Mudline Suspension System & TOC Challenge

Dear All

We are planning for an offshore well in shallow water (150 ft) with jack up rig. Well design comprises of 30" conductor (@ 450ft) x 13-3/8" surface casing (@5000 ft) x 9-5/8" (production casing) x 7" (production liner). It will be suspended with MLS for re-entry purpose and surface wellhead system / BOP  will be used during drilling.

We have policy requirement of cement to surface for surface casing but the surface section poses serious threat of total losses and induced water kick. TOC below the MLS level or inside conductor is very difficult to achieve and I dont have the luxury of top job with MLS system. So this adds up to well complexity.  Few options that I have brainstormed are:

Option 1: Revise well design and introduce additional 20" or 18-5/8" surface casing and set above loss zone. TOC to sea bed is achievable but its much costlier in terms of drilling days and materials.

Option 2: Use two-stage cementing with Pack off stage tool in 13-3/8" and inflate packer from 13-3/8" to 30" conductor. However such a packer is really hard to find that can go for such extended inflation from 13-3/8" to 30".

Option 3: Use a combination of 30" x 20" (last two joints) conductor and inflate 13-3/8" pack off stage tool across 20" conductor. Can this option pose a risk of conductor structural integrity if 20" joints are introduced and "cemented"?

In both options 2 and 3, there is a big "what if" about packer failure to inflate for whatever reason.

I would like to ask members what other possible options do I have or what their experience suggests if they have been through a similar situation when TOC was a challenge with top job constraints in MLS.

Thank you.

12 Answer(s)

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