基于连续变地层胶结指数m值的含水饱和度计算方法——以渤海油田复杂砂岩储层为例

Water saturation calculation method based on continuous variable cementation exponent m:a case study of complex sandstone reservoir in Bohai oilfield

近年来,在渤海油田发现了许多复杂砂岩储层,岩石类型多样化和分选性差,导致孔喉结构多变、物性差异大、地层非均质性强和岩电参数不确定性大,难以准确计算地层饱和度。提出了适合本区的基于连续变m值的饱和度计算方法,即在高分辨率能谱测井计算出地层岩石密度骨架值的前提下,先利用地层声波时差与密度交会的方法反推地层岩石声波骨架值,然后根据J.P.Martin等提出的声波地层因素公式计算出反映地层孔喉结构几何特征的声波迂曲度系数,并建立岩心分析得到的地层胶结指数m与声波迂曲度系数之间的关系,最后将得到的连续变m值代入阿尔奇公式计算出地层饱和度。实例分析表明,本文方法可以较准确地计算出地层原始含水饱和度,从而实现了对复杂砂岩储层饱和度的定量解释,可以为今后其它复杂砂岩油气田的定量解释提供思路。

In recent years, many complex sandstone reservoirs have been discovered in Bohai oilfield with wide various rock types and poor sorting which cause complicated pore throat structure, large difference on physical properties, strong heterogeneity, rock-electro parameters uncertainty and low accuracy of water saturation calculation. A saturation calculation with continuous variable m is presented for the study area. Firstly, formation matrix acoustic value is inversed with acoustic-density intersection based on the matrix density value calculated with Litho Scanner. Then, the acoustic tortuosity coefficient reflecting the formation pore throat structure is calculated according to the acoustic formation factor formula published by J. P. Martin, and the relationship between cementation index and the acoustic tortuosity coefficient with core analysis is established. Finally, the continuous variable cementation exponent m is substituted into Archie equation to calculate formation water saturation. The practical analysis shows that the method can calculate original formation water saturation accurately and provide a way for quantitative interpretation in complex sandstone reservoir.