低渗储层有效喉道半径下限研究:以苏北盆地高邮凹陷沙埝南地区为例

Cutoff Value of Effective Throat Radius in Low Permeability Reservoir:An Example of South Shanian Area in Gaoyou Depression,Subei Basin

针对前人研究较少的储层有效喉道半径下限的影响因素,以苏北盆地高邮凹陷沙埝南地区阜三段储层为研究对象,利用常规压汞和恒速压汞方法对其进行研究,并对其在低渗储层中的特殊性进行了探讨。研究发现,有效喉道半径下限并非一个定值,而是随渗透率增大而提高;在孔喉特征参数中,其随喉道半径增大、分选变差(分选系数、变异系数增大)而提高;其与平均喉道半径的相关性(R2=0.9659)好于与最大连通喉道半径的相关性(R2=0.8796);当有效喉道半径下限<1.5μm时,其值随均质系数增大而减小,当有效喉道半径下限>1.5μm时,其与均质系数无明显关系。对于低渗储层而言,随着储层岩石中粗大喉道数量增多、半径增大,喉道间的非均质性变强,有效喉道半径下限也随之提高。

The influential factors and genesis of low limit of effective throat r adius are analysed by using data of mercury-injection capillary pressure curve a nd rate-controlled mercury injection.The specific characteristics in low permea bility reservoir are also discussed.The results indicate that cutoff value of e ffective throat radius rises with the increase of permeability.In the character istic parameters of pore structure,it rises with the increase of throat radius and worsening of sorting（coefficient of sorting and coefficient of variation be ing higher）.The relationship with the average throat radius is better than that of the largest throat radius,with their coefficient correlation selectively be ing 0.965 9 and 0.879 6.When cutoff value of effective throat radius is smaller than 1.5 μm,it decreases with coefficient of the increase of uniformity.When cutoff value of effective throat radius is greater than 1.5 μm,their relation ship is not obvious.In the low permeability reservoir,with the increase of thi ck throat′s radius and its quantity,anisotropy of throats is increasing,and c utoff value of effective throat radius becomes higher.