Electromagnetic Propagation ... A New Dimension In Logging

Abstract

Abstract One of the primary requirements of well logging is the ability to distinguish between oil and water. Resistivity/Conductivity and pulsed-neutron tools can do it if the water is fairly saline, and if its salinity is known. However, a method has long been needed that is less dependent upon knowledge of water salinity. Schlumberger's new Electromagnetic Propagation Tool measures the phase shift and attenuation of microwave-frequency energy propagated through the formation near the borehole. From these measurements, it is possible to derive values of porosity and water saturation that are practically porosity and water saturation that are practically independent of water salinity, except in ranges close to saturation. Notable is the fact that the new tool is most accurate in fresh waters, an area that has been troublesome. An experimental tool has been in the field for many months, running logs in eight states and a Canadian province. Field test results have exceeded expectations, and equipment is being built for commercial service. This paper gives the operating principles of the tool, describes the interpretation method that has been developed, and presents several field examples to illustrate the importance of this new logging measurement.