Construction practice of ground subsidence monitoring drilling in the Yellow River Delta

Abstract:

The Yellow River Delta is a typical area of continental shelf sedimentation under the interaction of land and sea， with a majority of sand and mudstone layers， poor stratigraphic cementation， and frequent interbedding of mud and sand. In the drilling construction for ground subsidence monitoring， technical problems such as mud making in mudstone formations， water inflow in sand layers， leakage， dilution of mud， over diameter， and risk of hole wall collapse often occur. At the same time， the original state of the rock core should be maintained. In response to the technical difficulties， key technical methods such as cross caliber wireline core drilling tools， potassium based low solid polymer flushing fluid system， and water pressure coring were adopted， while also ensuring solid phase control and short lifting. Cement sealing is used to ensure the sealing effect and safety of the sealing operation. Oil well cementing and water reducing agent are used to significantly increase the fluidity of the cement slurry and reduce the probability of sealing accidents without changing the water cement ratio. The successful completion of this drilling provides a reference for similar core drilling in sedimentary formations in coastal areas in the future.