The Drift Test is a non-negotiable, universal quality assurance protocol across all phases of well construction. Its primary function is to verify Wellbore Integrity by ensuring the internal diameter of the OCTG (Oil Country Tubular Goods) remains unobstructed.
The principle is simple: to confirm that no component installed on the casing string will compromise the Minimum Internal Diameter, thereby guaranteeing the passability of subsequent toolstrings and equipment.
drift test: What it is?
The Drift test mandate originates from API Specification 5CT, which dictates the exact Minimum Drift Diameter for every casing size and weight. The successful execution of a Drift Test confirms that the component is ready for use in a controlled wellbore environment.
The test utilizes a precisely machined Drift Mandrel—a cylindrical gauge—with a diameter carefully set just below the specified minimum internal diameter of the casing.
The procedure requires this mandrel to be pushed through the entire joint of casing, including all installed accessories. Any snag, hang-up, or obstruction constitutes a failed test, immediately flagging the component for remedial action or rejection.
Why is the Drift Test Critical for Cementing Process?
The test is a proactive measure against high-cost Non-Productive Time (NPT) and catastrophic job failures downhole.
Avoiding Remedial Cementing
If a cementing plug encounters a tight spot caused by a protruding bolt or distorted accessory, the plug can stall prematurely. This prevents the plug from landing on the float collar, leading to insufficient displacement and a compromised primary cement job. The result is often expensive remedial cementing (squeeze cementing) to achieve zonal isolation.
Guaranteeing Toolstring Passage
Every subsequent operation—from running a BHA (Bottom Hole Assembly) to drill out the shoe track, to deploying complex completion toolstrings (like packers, safety valves, or liner hangers) requires an absolutely clear pathway. The Drift Test is the only physical verification that this pathway is guaranteed.
which parts need Drift Test?
The Drift Test assesses the unique risk profile of every type of accessory that interacts with the casing’s internal bore.
The Value of Certified QC
For a supplier operating under API Q1 certification, the successful completion of the Drift Test validates more than just a component’s size. It confirms that the entire quality system—from raw material sizing to final assembly procedures—is robust enough to ensure every tool delivered to the wellsite will uphold Wellbore Integrity and provide flawless support for the operator’s drilling and production phases.
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