Determination of production of hydro-carbons has long been an important use of borehole geophysical logging.  Century’s Express Stack tools combine these most important logging tools in a single run of the well, with gamma ray, caliper, density – neutron porosity, spontaneous potential, shallow-medium and deep induction resistivity.  Other logs can be combined to include borehole deviation, sonic velocity, and micro-resistivity measurements.  The tools with a smaller 2.5 inch diameter than most of the major suppliers, allow access to smaller diameter exploration holes.  The complete triple combo stack is 45 feet in length and weighs 250 pounds.