Replacing oil-based with water-based drilling fluids

摘要

An extended-reach well was planned and successfully drilled in the North Sea Central Graben with a water-based drilling fluid in an area where wells have historically been drilled with mineral oil-based and ester-based drilling fluids. Water-based drilling fluids were used because of the high costs of shipping cuttings drilled with inverts to shore for processing and disposal, coupled with the potential shutdown of drilling operations in times of bad weather when cuttings could not be transferred from the rig to supply vessels. These issues are especially important in the large-diameter hole section where high amounts of cuttings are generated.