Field and laboratory data indicate anomalously high reflectivity from fluid-saturated reservoirs at the low-frequency seismic range. It also has been observed that the reflected signal is frequency-dependent and is strongly related to the reservoir flow properties. We have obtained an asymptotic representation of the seismic reflection from a fluid-saturated porous medium in the low-frequency domain. The frequency-dependent component of the reflection coefficient is proportional to the square root of the product of frequency of the signal and the mobility of the fluid in the reservoir. This provides an opportunity for locating the most productive zones of the field before drilling. In the presented example we quantify low-frequency imaging amplitude attribute in terms of reservoir fluid mobility and reservoir production rate.