Evolution of Permafrost and of Gas Hydrate Stability Zone

Abstract

In this chapter, permafrost modeling is analyzed as a part of procedure of basin modeling. The temperature on the basin surface corresponded to variations in paleoclimate is taken into consideration beginning with the time of the basin initiation and including the past 3.4 Ma, when formation and degradation of permafrost were repeated many times. The use of real lithological composition of sedimentary rocks distinguishes this approach from previous studies of permafrost evolution. Depth and time variations in thermophysical parameters of rocks (heat conductivity, heat capacity, unfrozen water and salt content, porosity) had a considerable influence on the results of modeling. The calculations demonstrate that the formation and degradation of the zones of stable existence of gas hydrates in the Pliocene-Holocene time are in close correlation with the events of formation and degradation of permafrost layers. All of these events were repeated many times during the Quaternary (Chap. 10). Section 9.3 considers the principles for determining of the base and top of the zones of gas hydrate stability and analyzes the conditions of stable existence of gas hydrates in the land and marine environments.