Drilling Engineering Design and Construction of Well Dong 11

The planned depth of well Dong 11 is 5,780 m, many complicated conditions may exist in the drilling process of this well, such as loose cementation and high risk of hole collapse in the upper formation, leakage of Cretaceous strata, caving mudstone in Jurassic, possible high-pressured saltwater zone and hydrocarbon zone in Sangonghe formation. In addition, this block is located in fault ruptured zone. Based on the above problems, casing program design, BHA design, drill bit selection, drilling fluid design and the cementing design was optimized and the drilling engineering design and site construction of the well was introduced. No complicated condition occurred during the whole well construction. PDC bit was used in the upper well section and PDC bit combined with screw drilling technology was used in lower well section, the average rate of penetration is 4.77 m/h, compared with the offset wells, the drilling speed increased obviously and the good hole diameter validates the serviceability of a strong inhibitive heat-resisting plugging polymer anti-collapse drilling fluid system in this area.