Abstract

Aimed at ultra-low permeability reservoirs, the recovery effect of inverted nine-spot equilateral well pattern is studied through large-scale natural sandstone flat model experiments. Two adjustment schemes were proposed based on the original well pattern. This essay has put forward the concept of pressure sweep efficiency for evaluating the driving efficiency. Pressure gradient fields under different drawdown pressure were measured. Seepage area of the model was divided into immobilized area, nonlinear seepage area and quasi-linear seepage area combining with the nonlinear seepage experiment of the small twin core. The results showed that the ultra-low permeability sandstone flat model was characterized as nonlinear seepage law and threshold pressure gradient obviously. For one quarter of the inverted nine-spot equilateral well pattern, the middle region is difficult to develop. The recovery effect can be improved by adjusting production wells or adding injection wells. And the best solution is transforming the corner production well into injection well.

Keywords:

Low permeability reservoirs, large-scale sandstone outcrops model, pressure sweep efficiency, threshold pressure gradient, well pattern adjusting,

References

Competing interests

The authors have no competing interests.

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The authors have no competing interests.