The Technology Research Of Displacement System Expanding Swept Volume In The Low-permeability Field

Low-permeability resources occupies an important position in reservoirs in China. With increasing in exploration and demanding for petroleum resources, low-permeability reservoirs has become an important target of exploration and development in the future in China. However, relative to middle and high permeability reservoirs, the low-permeability reservoir in general has characteristics of deficient natural energy, complex pore structure, serious cementation and poor connectivity. At the same time, it has much and small throat which is hardly to connected with pores and even has some of the unconnected pores, so fluid flowed in low-permeability reservoir has larger resistance and lower movable fluid saturation. Therefore, that exploit low-permeability reservoir using natural consumption is not only low production and rapid formation pressure drops, but also low recovery. Furthermore, exploitation using artificial way to keep pressure exists problems of injecting water hardly and gas channeling when injecting gas, so the development effect is not good.In order to make low-permeability reservoir develop and utilize effectively and aiming at the problems of viscous fingering and channeling in the process of injecting gas, this paper analyzed the effect of pore structure, pore throat distributions, movable fluid saturation and clay content of the low-permeability reservoir on reservoir development, carried out gas drive/active water drop injection experiments to change the flow resistance and gas drive/foaming agent drop injection experiments to expand the swept volume. The experimental results show that active water drop injection in the process of gas drive can increase flow resistance and improve the phenomena of viscous fingering and channeling in the development process of low permeability reservoir. Utilizing foam properities which is stability contacted with water and anti-foaming contacted with oil, foaming agent drop injection in the process of gas drive can form foam system and block large pores which have lower oil saturation, those will lead to subsequent injected fluid into small pores which have higher oil saturation. Therefore, it will expand swept volume, and activate, integrate and displace residual oil in the small pores to increase oil production and improve oil recovery.