I'm not an expert on this but the purpose of passive fire and explosion protection in wellhead areas and other areas on an offshore platform is to ensure maximum possibilities for evacuating personnel from the area, and to minimise escalation of the accident (platform collapse etc)

I think the specific requirement in each case is based on the conclusions of a risk assessment for that field.

I have worked on several projects with wellhead platforms, all of them without drilling facilities. Typically these have had a firewall separating the wellhead area from the manifold area - not for structural protection but to provide a safe escape for people working in the manifold area. Structural firecladding (or deluge) have been provided sometimes where structural collapse could be a consequence.

In the norwegian offshore sector, all the design standards are available at www.nts.no/norsok.

I suggest you look at those and especially these two:

http://www.standard.no/pronorm-3/data/f/0/01/44/6_10704_0/S-001.pdf

http://www.standard.no/pronorm-3/data/f/0/03/92/8_10704_0/N-001.pdf

Also standard API RP 2A :
http://api-ep.api.org/filelibrary/Catalog_web.pdf

Finally (or most importantly) re-post your question to the Structural Engineering forum. I think you will get many answers from people with more experience in this field

regards
Mogens

Also take a look at ISO 13702 and check on any defined loss prevention policies for the development under consideration.

Steve Jones
Petroleum Development Oman LLC
Muscat
Sultanate Of Oman

The answer depends on your objective.  If the WHP facility is unmanned it is doubtful whether adding PFP would lead to any significant improvement in PLL (Potential Loss of Life) numbers.  It is therefore probably not justifiable to apply PFP on safety grounds alone.  However, PFP may still be required for asset or environmental protection.  

The best approach is to perform a fire risk analysis to determine probability and consequences of the envisaged fire events.  Then calculate the justified expenditure on PFP to avert or mitigate these consequences.  If the actual costs of applying PFP is disproportionately greater than the justified expenditure then it is normally permissible to omit the requirement for PFP.

As you are doubtless aware PFP is costly to apply, adds considerable weight and can make inspection of structures during operations difficult.  Generally it should only be applied where it is required by legislation or where it can be demonstrated as justified by risk analysis.