低孔隙度低渗透率天然气储层声波岩石物理研究

Acoustic Rock Physics Property Research on Gas Bearing Reservoir with Low Porosity and Low Permeability

为了研究声波在低孔隙度低渗透率含气储层中的传播规律,采用改进的White气包模型,模拟低孔隙度低渗透率储层中不同频率纵横波性质随不同含水饱和度的变化,并与常规及高孔隙度高渗透率储层结果进行对比,得出低孔隙度低渗透率储层与常规和高孔隙度高渗透率储层声波随不同含气饱和度变化规律的区别,以及气包半径的选取对声波传播规律的影响,且结合实验室测量结果进一步验证分析的正确性。频率一定,低孔隙度低渗透率储层与常规储层及高孔隙度高渗透率储层规律相似,声波速度和衰减对储层含气也有一定的灵敏度,但随含水饱和度迅速增大的起跳点对应含水饱和度值变小。

In order to know the propagation law in reservoir with low porosity and low permeabil- ity and provide theoretical base, a modified White model is used to simulate different water satu- ration variations of compressional wave and shear wave properties with different frequencies in reservoir with low porosity and low permeability, the result of which is compared with that of conventional reservoir and high porosity and high permeability reservoir, and the differences of the acoustic propagation property between low porosity and low permeability reservoir and other reservoirs are summarized. Further more, the effect of gas pockets on acoustic property is ana- lyzed. On the basis of theoretical simulation and the lab data, the differences of the acoustic prop- erty in the reservoir with low porosity and low permeability and other reservoirs are analyzed, and how to select gas pocket radius is also given. The results show that when the frequence is un- changeable, the propagation law in reservoir with low porosity and low permeability is similar to that in conventional reservoir and high porosity and high permeability reservoir. The acoustic ve- locity and attenuation all change significantly when the reservior contains gas, only with a smaller gas saturation take-off point.