低渗透油藏中水平井两相渗流分析

Analysis of two-phase percolation of a horizontal well in low-permeability porous media

大量实验表明 ,在低渗透多孔介质中 ,渗流不再符合线性达西定律 ,而具有启动压力梯度 ,本文从 Buckley- Leverret不混溶两相渗流驱替理论出发 ,考虑启动压力梯度的影响 ,对水平井两相渗流进行分析 ,得到了椭球形边水油藏中水平井定产时的压力分布公式和定压生产时的产量公式 ,以及饱和度分布公式。经图示分析得出结论 :启动压力梯度不仅增大油藏的生产压差 ,而且使油藏的无水采收率和水驱采收率减少 ;增大注入量可以降低启动压力梯度对两相渗流的不利影响 ,从而提高水驱采收率 ,因此开发含启动压力梯度油藏 ,应小井距、大流量、大压差进行注水开发 ;

Experiments showed that there is a threshold pressure gradient (TPG) in low-permeability porous media. Based on the Buckley-Leverett fractional flow theory, the linear two-phase flow of a horizontal well were analyzed in low-permeability porous media with the TPG. An elliptic water boundary model was studied. The analysis leads to the following conclusions. For flow in reservoirs with the TPG, oil production in influenced not only by relative permeability, but also by the TPG and production pressure gradient; the existence of the TPG makes the production more difficult, and decreases the no-water recovery efficiency and water-driven recovery efficiency; increasing production pressure gradient can decrease the effects of the TPG and improve the recovery efficiency; the kinds of increasing production pressure gradient include increasing injection rate or decreasing the injection-production distance, so the larger injection rate and smaller injection-production distance should be used in the development of low permeability reservoirs.