Matching technology for optimized fast drilling of horizontal wells in Changqing Gasfield

Drilling of horizontal wells in Changqing Gasfield is characterized by complex formation conditions and poor rock drillability. To explore the matching technology for speeding up the horizontal well drilling in this area, the compound drilling technology, mud properties, prevention of backing pressure and preventing of complex conditions and accidents were applied in field drilling practices. The practices indicated that high efficiency polycrystalline diamond compact (PDC) bit and screw compound drilling can improve rate of penetration significantly and reduce well construction period. By controlling mud properties, the bentonite, polymer and sulphonated polymer drilling fluid systems can prevent the formation leakage and collapse at different intervals and can satisfy the lubrication requirement of drill string. Method of inverted drill string and application of hydraulic thruster can decrease frictional resistance of the drill string so as to mitigate backing pressure and improve ROP of slide drilling. Besides, plans to prevent complex conditions and accidents should be developed and executed strictly during drilling. This matching technology provides a reference for the horizontal well drilling with similar well structures in Changqing area, which is of great significance to improvement of exploration and development benefit.