Experimental study on adaptability of well pattern using sandstone plate model with ultra-low permeability
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Abstract:
Because the porous flow state is difficult to be simulated by one-dimensional cores and two-dimensional sand filled models，this paper proposes a method of making large-scale natural outcrop flat model and defines two parameters to evaluate adaptability of different well pattern on the ultra-low permeability sandstone flat model. With natural sandstone plate model，production of different well patterns in homogeneous oil reservoirs is simulated. A concept of pressure sweep efficiency and deliverability index for researches on adaptability of well patterns are put forward. Through experiments，plane pressure gradient field of different well patterns under different drawdown pressures are measured，and then seepage areas of the models are divided into immobilized seepage area，nonlinear seepage area，and quasi-linear seepage area，with the help of small core nonlinear seepage curve. Experiments show that adaptability of inverted nine-spot equilateral well pattern is better than those of inverted nine-spot rhombus well pattern and rectangular well pattern. With the increase of drawdown pressure，deliverability index of all well patterns increases，immobilized seepage area reduces，and quasi-linear seepage area expands. At the same time，nonlinear seepage area of inverted nine-spot equilateral well pattern reduces，while those of inverted nine-spot rhombus well pattern and rectangular well pattern fluctuate as expanding first and then reducing.
