Abstract: Imitation horizontal wells can significantly enlarge single well drainage area and increase controlled reserves,thus effectively develop low-abundance and ultra-low permeability reservoirs.In order to accurately and rapidly predict steady-state productivity of various imitation horizontal well patterns,deliverability prediction models with start-up pressure being taken into consideration were established for different imitation horizontal well patterns by using stream tube flow line integral method based on seepage flow characteristics of imitation horizontal wells.Comparison of the modeling results with actual production shows that the models are accurate in productivity prediction with an error less than 8.04% only.The models also show that staggered well pattern is better than cross well pattern in terms of steady-state productivity and sweep area when the lengths of the imitation horizontal well are the same.The latter is also more sensitive to well length than the former.The study may help theoretically guiding the application of imitation horizontal wells in ultra-low permeability reservoirs.

Key words: productivity, penetration ratio, imitation horizontal well, injector-producer pattern, low-permeability oil reservoir