Abstract: Steam assisted gravity drainage (SAGD) has been widely used in the exploitation of onshore heavy oil reservoirs in the Fengcheng Oilfield of Xinjiang Oilfield.However,due to high heterogeneity and low permeability of reservoirs,the preheating period of SAGD wells is long,resulting in high steam costs,making it difficult to treat the production fluids.Hence,the relative technologies have been put forward,including squeezing fluid and dilatancy in SAGD wells,and the reservoir stimulation prediction method.The three influencing factors on dilatancy effect (characterized as connectivity coefficient) were analyzed,i.e.petrophysical properties,reservoir geometric parameters and injection flow rate.Based on 92 finite element examples under the above three factors,an evaluation method for immediate prediction of injection and dilatancy effects in SAGD wells was proposed.The application of connectivity coefficient prediction chart in three SAGD wells in the Fengcheng Oilfield indicated that the shortening amplitude of the preheating period had a good positive correlation with the connectivity coefficient.The connectivity coefficient prediction chart has provided an efficient and rapid evaluation method for optimizing the injection pressure and flow rate and shortening the preheating period of SAGD wells in field operation.