A DLIS file is a log file created by sensors that monitor petroleum wells, which are holes drilled in the ground for the purpose of exchanging petroleum between a subsurface reservoir and the surface. It contains a database of well measurements such as resistivity, porosity, sonic, and magnetic resonance measurements. DLIS files are saved in the Digital Log Interchange Standard used for interchanging well log data.

Sensors are placed in petroleum wells to monitor their activity. These sensors create log data files with the main purpose of determining if a formation contains commercial quantities of hydrocarbons. One of the formats that well log data files are saved in is the DLIS format. This format was introduced in 1991 and is still used today for the interchange of well log data. The DLIS format separates data into layers, which consist of media, format, model, schema (descriptions of objects), and dictionary. The DLIS file can be viewed by the PPDM data model. PPDM stands for Professional Petroleum Data Management, which is an association that creates baseline definitions and practices around Exploration & Production (E&P) data management. You can also use DlisBrowser to view the full structure of DLIS files. DLIS files may be converted to the ASCII and LIS formats using Oilware EzTools.