特低渗透多层油藏水驱前缘研究

特低渗透多层油藏在注水开发时由于各储层物性和流体特征存在差异,会引起各储层注水推进速度不同.利用特低渗透油藏渗流理论建立理论模型,推导了多层油藏考虑油相和水相启动压力梯度的水驱前缘计算公式,分析了渗透率级差、注采压差、注采井距、地层原油粘度对注水推进速度的影响.并针对注采井距的影响,首次提出了无因次水驱前缘的概念.研究结果表明,渗透率级差越大,渗透率相对较小储层的水驱前缘推进越慢；随着注采压差的增大,渗透率相对较小储层的水驱前缘推进速度逐渐增大,但增幅逐渐变缓；随着注采井距的增大,渗透率相对较小储层的水驱前缘推进速度逐渐变快,但无因次水驱前缘却逐渐变小；随着地层原油粘度的降低,渗透率相对较小储层的水驱前缘推进速度逐渐变快,且增幅逐渐变大.

Study on water-oil frontal edge for ultra-low permeability multilayer reservoir

Difference of physical property of each stratum can cause different advancing velocity of water-oil frontal edge during the waterflooding stage in ultra-low permeability multilayer reservoir. Using seepage theory of ultra-low permeability multilayer reservoir,considering threshold pressure gradient for oil and water, a theoretical model is established and the formula of water-oil frontal edge is deduced. In addition, the influence of permeability differential, injection-production differential pressure, injection-production well spacing and oil viscosity on the water-oil frontal edge is also analyzed. Considering the influence of injection-production well spacing,the dimensionless water-oil frontal edge is first proposed. The result shows that: The greater the permeability differential, the slower the advancing velocity of water-oil frontal edge for the lower stratum; with the increase of the injection-production differential pressure, the advancing velocity of water-oil frontal edge for the lower stratum is becoming faster, but the amplitude increment is becoming smaller; with the increase of the injection-production well spacing, the distance of water-oil frontal edge for the lower stratum is becoming longer, but the dimensionless water-oil frontal edge is becoming smaller; with the decrease of oil viscosity, the advancing velocity of water-oil frontal edge for the lower stratum is becoming faster, and the amplitude increment is becoming larger.