Automated Karstic Reservoir Analysis Utilizing Attributes

The aquifer studied, 20 to 130 m in depth, consists of tight karstic carbonates. In 2004, 3D seismic data were recorded. The resulting high resolution 3D seismic block revealed three high-porosity, presumably-water-productive, layers. In 2014, full waveform acoustic data have recorded in 11 wells in order to evaluate the potential of the acoustic method to detect karstic bodies and flows, the results being compared with seismic data, BHTV logs and flow measurements.

The paper describes the methodology developed to process acoustic data when they are corrupted by noise. The automated procedure is based on Singular Value Decomposition processing which is used to estimate simultaneously the velocity of the formation, the amplitude of the acoustic signal and the level of noise. An attribute, named Noise/Signal detector, has been calculated to detect karstic levels. The results obtained on 11 wells are confirmed by BHTV logging data and at a large scale by seismic data (VSP and 3D seismic). The acoustic data have also been compared with PLT data. An attempt to obtain an acoustic flow detector has been done. The conclusions of the study show that acoustic logging can be fruitfully used to detect productive levels but cannot guarantee flow circulation.