Abstract: This paper draws inspiration from analyzing the exploration progress in mid-small sized peripheral basins in recent years: firstly, the exploration results obtained have exceeded what expected, and peripheral basins are expected to turn into tangible domains for increasing reserves; secondly, deeply trapped petroleum generative sags are the most favorable exploration areas; thirdly, whether to discover large and medium sized oil and gas fields is critical to realize exploration peak and sustainable development; fourthly, technological progress assures the achievement of exploration breakthroughs importantly. On the basis of correlation of the maximum reservoir size and the resource abundance and scale of 21 sags of 8 mid-small sized basins with higher exploration degree, this paper sets the evaluating selection criteria of peripheral basins, carries on evaluating selection and exploration potential analysis of PetroChina's 21 peripheral basins, and confirms 6 Class-I basins and 8 Class-II basins with broad exploration prospect. On that basis, this paper conducts study on development strategy of mid-small sized peripheral basins, and proposes that exploration turn into deeply trapped sags from high structures at four levels.

Key words: mid-small sized basin, exploration progress, target selection, exploration strategy