Abstract: 3-D and 4-D (or time-lapse) seismic are important exploration techniques for field evaluation and development phase. Increasingly, time-lapse seismic is becoming a most popular tool for reservoir development and management. However, its application is constrained by reservoir conditions, production mechanism, non-repeatability noise in time-lapse seismic, and even the availability of basic 3-D seismic survey. This constrains the application of time-lapse seismic in onshore fields. Therefore, a 3.5-D seismic technique was proposed. The high quality 3-D seismic data obtained in the middle and later stage for reservoir development is used in the technique, combined with the production history to solve the problems in reservoir development and identify the distribution of residual hydrocarbon. The application to an onshore field in West China shows that 3.5-D seismic can effectively solve the problems in reservoir development, identify the distribution of residual hydrocarbon, and overcome the problem of the shortage of 3-D seismic or the impact of non-repeatability noise in the early stage of field. At the same time, the technique can decrease the risk of time-lapse exploration and improve the economic benefit of reservoir development.