Both the surface drainage and subsurface fault-block oil reservoirs in Subei (northern Jiangsu) oilfield are very complicated. The oilfield is typically composed of small

complex

and heterogeneous reservoirs. Exploration and development stages cannot be distinctly separated

due to the complicated geological and surface conditions.Therefore

a simultaneous exploration and development method has been introduced in this paper

i.e.the exploration be combined with the development

or a comprehensive arrangement should be made for the exploration and development research work and production

so that exploitation and evaluation can be done while exploring the oil reservoirs. The key techniques and methods include detailed 3D seismic interpretation early assessment of oil reservoirs

drilling and appraising of the key wells

closely combining multiple disciplines

conceptual designing

and programme demonstration and optimization. Implementing the simultaneous exploration and development method in Subei oilfield

many key techniques have been developed;at the same time

significant economic returns have also been achieved.As a result

both the increments of reserves and productivity are higher than any other periods before the “Eighth Five-Year Plan”.