Well integrity/control

Conductor-Integrity Monitoring in Subsea Wells in Harsh Environments

Over a 10-year period, sensors monitoring the motion and loads near subsea wellheads have been mounted on more than 300 drilling campaigns. Integrity parameters were calculated to assess whether subsea conductors provided the intended amount of support during drilling operations. In several of these campaigns, loss of conductor support due to integrity issues was observed.

Illustration of soil and cement support around an unsupported conductor.
Fig. 2—Illustration of soil and cement support around an unsupported conductor. An intact well is shown on the left, and a well with a fully developed trumpet-shaped hole is shown on the right.

A decade-long project to monitor drilling operations on subsea wells in harsh environments has delivered interesting results.

Subsea production and exploration wells are subjected to loads from the drilling riser and subsea blowout preventors (BOP). The latter have grown in size and weight over time, resulting in larger wellhead loads.

The main task of a subsea conductor is to transfer these loads into the seabed. The bending load applied on the wellhead is transferred into the conductor, which again transfers the loads through the cement and into the soil.

In cases where the load exerted on the soil and cement exceeds the capacity, the soil around the conductor might fail. The cement filling the cavity between the conductor and the soil can also crack and consequently lose its intended function. This support degradation reduces the conductor’s ability to support the well.

Case Study sidebar What is SWIM?

4Subsea’s Subsea Wellhead Integrity Monitoring (SWIM) service for operations on subsea wells has now been in action for more than a decade.

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