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理论研究和室内实验及生产实际证实 ,在低渗透油气藏中 ,流体在多孔介质中的渗流存在启动压力梯度问题。启动压力梯度的存在 ,导致相同生产压差下 ,产量减少。为了提高低渗油气藏的产能 ,一般必须采取大型酸化或压裂 ,增加近井区渗透率 ,克服近井区启动压力梯度影响问题。经过酸化或压裂这些特殊开采措施后 ,近井区容易形成裂缝。基于这种生产实际问题 ,建立了近井区为双孔介质达西渗流 ,远井区为存在启动压力梯度的低速非达西渗流模型的特殊复合油气藏渗流模型。同时 ,考虑了井筒变井储问题及外边界有界的情况。通过求解模型 ,分析了压力动态特征 ,制作了特殊开采方式下的试井分析样板曲线 ,为特低渗透油气藏的地层参数反求提供了又一新的模型和方法
Theoretical studies and experiments in the lab have proved that there is a problem of starting pressure gradient in seepage of fluid in porous media in low permeability reservoirs. Start pressure gradient exists, resulting in the same production pressure drop, yield reduction. In order to improve the productivity of low-permeability reservoirs, it is generally necessary to adopt large-scale acidification or fracturing to increase the permeability in the near-well region and overcome the influence of the start-up pressure gradient in the near-well region. After the acidification or fracturing of these special mining measures, the formation of cracks near the well. Based on the practical problems of this production, a special composite reservoir seepage model was established, in which the near-well region is Darcy flow of double-porosity medium and the low-velocity non-Darcy flow model of far-well with start-up pressure gradient. At the same time, the wellbore variable well storage problem and the bounded external boundary conditions are considered. By solving the model, the dynamic characteristics of pressure are analyzed, and the curve of well test analysis under special mining mode is made, which provides a new model and method for the reverse formation of ultra-low permeability reservoirs.