Sediment damage caused by gas exsolution: a key mechanism for mud volcano formation

Type Article
Date 2019-12
Language English
Author(s) Blouin Arthur1, 2, 3, Sultan NabilORCID1, Callot Jean-Paul3, Imbert Patrice2
Affiliation(s) 1 : Ifremer, LAD, géosciences marines, REM, Centre de Bretagne, 29280, Plouzané, France
2 : R&D/EP Total S.A., Avenue Larribau, 64000, Pau, France
3 : CNRS /TOTAL/UNIV PAU & PAYS ADOUR/ E2S UPPA, Laboratoire des Fluides Complexes et leurs Réservoirs‐IPRA, UMR5150, 64000, PAU, France
Source Engineering Geology (0013-7952) (Elsevier BV), 2019-12 , Vol. 263 , P. 105313 (18p.)
DOI 10.1016/j.enggeo.2019.105313
WOS© Times Cited 3
Keyword(s) Consolidation testing, Gas exsolution, Gassy sediments, Sediment damage, Mud volcano
Abstract

Gassy sediments are common in marine environments and are characterized by a specific mechanical behavior significantly different from that of water-saturated sediments. It is shown that gas causes damage and initiates fractures in sediments. To define the controlling parameters dominating the damage process during gas exsolution and its consequences in terms of hydro-mechanical behavior, we developed a specific consolidation apparatus to test sediments collected from the active Absheron Mud Volcano. Indeed, mud volcano formation is initiated by gas exsolution and subsequent mud generation at depth from stratified sediments.

Gas was generated in the samples by circulating carbonated water through the fine-grained sediments, then decreasing the total pressure. Particular attention was given to the impact of gas saturation and associated damage and fractures on P-wave velocity, sediment compressibility, permeability and preconsolidation pressure. Results show that fracture geometry is mainly controlled by the degree of gas saturation and preconsolidation pressure. The damage level increases with the degree of gas saturation while the elastic modulus of sediments is degraded. Experimental data show that sediments do not entirely recover their original mechanical behavior when gas dissipates. Finally, the experimental data confirm that gas exsolution and expansion is a key mechanism for mud generation.

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