Abstract:

CO₂ huff and puff in horizontal wells, especially in small fault block reservoirs with imperfect well pattern and thin inter bed oil reservoirs, is an effective technical supplement for CO₂ flooding. For high water-cut horizontal wells, as there are three limitations of the ″elliptical cylinder model method″—a fast calculation method for the design of CO₂ injection volume in horizontal wells, a new CO₂ injection volume calculation formula based on the improved cylinder model is proposed. Compared with the optimized results of numerical simulation method, the calculated error rate of the new formula is less than 10 % so as to meet the needs of industrial design. Besides, compared with the old model, the calculation accuracy is enhanced considerably. The new formula is used to design the CO₂ huff and puff scheme of remaining oil development of well S49P1, a typical high water-cut horizontal well in J oilfield. And a good incremental oil effect and economic benefit was achieved, which verifies the adaptability and reliability of the improved model. The establishment of the new model can provide a more accurate engineering calculation tool of CO₂ injection volume for CO₂ huff and puff in other horizontal wells with high water-cut.

Key words: high water-cut horizontal well, CO₂ huff and puff, injection volume, improved elliptical cylinder model, dispersion radius