Heather Callaghan's job has her providing some pretty vital information to oil companies. "I'm their eyes and ears," says the Petroleum Technologist/Well Site Geologist, who works for one of the largest geological consulting firms in the world. The firm assigns her to oil rigs, where she analyzes the rock being drilled and assesses the zone's potential for oil and gas production.		Heather looks at samples that have been collected from the drilling mud. What looks just like muck to the naked eye can, with a microscope and a fluorescent light, tell her the properties of the rock below and the type of fluid it contains. Studying a core - a cylinder about twice the length of a flag pole - can give her more clues, such as how much oil can be found. The pores and cracks in its rock, which make good reservoirs for oil, are the litmus test for a well-site's production potential. The speed of the drill will also shed clues about the volume of oil. The faster the speed, the more porous the rocks.