Planning optimal well design: Mitigating risks of drilling through abnormal pressured lenses

This item crops up on numerous well designs, how to mitigate the risk of abnormal pressure lenses particularly in the intermediate/production sections to maintain an optimal well design.

The scene: One offset in the area encountered an abnormal pressure lens, took a kick and the same zone may or may not be present on your location- but can´t be discounted. 9 times out of 10 you don't see anything when you drill them.

Planning: when designing the well do you push on and drill through to next section TD accepting the potential performance risks, high overbalance, low ROP, losses, unable to reach TD or  do you deal with potential abnormal pressure lens and isolate it requiring extra string, cost and time.

I would like to know if there is a more pragmatic approach and understand the merits of particular strategies used by members in the group. 

Some of the risks:
1) high overbalance - subsequently performance risks drilling ahead
2) hole size (17-1/2”)- ability to dynamically kill abnormal pressured lens
3) kick tolerance (surface casing)

Mitigating Strategies:
1)  Accept high overbalance and drill ahead (high risk of low ROP), set decision tree options Drill ahead, set liner/ casing could be planned based on depth, ROP and time.
2)  Plan to drill through and case off with extra string/liner, lower MW  
3)  Plan to drill through take pressure points confirm yes/no pressured and adjust MW 
4)  Push surface casing as deep as possible or extra string for kick tolerance
5)  Drill different hole size (slim) to dynamically kill it- dedicated pilot hole 
6)  Is there any lookahead tools on the market that can provided added value in the assessment of the lens being abnormally pressured?

4 Answer(s)

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