砂岩储层地震属性参数对孔隙流体的敏感性评价

对于不同特性的砂岩储层,从地震数据所提取的多种属性参数对孔隙流体变化的响应是有一定差异的。利用统计学原理给出了流体指示因子的计算方法,用于定量评价地震属性参数对孔隙流体变化的响应差异。利用胜利油田沙河街组三段砂岩储层在模拟储层条件下的实验结果,采用属性交会图技术验证了流体指示因子的正确性。对于疏松砂岩及中-高孔隙度固结砂岩,利用纵、横波阻抗差等常规地震属性可较好地判别孔隙含气及饱和水、饱和油状态;而对于致密含气砂岩,纵、横波速度比及泊松比对流体变化相对较为敏感。对于疏松砂岩,由双敏感属性参数所构成的交会图可区分饱和油与饱和水状态,但利用常规属性交会图难以区分固结砂岩孔隙饱和水与饱和油。在准确给出干燥岩石纵、横波速度比的基础上,组合属性参数I_p²-c.I_s²相对于常规属性对孔隙流体变化更为敏感,构成的属性交会图对饱和水与饱和油砂岩样品的实验结果具有明显的区分能力。

Sensitivity evaluation of seismic attribute parameters for sandstone reservoir to pore fluid

The response of seismic attribute parameters to variation of pore fluid is different for various sandstone reservoirs.A calculation method for fluid indicator is given by the statistical method and used to reflect the response difference of seismic attribute parameters to fluid variation.Experimental results of sandstone reservoir in the third member of Shahejie Formation in Shengli Oil Field proved the applicability of this approach using seismic attributes crossplot technique.According to the calculation results of fluid indicator,the conventional attributes,such as response difference of P wave and S wave,are sufficient for discrimination of gas state in middle-high porosity unconsolidated sandstones and cemented sandstones sample saturated with water and oil.For the tight sandstone containing gas,only velocity ratio of P wave to S wave and Poisson ratio are sensitive to fluid variation.For the unconsolidated sandstones,the crossplot can be used to distinguish saturated oil from saturated water by selecting two sensitive attribute parameters according to their relative values of fluid indicator.For the cemented sandstone,this approach is not applicable.On the basis of exact velocity ratio of P wave to S wave in dry rock,a combined attribute parameter is more sensitive to pore fluid variation than the conventional attributes.The crossplot generated from the combined attribute parameter has an excellent discriminatory capacity for the experimental results of sandstone samples saturated with water and oil.