Study On Gas Injection Development Mode Of Low Density And Compact Reservoir In L3 Block

China has abundant oil and gas resources of low permeability, it has been proven that low permeability tight oil geological reserves has amounted to more than70million tons at present. The exploitation of tight oil is significant to relieve the energy supply in our country. However, because low permeability oilfield has characters of low porosity, low permeability, low natural capacity and poor reservoir property and so on, the oil recovery rate of natural depletion is not more than5%. The effect of water flooding development is also poor due to the high heterogeneity, limiting the oil recovery rate to only about20%generally. In order to improve the oil recovery rate of low permeability tight oil reservoirs, it is urgent to study a new exploitation method. A large number of domestic and foreign research results show that injecting CO2to exploit low permeability tight oil is an effective method to improve the oil recovery rate. At the same time, the use of CO2can also reduce the greenhouse effect. The protection of the environment is also of great importance. CO2Hooding has gradually become a new technology to improve the oil recovery rate of tight oil, heavy oil and so forth, with good prospects for development.The L3block tight oil in the middle of Sichuan basin has low porosity, super-low porosity, ultra-low permeability and high pressure characteristics. What’s more, the reservoir type is fractured and fractured-porous. It has strong reservoir heterogeneity. And according to natural depletion and water flooding, the development effect is not ideal. It has difficulties to explore this block. But the field has considerable geological reserves. It is necessary to conduct an exploratory study of injecting CO2to enhance oil recovery.This paper studies CO2flooding of low permeability tight oil in L3oil block, using numerical simulation and indoor experiment. Under simulated reservoir conditions, formation oil PVT characteristics are measured by laboratory experiments, including the flash experiment, constant composition expansion experiment, the differential liberation experiment and gas injection expansion experiment. Finally, the formation fluid parameters and the phase variation rules after injecting CO2are attained. Using phase behavior simulation software matches the PVT experiments and expansion experiments, obtaining pseudo-component characteristic parameters of formation fluid, which are used in the follow-up numerical simulation of gas injection study. Meanwhile, on the basis of phase match, using the tubule experiment and the empirical formula obtains the minimum miscibility pressure of L3block formation fluid.According to the layer characteristics and the development situation of L3block reservoir, the geological model and numerical simulation model are established to study the CO2flooding development effect, mainly including well pattern, well spacing, CO2gas injection rate and so on. Final recommendation project is as follows:the injection rate is6000m3/d, with a rectangular five-spot pattern exploitation and well space is450m. After simulation development10years, the oil recovery can reach42.25%, which is15%higher than water flooding, significantly increasing the recovery rate. So it is feasible to inject CO2to explore the L3block tight oil. This paper recommended plan has been adopted to the field that is ready to conduct the CO2flooding pilot test work. The research result has a guiding significance to similar low permeability tight reservoirs.