An apparatus and method are provided for varying an operating parameter for a nuclear gamma ray tool for evaluating the integrity of gravel packing. The gamma ray outpat intensity and area of investigation are altered by changing a source housing geometry and the material from which the source housing is made. An actuator is provided to slide a variable electron density sleeve over the source and to vary the area of investigation by changing the distance between the source and a detector.
Ralph Tutor, Louise Prince, Larry King, Alfred Gardner, Jerry Hamilton, Anita Penny, Ruth Arnold, Anne Arnold, Barbara Matthews, Linda Ball, Brenda Tutor, Barbara Gardner