Minimize drilling time for Mexico land well
PEMEX was constructing 12 1/4-in hole sections of land wells in interbedded formations of 10,000 to 30,000 psi in Mexico's Mesozoic Chiapas-Tabasco oil province. The operation required drilling the 13 3/8-in casing shoe track at approximately 3,800-m MD, kicking off from vertical, building inclination to 18°, and holding the tangent to section TD at more than 5,200-m MD. PEMEX typically spent 66 days and made six BHA trips for bit changes for this type of operation and wanted to reduce both drilling time and the number of BHA trips.
Combine turbodrill with hybrid bit
Schlumberger combined a 9 1/2-in steerable Neyrfor Traditional turbodrill with a 12 1/4-in Kinetic hybrid diamond-impregnated bit from Smith Bits, a Schlumberger company. The turbodrill provided the precise toolface control needed to drill the planned trajectory, and the diamond-impregnated bit provided effective cutting action for drilling out the shoe track and maintaining a high ROP in a mix of lithologies that included mudstone, marl, shale, wackestone, and an anticipated 30% chert.
Using the turbodrill, drill bit, and 14.6-lbm/galUS oil-base mud, inclination was built from vertical to 18.2° in just 136 m, and the 12 1/4-in hole section was drilled to planned TD at 5,255-m MD in just four runs totaling 1,455 m. Circulating time totaled 1,073 h, of which 861.75 h was on-bottom drilling time. ROP averaged 1.7 m/h and could have been higher if rig capability had not limited the flow rate to 518 galUS/min and standpipe pressure to 4,100 psi.