Thermal insulation of pipelines and associated equipment is one of the primary methods used to retain heat and prevent hydrate formation during an unplanned shut down. During the process of qualifying equipment for a deepwater project with hydrate concerns, thermal insulation for a flowline connector was analyzed using Thermal Finite Element Analysis techniques and tested using a physical test representative of field conditions. When the results initially fell short of expectations, an extended program of redesign and analysis was performed.
This paper reviews the background and the methods of hydrate control concentrating on field installable insulation. It then presents the case history of the qualification of a specific insulation system. This review includes the analysis used to evaluate the performance of the insulation, the test methodology used to validate the equipment, and a correlation of the data that was collected during the testing.
Testing is required to gather the empirical data to describe the characteristics of thermal materials. This elemental data is used to predict the performance of more complex thermal systems. Further testing is then required to validate the complex thermal models. During this process, the answers obtained are often are the seeds for additional questions.
A corollary of the current deepwater evolution is that the wells tend to be miles from a surface facility. This is only possible as a result of a combination of technological developments. Along with the new capabilities come new challenges. Most are anticipated, but occasionally the challenges are not obvious and the solutions can be initially illusive.
Drilling techniques are continually improving and the physically capacity of vessels that perform the work have been upgraded to keep pace with the increased demand. Depth records for drilling exploration wells are broken as fast as they are made. The vessels required to install the production equipment and pipelines have developed in parallel allowing them to keep up in the depth record competition.
The depth of the water makes it impractical to install processing facilities at the production location. Water depths have long been too deep for even innovative platform designs. Floating production facilities which redefined deepwater are also not practical in the ultra deepwater.
As the drilling depths increased, control systems progressed from direct hydraulics to multiplex systems using combinations of electrical, hydraulic, and sonic controls.
These developments in remote control and communication equipment also provide increased confidence, allowing the production fields to move even further from the source of control.
The increased remoteness of the production trees and manifold from a processing source has also introduced a new set of challenges in the area of flow assurance. These are the build up of wax and the formation of hydrate blockages. These two problems are similar in that they have both become a concern at temperatures of the pipeline system well above subsea temperatures. The hydrate formation is typically associated with a temperature drop when the pipeline is not operating, i.e. during a shut in of the pipeline.
