Abstract: Study on the structural characteristics of transtensional faults and their controls on hydrocarbon accumulation is of great significance to the fine reservoir evaluation in the highly-explored areas of eastern China.The genetic model of transtensional faults in the Dongying Depression,Bohai Bay Basin,was studied,and the accumulation model controlled by transtensional faults in this area was established,on the basis of the geometrical and evolutionary characteristics of the transtensional faults.Research shows that,the transtensional faults in the Dongying Depression can be divided into three types,the broom-shaped,en echelon and juxtaposition faults.The broom-shaped transtensional faults are characterized by early extension and later transformation,with the structural style evolving from a single fault to a broom-shaped fault zone.While the juxtaposition transtensional faults feature early transformation and later extension,with its structural style evolving from the en echelon to the juxtaposition type.The en echelon transtensional faults are characterized by simultaneous transformation and extension,with its structural style evolving from a single fault at early stages to the en echelon fault zone.The differential evolution of transtensional faults leads to the model of controls over hydrocarbon accumulation with open-close coupling,providing a guidance for the fine exploration and development of reservoirs in transtensional basins.

Key words: tectonic evolution, genetic model, control over hydrocarbon accumulation, transtensional fault, Dongying Depression, Bohai Bay Basin