Albina,"At the moment this is high level planning and idea discussion, and so we would be really interested to understand the experience that others out there have and how they managed this."
With so little data provided we can only assist in how to take a candidate well and work this through several base concept design options (some of that have been mentioned in other posts). All to work toward the preferred 'Option' for all the right reasons, to deliver a final basis of design selection ( with contingencies often needed). A safe, yet operational realistic pressure management and well control Assurance plan to dleiver outcomes and benefits desired.
I would use of the IADC MPD candidate selection process and tools provided to us by our peers to work through all well drilling concepts on offer ie Section by section from designs to a base case design. A good comparison is always to have a standard regional well ( what you are doing now and List all current hazards/risk problems you are having) or anticipate to weigh all the 'SWOT' analysis, Strengths, Weaknesses, Opportunities and Threats that you could also conduct.
IADC Well Classification System for Underbalanced Operations and Managed Pressure Drilling
The purpose of the IADC Well Classification System is to describe the overall risk, application category and fluid system used in underbalanced operations (UBO) and managed pressure drilling (MPD). Wells are classified according to:
• Risk Level (0 to 5)
• Application Category (A, B or C)
• Fluid System (1 to 5).
This classification system provides a framework for defining minimum equipment requirements, specialized procedures, and safety management practices.
For further information? simply refer to the IADC UBO HSE Planning Guidelines and other related documents
So there is a good guide to assist.
Also Get a few specialists involved and run a on-line workshop. This would be upfront loading money well spent.
The design hinges on whether you expect or are wanting returns or if you have a loss zone to deliver cuttings into. You have not stated this?
With returns a light weight fluid can be used but you have to know your drilling limits as others have posted. Particularly if wellbores are large and inclined. ROP and hole cleaning in certain formation types will also have to be Strictly controlled. There are generally always operational limits and constraints that need to be well modelled and understood. Bit bha design is paramount.
if you are taking cuttings returns, You required also high efficiency solids control equipment to remove cuttings at shakers. Upgrades likely needed here? Knowing All these limits are therefore paramount and must be included in your hazard risk assessments concluded here!
If you have a loss zone to take the cuttings then annular pressure can be maintained by using a mud cap or pressurised mud cap Systems approach as other have stated. This is commonly used in these regions and there are specialist companies that can aide and assist working you through the concepts to final design processes stages needed. You can now use a more managed pressure just above balance drilling method to drill more effectively and efficiently yet maintain annular pressure for losses and gains etc.
Time doing this properly is money well spent,
The end result is that you need to assure yourself that you have enough strings of casings and sufficient drilling operating Window margins to be able to proactively drill and mitigate to expected worst case expected conditions vs a respond and react and cure process.
The MPD solution selected needs to assure that you can indeed ‘Make Problems Disappear’ in terms of pressure management and well control assurance issues currently experienced with a solution that can safely effectively and efficiently resolves your issues.
Lots of pre and detailed planning, getting the right people and training all involved, peer assists and reviews, right tools and equipment at the rig and downhole to best meet each section to be drilled. Getting the numbers right first time, is paramount, truly knowing your limits , real hazard / risk management checks along the way, to result in the most practical yet evidence based and well engineered solutions are all part and parcel to achieve safe effective efficient wellbore delivery.
If it was me assigned to this task, I would be picking up the phone and seeking specialists help and advice on all of the above.