鄂尔多斯盆地延长组特低渗透砂岩微观孔喉特征的定量评价

QUANTITATIVE EVALUATION OF MICRO-PORE THROAT CHARACTERISTICS IN EXTRA-LOW PERMEABILITY SANDSTONE OF YANCHANG GROUP,ORDOS BASIN

为从微观角度认识特低渗透砂岩的微观孔喉特征,明确制约储层品质和开发效果的关键因素,利用恒速压汞技术对鄂尔多斯盆地延长组的样品进行测试,定量表征孔喉特征参数。结果表明:特低渗透砂岩孔隙之间的差异很小,孔隙半径基本分布于70~225μm范围内,峰值在110μm左右;渗透率小时,喉道分布集中,小喉道含量高,喉道对渗透率的贡献也集中分布,贡献峰值大;喉道半径的分布范围随着渗透率的增大而变宽,大喉道含量及其对渗透率的贡献也随之增大。平均喉道半径与渗透率的相关性较好,渗透率小于1.0×10-3μm2时,平均喉道半径的波动幅度大,特低渗透砂岩敏感的根源在于特殊的喉道特征,物性(尤其是渗透率)差的根本原因在于细小喉道所占比例较大。物性(尤其是渗透率)越好,有效孔隙、喉道越发育。微观孔喉特征的差异主要体现在喉道的大小及其分布上,喉道决定储层品质,影响开发效果。

The samples of Yanchang group in Ordos basin are tested with constant rate mercury penetration technique , pore throat characteristics parameters are characterized quantitatively in order to recognize the micro-pore throat characteristics and to make definite the key factors controlling reservoir quality and development effect. The results show that difference of pore is little,pore radius distributes in 70-225μm,peak value is about 110μm. When the permeability is low,the throat distributes assembly,the content of small throat is high,the contribution of throat to permeability also distributes intensively and contribution of peak value is big. Distribution range of throat radius will become wide,large pore content will increase and its contribution will broaden with the increasing permeability. Average pore radius and permeability present good correlation. Fluctuation amplitude of average pore radius is great when the permeability is less than 1.0×10-3μm2. Sensibility of extra-low permeability sandstone roots in particular throat characteristics. The poor physical properties(especially permeability) lie in the high content of small throat. The well the physical property is,the more the effective pore and throat develop. Difference of micro-pore throat mainly is presented in the pore size and its distribution. The pore controls the reservoir quality and affects development effect.