Overview on Drilling Operation of the WFSD-1 in Wenchuan Earthquake Fault Scientific Drilling Project

Abstract:

This paper introduces the drilling operation of the WFSD-1 of the Wenchuan earthquake fault scientific drilling (WFSD) project as well as the experience gained and lessons learned during the hole drilling. Some extreme technical difficulties in the drilling operation, such as hole gushing water, broken formation, borehole collapse and tight hole, were overcome. A mud system with low water loss, high density and good lubrication properties was put to use to resolve mud expansion in fault gouge and diameter shrinkage resulted by geostatic stress. A twohaves tube coring technique was used to remain core in undisturbed state even in broken formation.