Abstract: The target layer of the Y1 oil and gas field  is deeply buried, with a large dip angle and a typical low porosity and permeability reservoir, there are some difficult problems, such as difficult to release Rop in surface layer, prominent problem of borehole instability in middle and upper layer, poor drill ability in deep layer, low local formation loss pressure and high risk of loss during cementing in long open hole section, etc. , the drilling speed and efficiency of the gas field are restricted. To this end, the corresponding comprehensive technical research, through the analysis of the gas field during the operation of the technical difficulties encountered, and the East China Sea has a mature drilling technology system, key Technologies, such as casing program simplification, oil-based mud system, personalized PDC bit design, and optimized BHA, have been developed to speed up drilling operations in deep and ultra-deep wells in the Y1 oil and gas field, the technical problems which restrict drilling speed and efficiency are solved, and the technical guidance is provided for the scale development of the gas field.

Key words: Lost Circulation, wellbore instability; casing program, BHA