|Authors||Abdullah Al-Ajmi (Kuwait Oil Company) | Abdulaziz Al-Rushoud (Kuwait Oil Company) | Ashis Gohain (Kuwait Oil Company) | Faiz I Khatib (Kuwait Oil Company) | Faisal Al-Naqa (Kuwait Oil Company) | Faisal Al-Mutawa (Kuwait Oil Company) | Majed Al-Gharib (Kuwait Oil Company) | Sudhir Birthariya (Kuwait Oil Company) | Ankit Mago (Kuwait Oil Company) | Alanoud Al-Mekhlef (Kuwait Oil Company) | Bader Al-Tarkeet (Kuwait Oil Company) | Yaqoub AlAli (Kuwait Oil Company) | Arnaldo Rossi (Newpark Drilling Fluids) | Dario D'Angelo (Newpark Drilling Fluids) | Nazareno Spagnoli (Newpark Drilling Fluids) | Fady Samaan (Newpark Drilling Fluids) | Praful Rane (Newpark Drilling Fluids) | Alberto Scolari (Newpark Drilling Fluids)|
|Publisher||Offshore Technology Conference|
|Source||Offshore Technology Conference Asia, 20-23 March, Kuala Lumpur, Malaysia|
Shale stability and differential sticking are the main challenges while drilling through shale and sand sequences. Conventional mud systems cannot always provide the required wellbore stability and sustained high overbalance, which has led to an increase in use of ‘customized fluids’.
Offset wells were reviewed to identify the issues while drilling this challenging trajectory through troublesome stressed Zubair shale and sand sequences. This review revealed serious well-bore instability, pack offs, differential stuck pipe leading to the loss of downhole tools and sidetrack operations.
Traditionally, oil-based mud (OBM) have been used while drilling these formations with high NPT hours. Due to necessity of comingling two sections in a single section, it was necessary to identify a fluid's solution, which can provide good borehole stability.
A customized drilling fluid system was designed by using deformable sealing polymer (DSP, deformable size) in conjunction with Synthetic Resilient Graphite and Sized Calcium Carbonate (CaCO3) in conventional OBM. These Nano particles effectively plug the pore throats and minimized the fluid invasion, which was confirmed by particle / permeability plugging tests under down hole conditions to overcome below challenges.
Improve hole stability through stressed shale formations
Minimize risk of differential stuck pipe across low pore pressure formations
Mitigate induced losses by utilizing unique wellbore-strengthening technique
Enhance hole-cleaning efficiency at critical angle
Drilling, logging, running and cementing liner was successfully completed in the commingle section without any incident. There was no NPT related to well-bore instability or differential sticking tendency reported. Very low torque and drag was observed in addition to enhanced well-bore cleaning in the high angle section.
This paper will present the success of the deformable sealing polymer in OBM utilized to comingle Upper Zubair shale and Ratawi shale with case histories for reference.