SLIM HOLE WELL CONSTRUCTION METHOD Russian patent published in 2010 - IPC E21B7/20 E21B43/00 

FIELD: oil and gas industry.

SUBSTANCE: there performed is borehole sinking, lowering and attachment of casing and production strings. The first part of the well bore - direction is drilled with diametre of not more than 300 mm, the second part - conductor is drilled with diametre of not more than 220 mm, the third part is drilled with diametre of not more than 160 mm. As drilling solution during drilling of the direction, there used is clay solution with density of 1.12-1.20 kg/m³, during drilling of conductor and the main bore - service water with density of 1.00-1.09 kg/m³. Flow rate of service water is determined with lost circulation zones exceeding the service water absorption. Opening of production interval is performed by using service water with addition of mixture of surface-active substances, "МЛ-81 Б" grade, in quantity of 1-3%. After drilling the well bore from the bottomhole to the mouth, or in case of lost circulation zone, to lost circulation zone, is filled with clay solution with density of 1.12-1.20 kg/m³. Logging investigations are performed. Drilling installation is lowered, water service is pumped and the productive formation interval is passed by means of rotary bit for 2-4 times with speed of 20-30 m/hour. As production string there used is string with outer diametre providing the thickness of cement sheath wall of not less than 16 mm.

EFFECT: reducing the costs of well construction.

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