Gas hydrate identification and distribution in the Mexican Ridges, Mexico

Abstract

We mapped gas hydrates, free gas and Bottom Simulating Reflector (BSR) distributions in an area of Mexican Ridges, central Gulf of Mexico, Mexico, revealing the relationship between these three elements and the tectono-stratigraphy. The three elements are more visible when the host rock is a high porosity sandstone because there is a large seismic impedance contrast between solid gas hydrates above and free gas below, which manifests itself on the seismic as a BSR. Gas hydrates are identified in the well as higher resistivity sandstone layers with a strong positive amplitude. When the host rock is has a higher shale content with lower porosity, the impedance contrast is lower and the BSR is weak or not visible. On the other hand, Mexican Ridges are a series of anticlines where gas hydrates and free gas are trapped on the crest after migrates through the dipping layers and faults from synclines where are generated in calcareous shale. The main seal is MTC deposits from Pliocene, when they are not deposited at the crest of anticline there is gas escape o seafloor in form of gas chimney. On this way, we established a complete petroleum system for gas hydrates and free gas on Mexican Ridges.