Abstract:

Low permeability reservoirs are widely distributed in Subei（northern Jiangsu province） Basin. There are some problems such as insufficient natural energy and fragmented structures, which make it difficult to form an effective injection-production well pattern. Therefore, the effect of water injection is poor. The CO₂ huff and puff technology can effectively solve these problems with less investment, simple process and rapid results. Choosing the proper wells to execute is the key to the success of this technology. Based on the comparative analysis of CO₂ huff and puff in low permeability reservoirs in Subei Basin in recent years, combined with indoor physical simulation experiments and numerical simulation results, it is considered that closed reservoirs with medium-deep burial depth and fracture development are more suitable for CO₂ huff and puff. Fractures have a greater impact on huff and puff effect. There is an appropriate interval for formation pressure, not the bigger the better, whether miscibility can be achieved or not. It has no decisive effect on the throughput effect. Oil wells with high initial production and water cut of 30 %~70 % in lower structure are more conducive to huff and puff, and the huff and puff effect of horizontal wells is better than that of vertical wells.

Key words: low permeability, CO₂ huff and puff, formation pressure, effect of fractures, horizontal well