Publications

A new method for fractured reservoir characterization has been developed from a wide experience in acoustic logging and the results of theoretical research. The method is based on the use of Shear (S) wave and Stoneley wave attenuation, two parameters obtained from the processing of full waveform acoustic data.The combination of both parameters allows location of individual fractures and fractured zones. The propagation of S-waves and Stoneley waves is based on two different physical mechanisms. Due to this, the combined use of both parameters can help discriminate between individual fractures of large aperture and conductive fractured zones (Stoneley wave attenuation) on the one hand, and individual fractures of lesser aperture or mostly sealed (S-wave attenuation) on the other hand. Since we are able to process EVA data acquired through casing, fracture detection is possible in open and cased hole.The method has been successfully tested on the carbonate reservoirs of the Gaviota gas field offshore Spain as well as on a sandstone reservoir of an oil field in the Gulf of Guinea. Through these 2 examples, in carbonate and sandstone reservoirs, this paper explains how fracture detection was performed with EVA. For the Gaviota wells results were very satisfactory both in open and cased hole and led to significant gas production. For the Gulf of Guinea well, EVA results were checked with the FMS log to demonstrate the validity of the interpretation.