Method for selecting gas injection displacement transfer point of compact oil reservoir

Abstract

The invention relates to a method for selecting a gas injection displacement transfer point of a compact oil reservoir, and belongs to the technical field of oil and gas exploitation. The method specifically comprises the following steps: CO2 is used as displacement gas, and the gas injection speed V is optimized through a long core oil displacement experiment; the minimum mixed phase pressure P1of CO2 is measured through a slim tube experiment; before phase mixing is simulated, near phase mixing and phase mixing displacement are simulated, and initial gas injection pressure P is optimized; agas injection quantity nPV during CO2 breakthrough is determined through the long core oil displacement experiment; and a first-stage CO2 injection quantity is optimized through a two-stage long coreoil displacement experiment. According to the method, the best nitrogen injection time is selected through a series of long core oil displacement experiments, and nitrogen injection is performed at the time to drive oil, so that a high oil reservoir recovery rate can be obtained and economic benefits can be improved.

Description

technical field [0001] The invention belongs to the technical field of oil and gas exploitation, and in particular relates to a method for selecting gas injection displacement transfer points in tight oil reservoirs. Background technique [0002] In the process of oil and gas exploration and development, due to the poor physical properties and water sensitivity of tight oil reservoirs, it is difficult to inject water, the formation energy is insufficient, the production declines rapidly, and the recovery factor is low. With the gradual deterioration of undeveloped oil and gas resources, the unique advantages of gas flooding EOR technology will become more and more obvious, with huge application potential and broad prospects. [0003] At present, gas injection EOR technologies mainly include: CO2 flooding, air flooding, nitrogen flooding, hydrocarbon gas flooding, and flue gas flooding. CO2 is currently regarded as the best injection gas, but CO2 often acts in large pores, a...

AI Technical Summary

Problems solved by technology

CO2 is currently regarded as the best injection gas, but CO2 often acts in large pores, and the sweep efficiency is low and gas channeling is easy to occur, and the breakthrough time is early.

N2 can be used as nitrogen to maintain the formation pressure. After being injected into the formation, it has a certain elastic potential energy. Its energy release can play a good role in gas lift and drainage, and it is economical. However, the oil displacement efficiency is not as good as that of CO2. Therefore, the advantages of the two can be combined. Choose different injection-production methods at different stages to improve recovery and economic benefits, such as patent CN201810104415.1, which introduces a method of using nitrogen to assist carbon dioxide huff and puff to recover tight oil. First, CO2 is used to soak the well and then carry out one-stage displacement , and then sequentially inject nitrogen and CO2 into the well, and then use nitrogen and CO2 to displace the crude oil

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