Experimental Study On The Influence Factors And Oil Drive Characteristics Of Gas Injection Gravity Drainage

At present,the traditional water injection enhanced oil recovery method has problems such as difficult injection and low sweep coefficient,and the use of gas injection to enhance oil recovery can solve this problem well.Among them,the top gas injection assisted gravity drainage technology is an enhanced oil recovery method that combines the advantages of gas flooding and gravity flooding,and has good development prospects.Recognizing its displacement characteristics and oil displacement mechanism is the key.In this thesis,a thick oil reservoir in China is taken as the research object,and the experimental research of top gas injection gravity drainage is carried out by means of indoor physical simulation experiments.Firstly,through the gas displacement experiment of full-diameter long core and small core under the action of gravity,the optimal physical simulation experiment method of gravity gas flooding is clarified;based on the full-diameter core displacement experiment,the factors affecting the macroscopic oil displacement effect of gravity gas flooding are studied.,and clarified its main controlling factors,and screened out the best displacement parameters in the laboratory test;finally,the NMR scanning analysis method was used to study the pore-throat production boundary of the fluid in the process of gas injection gravity flooding,and to clarify the production characteristics of the microscopic fluid.It plays a theoretical guiding role in the development and application of gas injection gravity flooding oilfields.The results show that for the physical simulation method of gravity gas flooding,the full-diameter core can simulate the sweep effect under the action of gravity,and can simulate the displacement process more realistically.Full-diameter cores carry out research;core permeability,formation dip and injection pressure are positively correlated with the oil displacement effect of top gas injection gravity flooding,and the gas injection rate is directly related to the oil displacement effect of gravity flooding.The oil displacement effect has a negative correlation,and the importance of each factor on the recovery factor is ranked as follows: gas injection rate,reservoir permeability,reservoir dip angle,and displacement pressure;For the study of pore-throat production limits,it is found that the production capacity of high-speed top gas injection for sub-micron pores is stronger than that of low-speed and medium-speed top gas injection,and the lower the gas injection rate,the stronger the production capacity of micron-scale pores.High-speed gas injection is more capable of producing small pore throats at the top,while low-speed gas injection has a weaker ability to produce remaining oil in small pore throats at the bottom;The higher the injection pressure,the more uniform the production of the pore throats in the overall core.With the increase of the injection pressure,the remaining oil in the small pores is mainly produced further.