Cost-effective Thermal Insulation Systems for Deep- Water West Africa in Combination with Direct Heating

Long offsets and subsea tie-backs are becoming attractive scenarios for exploration and production of offshore hydrocarbon resources. Flow assurance associated with these field development scenarios is critical. As offshore oil and gas production pushes into deeper water, the risk of hydrate plugging of pipelines and flowlines continues to grow, as does the cost of remediating any such plugs. Conventional methods of preventing hydrate plugs, such as blowdowns, hot oiling and methanol injection are costly and not entirely reliable. For example, at locations where the subsea manifold is higher than the riser base, or locations where the flowline route has substantial high and low spots to trap gas, the process of venting gas is very complex. Conventional remediation techniques, requiring pressure blowdown, are also uncertain and it may take months to melt a hydrate plug. The standard industry practice is to rely on enough passive insulation to overcome both the cooldown over the entire flowline length as well as providing a means of holding the temperature inside the flowline wax and hydrate formation temperatures. This paper will examine the technical issues regarding use of polypropylene as the bulk material for flowline and riser insulation in deeper waters, particularly the 7-layer system which is used on several projects for deep water in the Gulf Of Mexico (GoM). Also, the paper will describe the prevailing opportunities with combination of polypropylene and direct electrical heating.