Study Of Multi-scale Profile Control Technology In Low-permeability Sandstone Reservoirs

Low permeability sandstone reservoir is characterized by low permeability,low porosity and small pore throat,but macropore and micro-fracture also exist.At the same time,the artificial fracture produced by reservoir hydraulic fracturing causes water channeling easily after water injection,and the effect of conventional profile control and water shutoff operations is poor.How to improve the effect of profile control and displacement in this kind of reservoir is of great significance to improve oil recovery in the middle and later stages of low permeability reservoir.Taking the Triassic ZW Chang 6 sandstone reservoir in the eastern Ordos Basin as an example,this paper proposes the multi-scale profile control and oil displacement idea.By means of study and classification of flow space in study area,the flow space is divided into three types of the Fracture,Middle-large pore and Micropore.Based on the flowing ability evaluation of flow space at different scales,profile control agent and surfactant system is optimized and evaluated for different flow space,and the formula of profile control and related injection parameters are obtained.Reasearch results showed that permeability ratio of water phase permeability for flow space at different scales was extremely high,which could reach times of 10~3~10~5.The pre-crosslinking gel particle was optimized for the Fractured to reduce permeability,for the Middle-large pore selecting weak gel system for deep profile control and flooding.Aiming at the oil displacement efficement and flowing ability of the Micro-pore,anion-nonionic surfactant flooding system with ultra-low interfacial tension was optimize.The parallel core experiments in different scales showed that the average oil displacement efficiency was increased by 25.9%and permeability radio of three types of flow space after profile control and flooding adjusting had been effectively controlled into lower than the times of 10~2.Besides,the application of multi-scale profile control and displacement technology in the ZW field Chang 6 reservior achieved an excellent effect of oil increasing and water content reduction preliminarily.Therefore,it is a reliable approach for multi-scale profile control technology in low permeability reservoirs to improve oil recovery and shows a good development prospects.