Study and application of reservoir protection and anti-sloughing drilling fluid for Gao44-P2 horizontal well

Solid-free composite organic salt drilling fluid was used to protect the reservoir and prevent caving in Gao44-P2 well in accordance with the geological characteristics and drilling requirements.This drilling fluid system has high ratio of yield point to plastic viscosity(≥0.8),good lubricity,is highly inhibitive and reservoir-protective,especially appropriate for horizontal wells.It was applied in Gao44-P2 for drilling 400～2 931 m and horizontal section 2 542～2 931 m,including formations such as Minghuazhen,Guantao,Dongying and Shahejie,with horizontal displacement reaching 1 183.47 m.In the whole drilling course,the drilling fluid had shown steady performance,good sand carrying ability and borehole wall stability,no caving occurred,and no obstructions were encountered during tripping in and out,electrical logging or casing installation,thereby satisfied the requirements of drilling operation and reservoir protection.