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Drilling top-hole with SOPBM and divertor only
04 October 2011
has anybody ever drilled surface hole with SOBM having diverter only? if justification is there for SOBM would you consider??, i.e directional drilling with high BU rate, positive no shallow gas and knowing for sure to to TD section and set casing before entering into hydrocarbon zone
4 answer(s)
Titiloyefemi
Drilling Fluids Engineer
Pishon BEFY Nig Ltd
Total Posts: 2
Join Date: 06/10/11
Edwin,
Using SOBM for Top hole, I don´t want to say it is not real. But let considerer these;
1. Degree of losses at sub surface(Down hole)
2. Environmental squalor as a result of Surface losses
3. Solids control & segregation problems (screen blindness) due to Cutting´s Water wet
4. Bit balling as a result of de-emulsification of Oil with water phase in Shallow shale.
5. Time & strength of building new/ replenish mud while experiencing Top hole losses
6. To cap it all Cost effectiveness is abortive
Hence for these few point amongst others I would have preferred some other special designed formulation on WBM for Top hole.
gregcrum
DSupt
CNR International
Total Posts: 23
Join Date: 17/05/08
Assuming you were in a region where the regulatory body was prepared to consider the idea you'd need some good hazard analysis and very robust mitigation measures.

Obviously a pilot hole would be a good idea unless this well is in an already heavily drilled area.

Worst case, you have a kick / blow out, what next ? You can't close the well in so a dynamic kill is your only option. You'll need kill mud (and a lot of it) pre-prepared...but you can't calculate the weight required as you have no SIDPP. What weight of mud will you use ? It is top hole, so will your formation take the kill mud weight ?

If you were to proceed and get it across the line with the appropriate authorities your risk analysis and justification will be an excellent document to share.
ianpetitt
(retired) Well Fluids Team leader
SPREADAssociates
Total Posts: 40
Join Date: 14/06/06
Edwin done on Kashagan as no discharge of even WBM into Caspian. In general not recommnded as :
  • Higher risk of sub-surface lost circulation both in magnitude and mud barrel costs.
  • Higher risk of surface losses due to incorporation of excessive volumes of water wet cuttings into the system leading to water wetting of the shakers.
  • Risk of bit balling and therefore complete absence of any penetration rate due to the incompatibility between an oil based mud system and extremely water wet young shale formations.
  • If pump capacity is limited inadequate hole cleaning with OBM and stuck pipe much more likely than with low inhibitive WBM.
MilapG
Drilling
Reliance Industries Ltd.
Total Posts: 14
Join Date: 28/11/05
using SBM at such shallow depth is not an established industry practice,although one could technically consider this as an option.
With ever increasing stricter norms of environment this needs very careful and meticulous execution and yet cannot be completely flawless. Safer fit for purpose options are existing - use of Brine based moderately shale inhibited system does the job safely enough.Costlier but more advanced optioon of using Shale inhibited system with RMR offer a better solution. Nevertheless it is certainly a different way of thinking and is welcome, provided the environmental norms allow and execution can be effected with perfection.
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