays inside the tubing and cannot escape sideways into an unintended zone. The common annulus pressure test verifies this internal integrity directly. Passing the test demonstrates the well's barriers are intact and it can safely continue injecting.
The annulus between the tubing and casing is sealed off, pressurized to a specified test pressure with a pump, and held for a defined period while the pressure is recorded. A sound well holds pressure with only minor temperature-related change, while a leak in the tubing, casing, or packer shows up as pressure bleeding off. The recorded trace is the evidence of pass or fail.
The scheduled MIT proves integrity only at the moment it is run, while a continuous annulus pressure gauge can catch a leak that develops between tests. A stable annulus pressure indicates the barriers are holding, and a persistent unexplained change is an early warning of a developing problem. Continuous monitoring effectively extends the assurance of the periodic test across everyday operation.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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