Study On Well Selection Method And Limit Cycles Of CO₂ Huff And Puff Yechnology In Nanpu Land Shallow Reservoir

The Nanpu land shallow reservoir is characterized by small fault block,small oil area,abundant bottom water energy,higher porosity and higher permeability,looser cementation,and easy sand production.Horizontal well is the main development way.During the process of horizontal well continual production,the water cut went up quickly and the development effects of oil field were seriously affected.In the early stage,the water plugging technology effect of the horizontal wells is poor in oil increment.CO₂ huff and puff technology was put forward to improve productivity and reduce the water cut of horizontal well.The physical model is used to carry out the research on the mutual expansion of CO₂ and crude oil,fluid phase characteristics,compatibility and microscopic flow characteristics.The mechanism of oil increment and water control is determined.According to the mechanism of CO₂ huff and puff techonology in horizontal well,the main control factors and the effect,the well selection method is determined.The horizontal well CO₂ huff and puff design and optimization including the slug length,soak time,fluid producing intensity and other parameters to determine limit cycles and yield changes were researched.When the horizontal well score of heavy oil reservoir is higher than 0.7,and the score of thin oil reservoir horizontal well is higher than 0.6,CO₂ huff and puff technology can be carried out.For horizontal wells of heavy oil reservoir,it is suggested that the volume of gas injection is 1.5×10⁵².5×10⁵sm³ during the first 2 turns.After 2 turns,it is recommended that the periodic gas injection volume is larger.CO₂ is injected at a larger speed,and the soak time is 15³0d.The horizontal well is produced at a smaller liquid production rate.