New Flow-through Mudmat Design for Heidrun Subsea Structure

Permanent or temporary subsea structures that require some initial or frequent on-bottom relocation need an effective mudmat release system. This is necessary in order to avoid problems that may arise due to pressure differences at the mudmat/soil interface. Through detail engineering work performed for the development of subsea installations at the Heidrun Field off the Norwegian coast, a novel mudmat design has been conceived that enables water to flow freely through the mudmat top without sacrificing overall stability or structural integrity. This was accomplished by integrating geotextiles and expanded steel mesh for support into the design. The design permits structure installation and removal keeping hydrodynamic forces, soil resistance and disturbance of the seabed sediments to a minimum. Hence, subsea dynamic behavior is more favorable reducing structural stresses, relocation time and the necessary lifting capacity of the surface vessel as compared to earlier solutions.