Aiming at the demanding requirements of sealing performance in ultra⁃deep oil and gas wells, a double main sealing structure consisting of conical surface to conical surface and cylindrical surface to spherical surface was designed based on the special thread sealing mechanism. Using numerical simulation method, the changes of contact stress and the contact length of the sealing surface under the four conditions of tensile, compression, tension and internal pressure, tension and internal and external pressures were analyzed. The sealing performance of threaded joints under the ultimate load was studied, and the change rule of sealing capacity with different loads was obtained. The full⁃scale test results show that the sealing performance of the double main seal premium threaded joint meets the application requirements.

Since the implementation of SP Flooding in Jin 16 block of Liaohe oilfield, there are still some problems existing in some injection wells. For example, the monolayer liquid absorption amount is too large and front advance velocity in each layer is not uniform, which resulted in the faster rising of polymer concentration in production wells. In order to evaluate the SP flooding effect of different size slug combination with equimobility, SP flooding experiments were conductedusing homogeneous and heterogeneity core. The results showed that the oil recovery of Equimobility Displacement method was 3.54% higher than the conventional single slug SP flooding when the polymer and surfactant were used with the same dosage. Equimobility the diversion rate of the medium and low permeability layer can be obviously improved when the displacement method was uesd. Conversely, the high permeability layer was reduced. Therefore, a reasonable combination of different size equimobility SP slug can effectively improve the oil recovery efficiency of the heterogeneous core.