鄂尔多斯盆地超低渗透油层开发特征

鄂尔多斯盆地长8、长6超低渗储层石油资源潜力巨大,开发难度大.该类储层物性差,非均质性强.通过室内实验与现场试验研究,探讨了超低渗开发面临的主要问题:孔喉细小、孔隙结构复杂,排驱压力大;可动流体饱和度低;启动压力梯度大;应力敏感性强;非达西渗流特征明显;注水启动压力高,视吸水指数低,地层压力保持水平低,难以建立有效压力系统.由于传导能力差,注入水主要集中在井眼附近,使得地层压力增大,渗透率升高.生产特征是产量递减快、压力下降快,压力下降导致储层骨架发生塑性变形而造成孔隙减小、渗透率降低.

Development characteristics of super-low permeability oil layers in Ordos Basin, China

Chang-8 and Chang-6(Member 8 and 6 of Upper Triassic Yanchang Formation) super-low permeability reservoir in Ordos Basin have large oil resources.But they have strong heterogeneity and poor physical properties,and are hard to develop.This paper discusses the main difficulties,such as the micro pore throat,complex pore structure,high driving pressure,low saturation of moveable fluids,high threshold gradient pressure(TGP),strong stress sensitivity and evident Non-Darcy seepage characteristic.The water flooding feature is the high injection TPG,low injectivity index,hard to maintain low formation pressure and unable to set up the efficient pressure system.However,because of the low transmissibility,the injected water concentrates around holes to result in increasing the pressure and permeability.But as for the production feature,the pressure decreases fast with the fast decline of production,and the plastic deformation of the rock framework which results from the decrease of the reservoir pressure leads to the drop of porosity and permeability.