Ultra-deep wells in fractured-vuggy reservoir nitrogen injection EOR technology

Tahe carbonate reservoir shows strong heterogeneity. The cavern is the primary reservoir space while fracture is mainly plays a role of connecting channel in this reservoir. The fluids in reservoir are mainly taking the form of pipe flow model. Complex reservoir type lead to the remaining oil distribution is unclear and early development mainly relies on elastic drive and water flooding with low recovery efficiency in this oilfield. At present, this fractured-vuggy reservoir within later stage of water flooding faces the difficulties of potential tapping and remaining oil reserves difficult to use, and nitrogen injection for oil flooding process provides an ideas and methods to solve this problem. Through injecting gas source selection, optimization of injection process on the ground and wellhead and string optimization, the technique successful realizes the gas-water mixed injection pressure decreasing technology and multi-turn gas injection and machine pumping switching. The implementation of this technology saves the cost, and improves production efficiency and reduces the safety risk. The research provides a new idea and method for gas injection enhancing oil recovery efficiency of carbonate reservoir.