Disclosed is a method of determining the extent of recovery of materials injected into oil wells or subsurface formations. The method includes injection of one or more tracers into an oil well or into a formation. Included in the method are the steps of introducing a material of interest into the oil well or into the subsurface formation associated with the bore of the oil well; introducing a tracer into the oil well or into the subsurface formation associated with the bore of the oil well; recovering from the oil well a production fluid, analyzing the production fluid for a concentration of the chemical tracer present in the production fluid; and calculating the amount of material of interest recovered from the oil well using the concentration of the chemical tracer present in the production fluid as a basis for the calculation.