Drilling and Cementing to Isolate Productive Series and High Pressure Zones: A Successful Case History Enables Zonal Isolation in High Pressure Gas Well with Close PPFG margins in South Caspian Basin

1. 1
31 October – 2 November 2018
Astana, Kazakhstan
SPE-212071
Drilling and Cementing to Isolate Productive Series and High Pressure Zones:
A Successful Case History Enables Zonal Isolation in High Pressure Gas Well
with Close PPFG margins in South Caspian Basin
Apparao Cherukuri, Elshan Ismayilov, Elgun Zeynalov,
Elkhan Karimov, Fuad Jabbarov, Vusal Iskandarov

2. 2
31 October – 2 November 2018
Astana, Kazakhstan
Objective:
• Experience of how 7-5/8” section was drilled, and cased-off to enable the zonal isolation in the depleted
VII horizon and high-pressure zone with close PPFG margins by managing high risks of differential sticking
and loss of circulation at one of gas-condensate reservoirs located in South Caspian Basin which is one of
the most complex high-pressure fields with close PPFG margins in the world.
• How the lessons learned from offset wells were applied in the latest development well in the high-pressure
gas-condensate field
Introduction

3. 3
31 October – 2 November 2018
Astana, Kazakhstan
• The high pressure gas-condensate reservoir is
located in South Caspian Basin, is one of the most
complex high-pressure field in the world, with close
PPFG margins and reactive clay in the overburden.
• The main reservoirs of the field are V Horizon, VII
Horizon and VIII Horizon.
• Due to the reasons that significant production in the
field was from the productive layer called VII
Horizon, high depletion is generally observed across
the formation during drilling operations raising NPT
compared to the whole drilling time due to
differential sticking and interbedded formations
with varying formation pressures.
High Pressure gas-condensate reservoir
Picture 1: South Caspian Basin

4. 4
31 October – 2 November 2018
Astana, Kazakhstan
• VII horizon mainly covered with 7 5-8” drilling
liner,
• Some of the remarkable difficulties encountered
during drilling through VII horizon in offset wells
that extremely raised NPT compared to the
whole drilling time due to differential sticking
and interbedded formations with varying
formation pressures,
• To meet the drilling targets from the field,
comprehensive practical solutions were planned
to be applied in the next drilling campaign.
General Construction Philosophy
Picture 2: General Construction Schematics for this high pressure gas-
condensate field

5. 5
31 October – 2 November 2018
Astana, Kazakhstan
Drilling
Campaign
across
depleted
VII
horizon
3 Predicament due to having weak zone at the shoe
This high pressure gas zone should be definitely isolated together with VII horizon
so as to allow safe drilling through the reservoir section, the target VIII horizon
4 Loss of circulation
Loss of circulation drilling across the reservoir section if having weak zone below the
previous casing shoe
2 High Pressure gas zone
High pressure gas zone below depleted VII horizon which required high MW to
stabilize the well by triggering differential sticking risks
1 Differential sticking and Stuck Pipe
High risks of differential sticking and stuck pipe across sand layers of depleted VII
horizon
Compilation of Key risks

6. 6
31 October – 2 November 2018
Astana, Kazakhstan
In order to minimize these risks, some preliminary
attempts were made. The first and utmost plan
was:
 Using two MWs for dynamic and static
condition while drilling and casing running,
cementing operations:
 1.80 – 1.82 sg - Low MW for dynamic
condition during drilling, UR and
cementing operations,
 1.93 sg – High MW for static condition
during POOH drillstring and casing running.
 Not displacing high MW at the TD but at the
previous casing shoe if required when drilling
high pressure gas zone below VII horizon.
Key Practical Solutions
Picture 3: Active fluid in the well, first one for static condition during casing
running and POOH the BHA, and second one for dynamic condition during
drilling, UR and cementing operations

