孔隙结构对低孔低渗储集层电性及测井解释评价的影响

Influence of pore structures on electric properties and well logging evaluation in low porosity and permeability reservoirs

近年的研究发现,在低孔低渗储集层中,孔隙结构直接影响储集层产能评价和油、气、水层测井评价的准确性。分析了研究地区低孔低渗储集层的孔隙结构特征及其对储集层产能和电性的影响,发现对于纯水层而言,在地层水电阻率及其他因素相同的情况下,孔隙喉道连通性越好电阻率则越低,相反,孔隙结构越差(孔隙喉道连通性不好)电阻率则越高,有些孔隙结构差的水层电阻率甚至会超过油层的电阻率,因而地层电阻率对油、水层分辨能力降低,测井解释难度增加。研究表明,根据不同孔隙结构改变岩电参数m值,可较好地解决孔隙结构影响低孔低渗油、气、水层测井解释准确性的问题。研究区块的应用表明,采用可变的m值计算储集层的含油饱和度来评价油水层,可取得较好的效果,使得低孔低渗储集层测井解释符合率由原来的64%提高到85%以上。

Recent investigation indicates that the accuracy of reservoir productivity evaluation and well logging identification of oil, gas and water zones in low porosity and permeability reservoirs are affected by their pore structures. This paper analyzed the characteristics of pore structures in low porosity and permeability reservoirs and their influence on productivity and electric properties. It was found that for net water layers, the better the reservoir pore-throat conductivity was, the lower the formation resistivity, if the other affecting factors were the same; the worse the pore-throat conductivity, the higher the formation resistivity. The resistivity of some water-bearing layers with poor pore structure was even higher than that of oil-bearing layers, resulting in decrease of the identification capacity of formation resistivity method and increase of difficulty in well logging interpretation. Good results can be obtained in evaluating oil and water zones by calculating their oil saturations with the changeable m value, which can raise the consistency of well logging interpretation of the reservoirs from 64 % to 85%.