Study on imbibition during the CO2 enhanced oil recovery in fractured tight sandstone reservoirs

Abstract

CO 2 enhanced oil recovery (CO 2 -EOR) is a key technology for improving the oil recovery of fractured tight reservoirs, and imbibition has been recognized as an important mechanism for oil recovery in low-permeability reservoirs. To clarify the imbibition role and influencing factors during the CO 2 -EOR process in fractured tight oil reservoirs and also improve the EOR mechanism, a high-temperature and high-pressure CO 2 imbibition experiment was performed based on the nuclear magnetic resonance technology. The results show that high pressure and high permeability are beneficial to imbibition efficiency. The salinity of the imbibition fluid is not very sensitive to the imbibition recovery. In addition, the CO 2 increases the imbibition speed and can also significantly improve the production rate and oil recovery. It is beneficial to increase the CO 2 concentration to shorten the imbibition equilibrium time and enhance oil recovery. According to the results of the nuclear magnetic resonance study, although the nanopore can provide a greater imbibition force, the oil flow resistance is also larger, but CO 2 can reduce the flow resistance of oil and be conducive to oil production in smaller pores. The inclusion of imbibition into the research category of CO 2 -EOR mechanism will be more in line with field practice and more scientific in fractured tight reservoirs, thus providing theoretical support for the development and improvement of the CO 2 -EOR technology.

Buoyancy-Driven Dissolution Instability in a Horizontal Hele-Shaw Cell

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Insight into the Imbibition Behavior of Low-Frequency Artificial Vibration Stimulation in Tight Sandstone

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“…With conventional oil and gas resources declining and the gap between the energy supply and demand growing, tight oil resources have become critical replacement to the sustainable growth of China’s oil industry. − Due to the low pressure of the reservoir, the production of horizontal wells declines rapidly under the natural driving energy, with an annual decline rate of 40–90%. Additionally, the one-time recovery rate is only 5–10% and more than 90% of the remaining oil is difficult to utilize effectively…”