Abstract: Reservoir in Yi491 block in Bonan oilfield has poor poroperm characteristics and strong heterogeneity, thus development is very difficult. Based on experiences a-chieved in development of Bonan low permeability oilfield and in view of reservoir characteristics, several development technologies are applied, such as small well spacing,putting pay zones into production layer - by - layer upward and early water injection. Reservoir damage and rapid increase of water cut in response oil wells are thoroughly studied. Hydraulic fracturing, acidization with composite acid, repeat reperforating and unsteady water injection are carried out to tap the production potential of reservoirs. Water cut is effectively controlled and oil production is effectively stabilized, realizing highly effective development of Yi 941 block.