Research and practice on development mode of Caofeidian bottom-water heavy oilfield with low structural amplitude in Bohai Sea during ultra-high water cut period
Caofeidian oilfield group is the largest bottom-water heavy oilfield in the Bohai Sea,with low structural amplitude,low oil column height,and high formation oil viscosity.After more than ten years of development,Caofeidian oilfield group has entered the ultra-high water cut period.However,the current oil production rate and the water drive recovery rate are low,which requires comprehensive adjustment.Through laboratory experiments and water drive model deduction,the characteristics of water ridge in horizontal wells and the variation law of water drive sweep efficiency in bottom-water heavy oil reservoirs were studied.The results show that the ridge progression in a single zone is serious during drilling,and the displacement along the horizontal well is unbalanced.The water drive sweep efficiency of the horizontal well rises slowly in the early stage and increases continuously in the late stage,indicating that increasing oil production volume can improve water drive sweep efficiency.On this basis,key technologies are proposed,such as horizontal well network infill adjustment technology based on water ridge evolution law,precise horizontal well deployment technology based on integrated structures and reservoir descriptions,and large-displacement oil extraction technology based on the effective utilization of pores.Then,the overall horizontal well infill adjustment model is established,featuring combined mature areas during the ultra-high water cut period and new areas,intersected mature wells and new wells,and longitudinally zoned and horizontally sectioned patterns.After the adjustment,the degree of reserve utilization of the oilfield is increased by 21.3 percentage points,and the oil recovery rate is increased by 1.3 times.The water drive recovery rate is increased by 10.9 percentage points,realizing rapid production and continuously stable production during the ultra-high water cut period and providing a reference for the long-term continuously stable production and efficient development of offshore oilfields.
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