Requirement for wiper trips subsequent to Wireline MDT pump out for fluid sampling

17 October 2014 I am looking for support and advice on a similar subject raised in 2009, but didn't get me the answer I am looking for.

This question below posed to me by one of our Well Engineers;

I have been trying to understand if a wiper trip is always required after running MDT logs. The main risk of not doing a wiper trip is a potential loss of overbalance should gas breakout at surface i.e well control

I have applied some conservatism in my calculations  by using Boyles law + single gas bubble to surface (oil in actual fact) + no gas solubility in OBM  to estimate the potential  reduction in  bottom hole pressure should gas bubble breakout at surface.

My theory is that if we are able to still maintain > 50psi overbalance in this calculation, then we should be happy to circulate conventionally up the riser. With all these conservatisms applied we should be confident with our overbalance calcs.

So my question are

Why aren't we confident not to perform a wiper trip after MDT logs if the calcs show we are fine?

if we are still not happy with the risk of unloading the riser, why can't we introduce some operational controls such as closing the diverter  and or annular after gas is circulated above BOPs?

Or better still, can't we run the casing and circulate gas up via the choke and kill lines?

We have empirical evidence of NOT seeing any gas cut mud at surface in over 20 cases where we  have done a dedicated wiper trip.  In deepwater operations it cost approx.  $3 MM per well to do a dedicated wiper trip .

Will be happy to know how other operators approach this.

8 Answer(s)

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