Abstract: The thin interbedded reservoir with low permeability in Bohai Oilfield is characteristic of long span, developed bottom water and highly interbedded sand-mud layer. Large displacement cross-layer fracturing is an important means to develop long-span thin interbeds, but there is no related offshore practice and research. For Shahejie reservoir with low permeability and thin interbeded sandstone in Bohai Oilfield, the effect of perforation location and stage limit on fracture propagation at 5~12 m$^3$/min fracturing displacement rate is studied and unperforated height of thin bottom-water interbeded reservoir is determined by establishing a thin interbeded fracture propagation model. The results show that there is an optimal value of perforation cluster number for different displacement rates. When the perforation cluster number is less than this value, the fracture can penetrate the layer longitudinally, but the layer number of perforation transformation is limited. When the perforation cluster number is more than this value, the fracture is difficult to penetrate the layer and is restricted within the perforation layer. The 12 m$^3$/min single-stage fracturing pump rate combined with multi-cluster perforation can be used to fully stimulate the 50 m thin interbedded reservoir. For the long-span thin interbedded reservoir of more than 50 m, the multi-stage fracturing combined with large displacement rate is an effective means to fully stimulate the thin interbedded reservoir. With the increase of displacement rate, the unperforated height in the bottom water reservoir should increase. Under the fracturing displacement rate of 12 m$^3$/min, the unperforated height of the bottom water reservoir in Shahejie should exceed 9.5 m. The research results can provide a theoretical basis for the large displacement fracturing construction design of large-span thin bottom water interbeded reservoir in the Bohai Oilfield.

Key words: Bohai Oilfield, low permeability thin interbed reservoir, high pump rate fracturing, perforation, staged fracturing