Drilling Fluids and Solids Control Technology
Core drilling, expanding drilling (reaming) and non-core drilling were the main drilling methods employed for CCSD-1 Well. Different drilling methods needed drilling fluids with different performances to ensure implementation of the drilling technologies. Roller bit was employed for expanding drilling and non-core drilling with bigger debris granule (2–5 mm) produced while diamond bit was employed for core drilling with very fine debris (5–100 μm) produced. Rotary table drive with low rotation speed of 30–60 r/min was employed for non-core drilling and expanding drilling while downhole PDM and hydro-hammer with high rotation speed of 160–200 r/min were employed for core drilling. The pump capacity of drilling fluid was 25–35 L per second for non-core drilling and 9–11 L per second for core drilling. So, discrepancy was a little wide for the performance requirements of drilling fluid to different kinds of drilling methods. Carrying capability of mud was required to be good to clean away bigger debris granule produced in non-core drilling and expanding drilling, and then improve drilling efficiency finally, while core drilling required mud with the performance of not only be good at carrying, but also suspending debris while circulation was stopped, what’s more, the requirement of driving medium as a bottom power system should be satisfied. Simple for preparation, easy regulation of performance and convenient management were all required for drilling fluid in consideration of field preparation and management. For saving cost and reducing discharge, it was best to use a single drilling fluid system at drilling field, thus when drilling technology changed, the requirement of the changed drilling technology could be satisfied without changing drilling fluid system but with only simple regulation of its performance. The LBM-SD drilling fluid system specially designed for CCSD-1 Well was employed to accomplish core drilling, expanding drilling and non-core drilling.