Integration of 1D Geomechanics Modeling and High-Performance Water-Based Mud HPWBM System Design, Improving Cost-Effective Drilling of High-Angle Wells Through Cauvery Shale Sequence: A Case Study from Cauvery Basin, Offshore India
- Sankhajit Saha (Baker Hughes, a GE company) | Bhuwan Chandra Gariya (Hindustan Oil Exploration Company Ltd) | Debabrata Panda (Hindustan Oil Exploration Company Ltd) | Satya Perumalla (Baker Hughes, a GE company) | Tuhin Podder (Baker Hughes, a GE company) | Shrikant Thanvi (Baker Hughes, a GE company) | Chandrashekhar Deshpande (Baker Hughes, a GE company)
- Document ID
- Society of Petroleum Engineers
- SPE Oil and Gas India Conference and Exhibition, 9-11 April, Mumbai, India
- Publication Date
- Document Type
- Conference Paper
- 2019. Society of Petroleum Engineers
- 7.2.1 Risk, Uncertainty and Risk Assessment, 2 Well completion, 1.11 Drilling Fluids and Materials, 1.12.2 Logging While Drilling, 0.2 Wellbore Design, 1.12.3 Mud logging / Surface Measurements, 1.12 Drilling Measurement, Data Acquisition and Automation, 7 Management and Information, 2.3 Completion Monitoring Systems/Intelligent Wells, 0.2.2 Geomechanics, 5.1.2 Faults and Fracture Characterisation, 7.2 Risk Management and Decision-Making, 5.1.5 Geologic Modeling, 1.6 Drilling Operations, 1.8 Formation Damage
- Cost-effective drilling, High Angle Wells, 1D Geomechanical Modeling, High-Performance Water Based Mud, Enviromental impact factor
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Drilling through the thick shale sequence (Oligocene to Paleocene age) of Cauvery offshore showed severe wellbore instability in the past due to incompatible mud program that increased overall operational cost. While new high-angle sidetrack development wells had been planned, three major challenges need to be addressed. First, proper mud weight recommendation for preventing mechanical instability; second, introduction of a cost-effective mud system preventing time-sensitive failure; and finally, mitigating the environmental impact factor of the mud system.
Geomechanical modelling and Hole Stability analysis had been performed based on available dataset. An optimized mud weight (MW) program was developed based on the analysis. Considering the time-dependent failure characteristics of the shale and overall cost effectiveness, just modifying the mud weight does not address all of the challenges delineated above. Consequently, special "high-performance water-based mud system (HPWBM)" was designed instead of oil-based mud (OBM). This HPWBM was formulated based on the nature of shales encountered. While drilling, real-time geomechanics further facilitated controlled drilling conditions and optimized the mud program.
The well-based geomechanical model indicated a hydrostatic pore pressure gradient in the region. The relative magnitude of three principle stresses showed a normal fault stress regime and maximum horizontal stress (SHmax) azimuth appeared to be nearly aligned to the N-S direction. Hole Stability analysis showed that a minimum of 12 ppg mud weight was required to drill the 8½" section. The sidetrack holes had a maximum inclination of 75 to 77 degrees. Different polymers and bridging agents were added to prepare the customized HPWBM in order to address shale instability and formation damage due to overbalance. Real-time monitoring during drilling operation utilized logging while drilling (LWD) log data, drilling parameters and mud logging data to promote smooth drilling operations. Through systematic planning and execution, the high-angle sidetrack holes had been drilled with zero non-productive time (NPT) in terms of well bore stability. More than 50% cost reduction was achieved on the mud system.
An integrated solution that includes pre-drill geomechanics, HPWBM system design and real-time well monitoring helped to reduce the risks due to model uncertainties while drilling high angle wells through the thick shale section. This approach helped to reduce significant operational cost with an improved success rate.
|File Size||1 MB||Number of Pages||14|