Enhancing drilling performance for surface sections across multi-layer formations is relatively challenging in the Middle East due to the carbonate's soft nature combined with interbedded formations resulting in lost circulation, harsh drilling environment leading to shock-and-vibration behaviors, and bit/BHA damage; factors including bit size and applied drilling parameters affect these conditions. This manuscript demonstrates the study and successful field application performed on different approaches, including bit/BHA selection, hydraulics enhancement, and drilling fluid recipe.
Firstly, by lowering Total Flow Area (TFA), hydraulics analysis demonstrated an increase of Horsepower per Square Inch (HSI) and Jet Impact Force (JIF) by up to ~28% compared to the existing current designs. Furthermore, the advantage of the partially hydrolyzed polyacrylamide (PHPA) additive for the Mix on Fly (MOF) recipe is valuable as a lubricant shale inhibitor, sealing microfractures and coating shale surfaces with films retarding dispersion and disintegration. Hence, reducing torque and friction and minimizing shock-and-vibration behaviors. The BHA was engineered and redesigned in order to increase WOB limits and reduce building tendency. Additionally, bit selection was accomplished from IADC 435x to IADC 425x to optimize the ROP and durability.
Improvement results have been observed while drilling the section in one run (shoe to shoe runs) without any wellbore instabilities and bit/BHA damages. The BHA has maintained the hole angle from deviation. For instance, the Gyro logs showed that the maximum inclination of the wellbore was less than ~1.5 degrees. Additionally, the BHA higher WOB was applied on thicker shale layers, indicating a higher performance once applying higher WOB. Ultimately, due to the PHPA additive on MoF, a smooth trip out of the hole illustrated that the hole was in good condition, eliminating the wellbore instability risks and the wiper trip.
Moreover, the shocks and vibrations were reduced considerably based on the nearby offset. In addition, a new record for enhanced drilling ROP of 43.83 FPH was achieved. Showing illustrated improvements with an increase of ~35% compared to offsets of 22in section across that formation interval. Indeed, TCI 425x bit established a higher durability during this drilling run with medium dull grading compared to 435x, where it had to POOH for bit damage. This led to reducing the section's time by 0.75 days compared to the operator's existing best performance time of the offset wells in that field.
This manuscript offers engineered key solutions to numerous challenges encountered across various surface sections relying on the well types while drilling with full circulation or lost circulation across the formation compositions such as but not limited to Anhydrite and Shale. The outcomes could be extended as lesson-learned for such challenges and easily implemented considering full risk assessment for drilling wells in the Middle East and Worldwide to illustrate similar advantages.