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Well Design Optimization
15 April 2017
Dear All,
Need your opinion on the optimization of a well.

Data :
1300 m Depth
Surface Casing - 9-5/8" = 450 m [Spud Mud is used]
Production Casing -7" = 1200m [ PHPA Mud]
Production Liner - 5" = 1300 m [ KCL Polymer- Drilled Blind in case of severe losses]

Now, the surface section is drilled to the first known gas zone, and it is drilled without a diverter, and drilled with spud mud within a day or two. The second section is drilled within 4-5 days which has two shale zones that need to be cased off as soon as possible.
The third section is drilled within a day in the payzone,which is a highly depleted limestone formation [ ~ 800 psi], hence the additional hole section.

Now, there was an option of combining the last two section and then cementing using stage cementing, but it has its own drilling risks, in case of losses, the whole section above it would loose the hydrostatic.

The well takes around 12-14 days at an average, and we need to reduce it more, the flat times have been optimized at max. Bit designs have been as aggresive as they can be and we control the ROP at times.
Need to know if anyone of you has any suggestions for further optimizing the well design. 

1 answer(s)
Senior Drilling Engineer
NRG Well Management Ltd
Total Posts: 17
Join Date: 01/09/15
I have looked at the well design. From what brief information you have provided it is difficult to optimise. I am outlining the following assumptions from what I understand.
1) This is a land well
2) BOP's are llatched after the 9-5/8" casing is set and cemented
3) The rest of the sections are drill through this BOP without lifting it.

If all of the above are correct the well design is optimised.
Of course the reservoir engineer would specify the production hole size requirement.

Otherwise if you wish to further reduce your time it will come at a cost of implementing casing while drilling or Managed pressure drilling which I am very sure will give you marginal gains.

Very intresting. Would be very keen to know more detail
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