Experimental Research On Flow Control With Delayed Cross-linked Gel Of Fractured Low Permeability Reservoir

Fractured low permeability reservoir has gradually become an important subsequent power in the development of oil and gas in China, water flooding is the only way to develop low permeability reservoir. During water flooding, injected water needs high pressure gradient which can be injected into formation due to the low reservoir permeability and poor water absorption ability. Once water injection pressure is higher than the opening pressure of fracture in reservoir, fracture width and length are increased, and there will be water breakthrough phenomenon. Thus, the oil well soon be flooded.Aimed at the problem, based on the Yanchang Eastern Oilfield for example, analyzing the macroscopic heterogeneity of reservoir characteristics and the development characteristics of micro-fracture of the fractured low permeability reservoir, heterogeneity and natural fracture of reservoir and artificial fracture of wells are the essential causes of water flooding.Experiment is launched to evaluate the performance of delayed cross-linked gel, which contains concentration of cross-linking agent, concentration of polymer, pH value, salinity and temperature. Result shows that delayed cross-linked gel can effectively solve the problem of water channel between oil and water wells in fractured low permeability reservoir. The idea and principle of flow control with multi-slug gel injection method are expounded. The method uses gel to plug water channel in order to improve the formation pressure gradient which can increase fluid velocity, production speed, sweep volume and oil displacement efficiency and oil recovery is improved. Displacement and movement laws of gel in different width fracture,features of gel plugging with different width fracture and laws of water flooding velocity influencing flow channel after gel breakthrough are study by launching flow control experiment with delayed cross-linked gel. Experimental results obtained in single andmultiple fracture experiments verify the feasibility of flow control with multi-slug gel injection method which show that show that multi-slug gel injection can improve the water flooding pressure gradient, and is superior to the single slug with gel continuous injection.Field experiment indicates that flow control with multi-slug gel injection method can control the water channel effectively and injection pressure of injection well rises significantly. 8 m3 water is injected in every injection well per-day and injection pressure can rise to 8.5 MPa.Average water cut of oil well decreases from more than 90% to 71.7%. Flow control with multi-slug gel injection method can solve the problem of water breakthrough in fractured low permeability reservoir effectively. The preliminary development effectiveness in this oil field can provide a good reference to the approximate reservoirs.