Natural Gas emanations at the Campeche Sound in the Gulf of Mexico have caused in some cases the failure of soils under existent platforms. The gas pockets that were detected in shallow geophysical surveys prior to the platform installations have migrated invading the area of some platforms. The presence of these shallow gas pockets and sudden gas emanations (blow out) is a cause of concern regarding the safety of the existent and planned platforms. An investigation was carried out in order to assess the effect of the gas emanations and the presence of the shallow gas on the safety of the platforms. The investigation included a desk study with the purpose of integrating all relevant information from the reservoir and up to the sea bed with the participation of all the disciplines involved. On these bases, a field investigation was planned, to confirm the results of the desk study. This investigation included the application of several new techniques in the exploration field. The field investigation included geophysical, geotechnical and geochemical exploration, as well as the installation of a monitoring system to better understand the complex gas effects on the structures foundation. A 3D high resolution seismic survey was used to investigate the origin and dimensions of the shallow gas pockets. Te evaluation of the effects of shallow gas and hydrocarbon deposits on the existing and proposed structures in the Cantarell field was achieved through an integrated analysis of the geophysical data, in situ measurement of pore pressure, in situ and laboratory geotechnical analysis of gas in soil boring profiles, special static and cyclic laboratory testing on hydrocarbon saturated soils, and special cyclic testing on gas-saturated granular soils. The study shows that the current levels of pressure in the hydrocarbon pockets are not expected to affect the existent structures safety; however, as it has happened in the past, it is possible that pressure could build up and cause a sudden gas expulsion affecting existing platforms. Taking this in consideration a monitoring system was installed in order to measure the pressurization of the foundation zone strata that could result in weakening of the soil response affecting the structure stability.
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