7. 7
31 October – 2 November 2018
Astana, Kazakhstan
 BHA optimization by including accelerator into
the BHA and locating the jar across inside the
casing as previously jar was stuck across VII
horizon zones as well.
 Stuck pipe response was given special attention,
and crew was alerted especially during drilling
through this interval as drilling was planned to
be performed across this very challenging zone.
 Minimizing static duration of BHA at the TD,
and stationary time across the OH section by
minimizing connection time and by maintaining
rotation during any stoppage when possible.
Key Practical Solutions
Drilling BHA
Length - 300 m
Jar located at 230 m
UR BHA
Length - 250 m
Jar located at 185 m
Open Hole
Expected OH length was
170 m
Drilling BHA UR BHA
Picture 4: BHAs used for Drilling
and UR operations

8. 8
31 October – 2 November 2018
Astana, Kazakhstan
Picture 5: Real-time composite logs information while drilling through high pressure
gas zone below VII horizon
Operational Summary
 Drilling performed with low MW across VII
horizon and high pressure gas zone below it,
 While penetrating high pressure gas zone,
Downhole Stick Slip Indicator showed quite
high value, supporting very high risk of
differential sticking
 Increase MW to 1.93 sg at previous casing
shoe before POOH the DS,
 UR OH to 9 7/8” with 1.82 sg (ECD of 1.89 sg)
 Again displace well with 1.93 sg before POOH
UR BHA.

9. 9
31 October – 2 November 2018
Astana, Kazakhstan
Master log for OH
Depleted
VII horizon
High Pressure
gas zone and
liner setting
depth
Picture 6: MasterLog indicating GR, Resistivity logs, lithology, and real-time drilling parameters

10. 10
31 October – 2 November 2018
Astana, Kazakhstan
Operational Summary
 RIH 7 5/8” liner on DPs to the previous
casing shoe,
 Displace well with 1.82 sg at the previous
casing shoe,
 RIH to TD, and performed one BU
circulation to circulate out the gas,
 Cementing and Liner hanger activation
operations,
 1.88 sg MudPush, 1.92 sg slurry used
Picture 7: Decision Tree for running 7 5/8" Drilling Liner

11. 11
31 October – 2 November 2018
Astana, Kazakhstan
CBL to assess the cement presence behind the liner
Successful drilling into the reservoir section
• Good zonal isolation across OH zone: OH interval has good bond
long result per CBL/VDL;
• Good 7 5/8" shoe integrity to drill next section: No flow was observed
after the job and hard cement observed during drilling the shoe;
• Successful FIT: FIT to 2.40sg equivalent performed at the shoe,
• Drill to reservoir: Having a good cement in the shoe allowed to
successfully drill into the reservoir section with high MW
• Full exposure across reservoir: Exposing the full VIII horizon
with rich condensate reservoir
01
02
Post-Job:
Successful
Execution
Post-job: Successful execution

12. 12
31 October – 2 November 2018
Astana, Kazakhstan
 The key success factors in mitigating risks, such as stuck pipe and loss circulation, involved comprehensive
practical solutions for managing the ECD within limits by using different MWs, lower MW for under
reaming/liner cementing and high MW for casing running.
 The practical solution helped to well isolate challenging VII horizon resulting in significant improvement in
well delivery and reduced the risks despite having underbalanced conditions during under-
reaming/cementing.
 Finally, having good cement in the shoe allowed to successfully drill into the reservoir section with high
MW accomplishing successful completion of the well without any major problems previously occurring.
Therefore, this approach not only reduced the time, cost and also helped to deliver the quality wellbore.
How this can be of benefit to a practicing engineer:
 The case study of liner cementing at underbalanced condition provides a useful insights of how
unconventional techniques can be successfully implemented to achieve the overall accomplishment in
the well delivery performance.
Conclusion

13. 13
31 October – 2 November 2018
Astana, Kazakhstan
We are grateful to the management, SOCAR AQS LLC for permission to
publish this paper. Also, we would like to thank for all parties attended in the
planning and execution of these operation.
Acknowledgements

14. 14
31 October – 2 November 2018
Astana, Kazakhstan
• Buryakovsky, L. (2001). Petroleum Geology of the South Caspian Basin.
Baku Azerbaijan: Gulf Professional Publishing.
• Ulmishek, G. F. (2005). Petroleum Geology and Resources of the Middle
Caspian Basin, Former Soviet Union. Houston: U.S. Geological Survey
Department.
• SOCAR-AQS Lesson Learned database
References

15. 15
31 October – 2 November 2018
Astana, Kazakhstan
Thank you!