The Upper Jurassic (Tithonian) Edzna Formation is considered to be the most important source rock in the southeastern Mexico Campeche shelf, Gulf of Mexico. The formation is penetrated by a number of wells, in which cumulative and test production show that the Edzna Formation also is an important hydrocarbon reservoir. The formation is composed of a condensed section of mudstone and bentonitic shale. Thicknesses vary between 62 m and 120 m in the northeastern area, thickening to 393 m in the central marine area. The structural top commonly reaches depths of 6100 m in the southwestern and western areas, with a minimum depth of 1600 m in the northeast. There is a distance of approximately 120 km between deepest and shallowest burial areas. There are three important structures in the Campeche shelf: the Ceeh-Cantarell anticlinorium in the northeast, the Sinan-Mison syncline in the central area, and the May-Oktan anticlinorium in the southern area of the marine region. The northeast-southwest-trending Edzna Formation reservoir is about 150 km long by 50 km wide. To date, cumulative oil production is about 45 million barrels.