Steam flooding has been a matured method for developing heavy oil reservoirs and the ultimate recovery factor may reach 50%～60%. Many years of steam flooding practice indicates that reservoir geology is closely related to steam flooding performance. This paper analyzes the problems existing in steam flooding process,generalizes the influence of reservoir geology on steam flooding,and puts forward effective solutions which have alleviated the problems after field implement and improved steam flooding response. The study of geological factors mainly depends on geological analysis for coring well,geological structure,heterogeneity,oil reservoir,interbeds,and performance data. The mechanism of steam flooding is analyzed to determine steam sweep direction and to find out the geological factors affecting steam flooding.

Lianhua reservoir in Block Qi40 was developed by cyclic steam stimulation since 1987.By the end of 2005,the ratio of total oil produced to OOIP was 30.3%,the decline rate of the block was 13.3%.It is imperative to convert development scheme.The feasibility of steam flooding is studied for Block Qi40.The result shows that Block Qi40 is suitable to steam flooding,the recovery factor may improve by 24.58%～26.9%(theoretical value);according to the result of reservoir engineering,with present pattern,steam flooding has been conducted in reservoirs of LianⅠand Ⅱ2 and one more in the edge.Steam flooding parameters are optimized.Totally 139 well groups are deployed,with predicted ratio of total oil produced in the stage of 22.93%,and the recovery factor of cyclic steam stimulation + steam flooding of 51.9%.By the end of 2006,65 well groups had converted to steam flooding in the block and attained initial result.