Abstract: Reservoir information for determining residual oil saturation is obtained by injection of a partitioning tracer and a non-partitioning material through an injection well and periodically logging a second well spaced from the injection well to determine time of passage and amount of said injected materials. A preferred partitioning tracer is iodoethanol containing iodine 131, and the second material may be a radioactive tracer having a gamma ray emission spectrum different from the partitioning tracer or it may be a brine having a salinity different from that of formation water in the reservoir.

Abstract: A partitioning radioactive tracer material is prepared by reacting an alkali-metal salt of radioactive iodine with chloroethanol in the presence of activated carbon.

Abstract: An improvement in the method of determining oil saturation in a subterranean formation, penetrated by a well-bore, is disclosed. In the method of determining oil concentration by measuring thermal neutron decay with a low salinity aqueous liquid in said well-bore and said formation, and measuring thermal neutron decay with a high salinity aqueous liquid in said well-bore and said formation, the improvement comprises adding to said low salinity liquid in the well-bore, only, a material which adjusts the thermal neutron capture cross section of the well-bore so that it is approximately the same as the thermal neutron capture cross section of the well-bore when it contains the high salinity liquid.

Abstract: A method is provided for determining the shale content of mined coal by monitoring the thorium content of the coal. Thorium content and ash content are shown to be related whereby a direct reading of the thorium will be indicative of the shale content of the coal and the ash content of the coal. The method utilizes the natural radiation of thorium to provide the continuous or selective control of mined coals.

Abstract: A method for determining the distance from a given point in a coal seam to shale by sensing the thorium radiation from shale layers positioned about the coal seam. The invention is useful for maintaining a drill in a desired position in a coal seam and guiding the drill in response to the sensed radiation.