Abstract: Directional wells and horizontal wells in Bohai M Oilfield showed two completely opposite phenomena：a decrease in liquid production and an increase in liquid production after amplifying the production pressure difference. Research methods such as X-ray diffraction and scanning electron microscopy indicate that the reservoir is loosely cemented,the content of clay minerals is high,the pore throat distribution is slightly rough,and the sorting is better. Laboratory core velocity-sensitivity experiments show that the migration of particles is obvious,and the permeability increases with the increase of flow velocity,which is inconsistent with the phenomenon of decrease in liquid production of directional wells in actual production. In response to this problem,a seepage model of “long-distance migration and blockage near wells” is proposed,and the concept of velocity-sensitive clogging coefficient is introduced,which correlates the change of seepage velocity with permeability. By means of steady seepage theory,the velocity,permeability and formation pressure distribution of directional wells and horizontal wells are deduced. The reasons for the different production performances of the two well types are explained from the perspective of seepage mechanism,which provides an important support for the efficient development of Bohai M Oilfield.

Key words: Bohai Oilfield, particle migration, seepage mechanism, horizontal well, speed sensitive