Abstract: In order to promote the integration of offshore exploration and development in Weixinan Sag of Beibuwan Basin, and solve such problems in the traditional drilling mode of “exploration well–evaluation well–development well–adjustment well”, as long evaluation times and production periods, high development economic threshold and proven and controlled geological reserves that are difficult to produce, drilling modes of development evaluation well was proposed. The modes included both the development mode and exploration mode. The development mode was based on the production platform to achieve rapid production and was divided into production platform drilling mode and development well project drilling or concurrent exploration mode. The exploration mode was aimed at evaluating the targets outside the production platform, determining the reserve scale, and avoiding development risk. The process was divided into rapid evaluation mode and concurrent exploration mode of rolling exploration well. The four drilling modes above have achieved remarkable application effect in 45 development evaluation wells in Weixinan Sag, of which 37 were drilled successfully with a success rate of 82%. The research result show that the proposed drilling modes can promote new proven reserves and the difficult-to-produce reserves, and effectively promote sustainable development of oilfields, with great guiding and referential significance in the exploration and development of mature areas.