Slim riser technology offers potentially significant cost savings for many applications. Mark Childers, general manager – technology for Atwood Oceanics, told participants at an International Association of Drilling Contractors meeting in Houston. The slim riser saves money in a number of ways, he said.
Atwood's slim riser has a 16-in. outer diameter (OD) as opposed to the conventional 20-in. OD on standard risers. The reduction in size reduces the amount of storage space needed, the variable deck load required, and the amount of mud used, Childers said.
Childers outlined the pros and cons of Atwood's slim riser, beginning with the disadvantages. The up-front cost is $14-18 million, and lead time for ordering is seven to nine months. Furthermore, in some applications, slim risers are not the best solution, he said.
On the other hand, slim riser technology allows a third- or fourth-generation semisubmersible to perform work that would otherwise require a more costly drilling rig, Childers said. The technology allows standard subsea well control and can be deployed in mild to severe environments. Slim riser technology is applicable for a single ultra-deep well or for a template. Another significant feature is the riser's ability to easily mate with a conventional riser, he said.
According to Childers, testing in the Mediterranean using the semiAtwood Eagle has proven the viability of the slim riser design. Though Atwood's slim riser has been about three and a half years in the making, "Technologically, there is nothing new, here," Childers said.