低渗透砂岩油藏注水见效时间与井距关系

The relationship between the floodresponse time and the well spacing of the low permeability sandstone reservoirs.

低渗透油藏注水见效时间比较晚，而且反应比较平缓，注水效果与中高渗油藏有明显的不同。在井距２５０～３００ｍ条件下，低渗透油藏油井一般在注水６个月左右开始见效，用常规的压力波影响半径与时间的关系公式不能正确预测。利用稳态逐次替换法，推导出低渗透砂岩油藏压力波的影响半径和时间的关系，并用于预测低渗透砂岩油藏注水见效时间与井距的关系。研究表明，低渗透砂岩油藏注水见效时间为两项之和：第一项反比于导压系数，正比于井距平方，此项为常规的影响半径与时间的关系；第二项反比于注水强度，正比于启动压力梯度和井距立方。实例计算表明第一项远远小于第二项，注水见效时间主要由井距立方项决定，减小注采井距将大大地缩小注水见效时间。实例计算说明该方法是正确实用的。

The water flooding effect shows difference between the low permeability and the middlehigh permeability sandstone reservoirs. The floodresponse time of the low permeability sandstone reservoirs is much longer than that of the middlehigh permeability sandstone reservoirs. For example, the floodresponse time of 250300m well spacing is about 6 months, according to water injection experiments in some low permeability sandstone reservoirs, which can be not correctly predicted by using the conventional correlation between the pressure influence radius and time. The correlation between the pressure influence radius and time of the low permeability sandstone reservoirs is derived by using the steady state replacement method, and applied in the prediction of relationship between the floodresponse time and well spacing of the low permeability sandstone. The theorotical research shows the flood response time is the sum of two parts. The first one is inverse proportional to the pressure transmitting coefficient but direct proportional to the square of well spaceing, this is the conventional relationship between the floodresponse time and the influence radius. The second one is inverse proportional to the intensity of water injection and direct proportional to the starting pressure gradient and the cube of the well spacing. The numerical experiment shows the first one is much smaller than the second one. The application example demonstrates that this methodology is applicable.