Seismic attenuation analysis is used to distinguish changes in the spectral and amplitude characteristics of the seismic signal with the purpose of identifying the presence of fluids and fractures within the rock system. The analysis of such changes can be used as a tool for characterizing rock properties and for understanding the behaviour of wave propagation in a complex environment comprised by pores and cracks containing fluids. The study is carried out using high-resolution reflection data obtained from a mature fractured carbonate reservoir near the northeast coast of Mexico. Production from this reservoir is declining considerably. For this reason, a horizontal drilling programme is being considered. The results obtained from in situ measurements indicate that spectral changes and attenuation anomalies are related to the presence of hydrocarbons in the fractured reservoir rocks; however, such anomalies are also related to wave scattering in highly fractured areas. The seismic attenuation patterns associated with the productive zones have helped to identify new potential areas and horizontal drilling targets.