Offshore Antarctic Peninsula Gas Hydrate Reservoir Characterization by Geophysical Data Analysis

Abstract

A gas hydrate reservoir, identified by the presence of the bottom simulating reflector, is located offshore of the Antarctic Peninsula. The analysis of geophysical dataset acquired during three geophysical cruises allowed us to characterize this reservoir. 2D velocity fields were obtained by using the output of the pre-stack depth migration iteratively. Gas hydrate amount was estimated by seismic velocity, using the modified Biot-Geerstma-Smit theory. The total volume of gas hydrate estimated, in an area of about 600 km 2 , is in a range of 16 × 10 9 -20 × 10 9 m 3 . Assuming that 1 m 3 of gas hydrate corresponds to 140 m 3 of free gas in standard conditions, the reservoir could contain a total volume that ranges from 1.68 to 2.8 × 10 12 m 3 of free gas. The interpretation of the pre-stack depth migrated sections and the high resolution morpho-bathymetry image allowed us to define a structural model of the area. Two main fault systems, characterized by left transtensive and compressive movement, are recognized, which interact with a minor transtensive fault system. The regional geothermal gradient (about 37.5 °C/km), increasing close to a mud volcano likely due to fluid-upwelling, was estimated through the depth of the bottom simulating reflector by seismic data.

Gas hydrate versus geological features: The South Shetland case study

“…Elephant Island; SSI: South Shetland Islands; SFZ: Shackleton Fracture Zone. B) Shaded relief of the high resolution morpho-bathymetry image (modified after Tinivella et al, 2008 andLoreto et al, 2011). Thin black solid lines represent the navigation of the MCS dataset, while the thick black solid lines indicate the part of seismic profiles analyzed in this paper.…”

“…The complex structural setting of the sedimentary prism and the gas hydrate reservoir, highlighted by the presence of a BSR reflector firstly identify by Lodolo et al (1993), were characterised by using the pre-stack depth migrated sections (Loreto et al, 2011). Within the sedimentary prism, three main tectonic elements were interpreted ( Fig.…”

“…We used available velocity models (Loreto et al, 2011) in order to obtain information about porosity variation due to the hydrate presence in an area characterised by a water depth ranging from about 1000 to 2650 m, and a BSR depth ranging from about 500 to 750 m below seafloor. Our main target is to obtain relationship among BSR character, hydrate presence and synclineeanticline structures shaping sediments of the hydrate reservoir.…”

Gas Hydrate and Free Gas Concentrations in Two Sites inside the Chilean Margin (Itata and Valdivia Offshores)

“…The base of the free gas layer reflector, the so called BGR [18], that can be identify below the BSR, was also locally detected. We adopted a procedure that has already tested in several geological contexts in order to determine the gas hydrate and free gas presences and their amount [17,19,23,38,39].…”

An Overview of Mud Volcanoes Associated to Gas Hydrate System

“…This procedure has been applied in the Antarctic Peninsula, where seismic velocities obtained from advanced analysis of multichannel seismic data were analyzed to determine gas hydrate and free-gas distributions and to estimate the methane volumetric fraction trapped in the sediments [170]. The elastic properties of the layers across the BSR were modeled applying the approximation of the Biot equations for seismic frequency in order to quantify the concentrations of gas hydrate and free gas in the pore space [128].…”