Abstract: The Xishanyao formation in Cai?9 well block of Cainan oilfield in Junggar basin is a low?porosity and ultra?low permeability sandstone reservoir, which is now faced with cessation of production and to be abandoned due to its high water cut and very low production. This paper studied its percolation feature and remained oil distribution, and then proposed the adjustment system for infill injectors in inter?well remaining?oil enrichment zones in order to decrease the injector?producer spacing, increase the ratio of injection?production wells and improve reserves producing degree, and obvious successful effects have been obtained in such pilot testing well groups in this reservoir. It provides technical support and ideas for rest reservoirs adjustment and development in this area