Abstract:

At present, the water cut of fault block 14-1 reservoir in Banqiao Oilfield is 98.1 % and the recovery degree is 10.93 %. Conventional water control and oil stabilization technology can not solve the problems of high water cut, low productivity and poor economic benefit. Compared with conventional water control and oil enrichment technology, CO₂ huff and puff cone has the advantages of simple technology, short construction period and high success rate. The mechanism of precipitation and oil increase by CO₂ huff and puff is studied by numerical simulation technology. On this basis, the technological parameters of CO₂ huff and puff are optimized, and the optimal technological scheme of CO₂ huff and puff for horizontal wells in reservoirs is determined. On the basis of scheme optimization, CO₂ huff and puff scheme was implemented on site. The results show that CO₂ huff and puff achieves water control and oil increase in horizontal wells at extra high water cut period by extracting the intermediate components of crude oil through gas drive pressure cone and reducing the viscosity mechanism of crude oil. By comparing the cumulative oil increase and oil exchange rate of single well under different process parameters, the optimal injection rate of CO₂ is 600 t, injection rate is 4.0 t/h, soaking time is 17 d, fluid production is 16 m ³/d, and the number of huff and puff cycles is two. Field pilot test of well 45H shows that the fluid production of well 45H is 12 m ³/d, the water cut is reduced from 98.1 % to 62.5 %, and the oil production is increased from 1.6 m ³/d to 4.73 m ³/d. CO₂ huff and puff can control bottom water coning, reduce water cut and restore productivity effectively. The results show that horizontal well CO₂ huff and puff has good adaptability and application prospect for similar reservoirs in Banqiao Oilfield.

Key words: CO₂ huff and puff, horizontal well, extra high water cut period, Banqiao Oilfield