Oct.11tb, 2019
MESHD,MES-S and DHI jointly establish deep-water riser connection technology

Mitsui E&S Holdings Co., Ltd. (President and COO: Ryoichi Oka, "MES-HD") and Mitsui E & S Shipbuilding
Co., Ltd. (President: Tetsuro Koga, "MES-S") and Dai-ichi Heat Treatment Industry Co., Ltd. (President:Mitsuaki Sone, "DHI") , the only Japan manufacturing company of drilling pipe of oil and gas, have started tojointly develop deep-water riser connection technology.
The seabed of Japan's exclusive economic zone (EEZ) contains various natural resources including rare-earth
elements, shallow methane hydrates, sandy layer type methane hydrates, sea-floor hydrothermal deposits andcobalt rich crusts, and there are high expectations for future development with a view to harvesting thesematerials from the seabed as 100% domestically-produced resources. In the various resources, rare-earth
elements mud is located on the seabed at depth of 4000 to 6000m. It is difficult to apply the existing technology
of offshore oil and gas industry with a maximum water depth of 3000m to resource development of deeper than
3000m.
In particular, the riser pipe hanging from the ship to the seabed is one of the biggest technical challenges indeveloping deep-water for oil and natural gas, not just mud including rare-earth elements. The common joint
method of steel riser pipes is flanged connection such that the flanges welded at the end of the steel pipe are
secured together with bolts.
Since the total weight of the riser pipe becomes very heavy as the water depth increases, it is very difficult tohang the riser pipe from the vessel. So, the development of high-strength riser pipe that is able to reduce theplate thickness has been promoted in recent years. However, the flanged connection of riser pipe is required tohave a welding performance that does not cause a decrease in the toughness of the circumferential weld.
Therefore, the carbon equivalent of the material is limited and it is not easy to increase the strength.
In response, MES-HD and DHI have started the development of shrink-fit connection as a new riser pipe
connection technology.

Shrink- fit connection is a technique that a short steel pipe, connecting pipe, with an inner diameter smallerthan the outer diameter of the riser pipe is pre-heated and expanded, then left to cool after the riser pipe is inserted
from the both ends.
If shrink-fit connection is adapted as the joint method for the riser pipes, riser pipes with the shrink-fit connection
is lighter than those with flanged connection. In addition, the length of connecting pipe can be easily changed tothe optimum size at each joint location to decrease total weight.
Moreover, since the riser pipe itself does not have a circumferential weld, welding performance and fatigue
performance are not required. So steel pipes with higher strength than the standard steel riser pipe such as API
5L standard can be used to decrease the total weight of riser pipes.
In this way, shrink-fit connection is the technology that is expected to greatly increase the working water-depth
to 6000 m because the total weight of the riser pipe can be significantly reduced compared to conventional
methods.
We have examined the effectiveness of shrink-fit connections by conducting a tensile test of small-scalespecimens.
A strength experiment at the full size of riser pipe at a depth of 6000m is going to be carried out.
Shrink-fit connection is also expected to be an effective technology in the deep-water developmentof offshore oil and gas industries.
MES-HD has simulation technology of riser pipe behavior and has a wide track record in the
production of offshore structures. DHI contributes to the industries with high quality in themanufacture of drilling parts for oil and natural gas.
MES-HD and DHI will continue their activities with a view to deploying deep-water riser
connection technology to offshore oil and gas productions.