Application of Underbalanced Foam Drilling Fluid in Long-14 Well

The well of Long-14 was a major exploration well for the structure of Ku Long-shan in Qingxi oilfield.The foam fluid was employed for underbalanced drilling in the section from 1358 m to 2670 m.The available additives and the optimized formulation were determined by a great quantity of laboratory experiments.The data from evaluation tests indicated that the optimized foam fluid exhibited favorable foamability,temperature resistance,contamination protection and inhibition and had a long stability period and a slight corrosiveness.The field trials demonstrated that the foam fluid developed met the requirement of cuttings carrying for the air drilling and can still maintain the hole stability even if continuous water production was encountered.No caving occurred.