Research and Application of Key Technology of Directional Drilling for Hot Dry Rock
In order to promote the industrialization of hot dry rock in China,the first experimental development project of hot dry rock in Gonghe Basin of Qinghai,including one vertical well and two directional wells,was de-ployed by China Geological Survey.The key technologies of directional drilling are researched and applied in this paper.The hot dry rock in Gonghe Basin were mainly granite,with the characteristic of high hardness,strong abra-sive and high temperature,which was also affected by large-scale hydraulic fracturing,there are many technical problems with drilling operations such as low rate of penetration,short life of rock breaking tool,unstable signal of measuring instrument at high temperature,and big difficulty of well trajectory control.To ensure smooth drilling operation,the key technologies and equipment have been developed including high temperature wireless measuring while drilling instrument,high temperature polymer drilling fluid system,and spiral plate mud cooling equipment.The bottom hole assembly of roller bit,single camber mud motor and measuring while drilling was determined.The double target directional well was drilled safety and efficiently,with the target accuracy of 4.85 meters and 8.97 meters respectively,the drilling period reduced by 20％,the maximum footage of 175 meters and the maxi-mum rate of penetration of 3.74 m/h achieved.
hot dry rockdirectional drillinghigh temperature measure and control while drillingpolymer drilling fluiddrilling fluid cooling technology
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