Abstract: Compared with main producing series of strata,non-essential series of strata,with the characteristics of small oil - bearing area,thin thickness,low degree of superposition and etc,can not be taken as the key targets in well pattern adjustment in early stage of oilfield development.However, when the old oilfield entered the late development stage with ultra-high water cut,the role and significance of non- essential series of strata become increasingly prominent and therefore,the development focus is shifted.Taking non-essential series of strata as the main research object,this paper puts forward different development strategies for different types of non-essential series of strata based on classification and evaluation.The practical experience indicates good development effects can be achieved if there is a better understanding of geological characteristics and proper measures taken on the other hand,which provides guidance for other reservoirs of the similar kind.