Complex well fingerprinting in SOBM?

27 May 2014 Recent deepwater campaigns (circa 2500m water depths), drilling sedimentary (porous permeable formations).

What was noted from the deeper horizons using exclusively flat rheology, SOBM, in notably 12¼" wellbores and downwards i.e. in to 8"" sections was as follows.

After drilling the section (e.g. for 2-5days) and prior to trip and POH. Significant flow back trends resulted and many hrs were required for well to settle out!. e.g. Sometimes gaining and sometimes loosing. End result was many hours were spent flowchecking until everyone was confident to keep pulling. (because no one could provide or predict expectancy flow back or loss outcomes!)

Recent papers however from HPHT wells state these trends can be predicted. i.e. through use of drillbech and/or other similar high end PVT capable hydraulics software modelling. 

So firstly are there any engineers out there, using predictive methods to what to expect at the end of drilling in these complex wells? If not, why not?

My current thought train on current project, as i expect similar events, is to develop better finger printing practices at the start of drilling and then to apply better controls (on connections) to the end of the section. Where as this is essentially a cycle of PVT, heat/energy exchange events. i.e. we start with a riser full of majority of mud at a certain temperature at a certain mud weight. We drill and rotate and boost riser (with warmer mud), for 3-5days where PVT effects will change, plus mud weigth may change, all that we should be able to see somewhat through finger print changes. Note: a 1-2deg change in temperature in a 4,000bbl active mud system system is a 40-80bbl discrepancy!

At the end of section, we generally have to wait (many hours) until equilibrium re-establishes to be assured well is not flowing or loosing which is they key point to 'effective well control' in all of this and why improvements in my view are required.

i.e. we need to be able to monitor these trends more accurately so we can recognise at the earliest opportunity if a well is flowing or loosing or not!

Where in a recent well everyone assumed at the end of drilling the section all was OK (because trip tank indicated a straight line) (however a loss should have been the end result!!!).

Thus it was a long time until it was realised a kick was in effect.

Therefore complex wells need far smarter, better practise resolution, where any best practices, comments, experiences welcomed.

regards,

Peter.

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