WELL LOGGING

Well logging is an important contributor to formation evaluation. The objectives of formation evaluation include assessing resource size, supporting the placement of wells, and interpreting reservoir performance during development. Logging tools can be designed to measure such physical quantities as electromagnetic and sonic wave signals that pass through a section of the formation and detect elementary particles emitted by formation rock. This chapter introduces the well logging environment, describes different types of logs, explains why combinations of logs are used, and discusses techniques and limitations of well log interpretation. The environment includes such factors as rock type and structure, fluids in the well and adjacent formation, temperature and pressure. The chapter considers three types of lithology logs in this section: the gamma-ray log, the spontaneous potential (SP) log, and the photoelectric effect (PE) log. Porosity logs include density logs, acoustic logs, and neutron logs.