应用恒速压汞技术研究致密油储层微观孔喉特征——以鄂尔多斯盆地上三叠统延长组为例

Application of constant-rate mercury penetration technique to study of pore throat characteristics of tight reservoir:A case study from the Upper Triassic Yanchang Formation in Ordos Basin

针对常规压汞获得的孔喉数值偏低,影响对储层的正确认识及后期开发技术政策的制定等问题,应用消除毛管压力影响的恒速压汞数据对鄂尔多斯盆地延长组致密油储层微观孔喉特征进行了直观、定量的分析。结果表明:致密油储层平均孔隙半径为153μm,与渗透率无相关性;平均喉道半径为0.34μm,是影响渗透率的主要因素,与渗透率具有很强的正相关性;孔喉半径比大,平均为556,与渗透率有较强的负相关性;汞进入阻力较小的大喉道所控制的孔隙时,总毛管压力曲线与孔隙毛管压力曲线几乎重合,喉道的影响不明显,随着进汞量的不断增加,毛管压力逐渐升高,喉道逐渐主导着进汞总量。因此,致密油的规模开发需应用先进的储层改造工艺,充分扩大、增加喉道,降低孔喉半径比,提高储层渗流能力,才能取得更好的开发效果。

The lower pore and throat radius parameters from conventional mercury penetration technique affect the reservoir evaluation and later development technique policy constituting.Based on constant-rate mercury penetration technique,the microcosmic pore throat characteristics of tight reservoir of Yanchang Formation of Ordos Basin were analyzed,and the alterations of pore throat characteristic parameters were also quantitatively and clearly characterized.The average pore radius of tight reservoir is about 153 μm and has no correlation with the permeability.The average throat radius is about 0.34 μm and there is a great positive correlation between the throat radius and permeability.The average ratio of pore and throat radius is 556,and there is a negative correlation between the ratio and permeability.While mercury enters into the bigger pores controlled by wide throats for little resistance,the influence of throats is unclear.With input mercury gradually increasing and capillary pressure rising,throats gradually control whole mercury saturation.Using advanced technique to change reservoir formation to increase or enlarge throat radius and decrease the ratio of pore and throat radius,in order to increase permeability,so the development of tight oil can have a good result.