The Electromagnetic Propagation Tool (EPT*) is a downhole microwave instrumentation devicewhich channels 1.1 GHz energy into the formation and measures the tra1!el time and attenuation of the miCrOW41!e signal as it propagates through the invaded zone. The rele~'ant electromagnetic field theory, the basic measurement technique, and the tool block diagram are reviewed. The present interpretation techniques are then discussed, followed b" several log examples which show the utility of the EPT. Specifically, the EPT-derived porosity, when compared with neutron/density porosit)'. allows one to distitlgutsh hetween h)ldrocarbonbearing and water-bearing zones in formations ha1'ing var.1,ing lithologies and water salinities. 2 SPE 9267

The basic theory upon which the microwave Electromagnetic Propagation Tool (EPT) has been founded is reviewed, and the measurement technique is discussed in terms of a functional block diagram. Two methods of interpreting the propagating wave's measured phase and attenuation are reviewed. Specific log examples which distinguish between hydrocarbon and water-bearing zones in several lithologies are presented..

Reservoirs with thin laminations can be more accurately evaluated by using logging tools with inherently better vertical resolution, by employing enhanced vertical resolution input processing methods, and by incorporating interpretation models that properly handle log inputs with different vertical resolutions and reconstruct all outputs with high vertical resolution. The paper discusses a specific high-resolution interpretation model and provides comparative analyses of how model outputs are affected by the vertical resolution of its input logs and by the reservoir type. Three field examples are provided. Increases in predicted hydrocarbons were noted in two of these examples when the input log resolution was increased. In these two examples, the observed increases were confined to a number of isolated thin beds. In the third field example, significant decreases in predicted hydrocarbons were observed when high-resolution input data were used; the reservoir in this case appears to illustrate thin sand-shale laminae extended over a 27 metre interval.