Flow Control, Flow Control November 2017

Left Two different foam compositions installed on pipe to guarantee additional annular volume All images courtesy of Trelleborg Offshore casing annulus to expand One such solution currently available is called crushable foam wrap CFW a collapsible material manufactured from a rigid polymeric material with a closed cell foam microstructure Classified as a Type II mitigation technique CFW is a passive APB mitigation system specifically designed to collapse within a specified temperature and pressure envelope This collapsible barrier is typically installed on the casings outer wall within the B or C annuli of a subsea well before being immersed within the annulus fluid This displaces the liquid in the casing annulus when the well is completed When heat from drilling and production operations cause the trapped liquids to expand the collapsible barrier acts as a mechanical fuse and collapses within a predetermined pressure and temperature envelope allowing expansion of the annulus fluids and dissipation of any potentially hazardous pressure increases Installing a collapsible barrier in the casing annulus could prevent catastrophic failure from happening before any potentially dangerous pressure occurs Designed to collapse CFW is designed to collapse within a narrowly specified temperature and pressure envelope which defines the upper limits of pressure and temperature for the well This increases the remaining volume in the annulus and facilitates a pressure reduction In the startup phase the CFW remains intact with no significant volume change unless the temperature increases beyond the predetermined pressure and temperature collapse criteria As the pressure and temperature in the well rise during operations the materials begin to compress and relieve pressure in the narrow confined space of the annulus If conditions reach certain preset limits the CFW undergoes a progressive and significant collapse preventing excessive overpressure and thus Above Classified as a Type II mitigation technique crushable foam wrap collapses within a specified temperature and pressure envelope Right Collapsible barriers like crushable foam wrap are installed in the casing annulus protecting the steel casing from failure The crush mechanism occurs well before the casing collapse pressure preventing excessive overpressure and reducing the risk of cracking Normally in a fully sealed annulus once the foam is crushed additional crushing cycles are unnecessary However to protect the steel casing from a possible second pressure increase different foam compositions can be installed to guarantee additional annular volume Free info Enter 210 at fcm hotims com www flowcontrolnetwork com November 2017 25