Study And Application Of Stable Production Technology Through Deep Flooding In Redevelopment Of Block Shen-67

In the phase of high water cut development of sandstone reservoir, deep flooding technology is one of the major measures to improve waterflooding effect and enhance oil recovery, which plays an more and more important role at oilfield flood development later stage. This technology, by injecting chemical agents which can realize water-plugging and profile control function in deep reservoir, adjust flow direction to enlarge swept volume in order to displace residual oil.This article, combining with development characteristics and contradiction, chooses northeast of Block Shen-67 as a pilot area for deep flooding. The pilot area with perfect flooding pattern, whose oil-bearing area is 0.86 square kilometer, holds recoverable reserves 4.274 million tons, and its recovery percentage of OOIP is 29.8%, waterflooding reserves produced degree is 82%, and target zone is S32IV whose average measured porosity is 19.5%, mean permeability is 374×10-3 m2, permeability max-min ratio is between 4 and 170, and permeability variation coefficient is between 0.9 and 0.9. Reservoir temperature of the pilot area is between 65 and 70 degree Celsius, which is suitable for deep flooding.According to the reservoir characteristics of Block Shen-67, researchers determined the injection technology of deep flooding-"Water plugging comes first before deep profile control and oil displacement". Through study on polymer gel system properties together with indoor lab core simulating test, it has been determined that polymer gel system for profile control whose formula is 0.3-0.5% composite polymer plus 0.3-0.5% cross-linker and weak gel system whose formula is 0.15-0.2% composite polymer plus 0.3% cross-linker when core permeability is between 150×103 m2 and 3500×10-3 m2. In the process of application, gel and weak gel systems with additives of 0.1-0.5% pre-crosslinked expended granular particle have been applied considering improving profile control and water shutoff effect towards water injectors which hold dominant channels of waterflooding. Coreflooding simulation test demonstrates that oil recovery could be improved 17%～22% by utilizing composite polymer weak gel system. In consideration of characteristics of reservoir such as pores and throats of formation etc., polymer micro-micelle oil displacement system has been determined, injecting 3 flooding slugs whose volume should be 0.2PV, and its water-plugging rate reaches 92% and the system can improve oil recovery 11% or more to meet the demand to enhance oil recovery by chemical flooding.During 2012～2014, field experiments had been carried out in 9 symmetry elements, which demonstrated that deep flooding can effectively enlarge swept volume, slow down natural decline and realize the target of stabilizing oil production and controlling water cut.