Many data about methane hydrate presence in submarine and permafrost areas are received in during the last decades. It is significant that often gas hydrates don’t form bands, but situate in a porous space of dispersed sediments as porous cement similarly to ice-cement. As investigations shown, a gas content of these sediments may be enough considerable. In this connection, they can be regard as a source of a gas production.

　　It is necessary to know the thermodynamic conditions of gas hydrates decomposition in a porous space for technological problems solving.

　　Authors in a special pressure chamber have conducted physical simulation of hydrate decomposition processes in dispersed sediments. This allows influence of internal (sediments) and external (thermodynamic) factors on the P/T parameters of hydrate intensive decomposition in dispersed sediments to be estimated.

　　The analysis of the experimental data have shown an obvious shift of the P/T conditions of a hydrate intensive decomposition in the sediment porous space to the field of higher pressures and lower temperatures when compared to the system "water (ice) - free gas - gas hydrate" (P/Tg-w). This shift is not constant and it is growing with rise of the environment temperature.

　　Experimental results show that sediments grain size, mineral composition and salinity influence on the shift of the P/T conditions of the hydrate decomposition.

　　The researchers have been conducted both monomineral sediments (quartz sand, kaolinite and montmorillonite clays) and natural polymineral silt-sand-loamy composition sediments. Natural sediments were picked out of upper layers of permafrost where indications of hydrate content were fixed.

　　The experiments, which have been conducted on the model sediments show that the values of these shifts increase with growth of clay particles content and salinity and with change in the soil mineral composition following a trend from kaolinite clay to montmorillonite clay. It could be attributed to energy change of a porous water of sediments

　　The experiments which have been conducted on the natural sediments with natural humidity and salinity shown that the shift value of the P/T conditions of the methane hydrate intensive decomposition to average 1.6oC and 1 MPa in temperatures and pressure scales, accordingly.

　　These received data point necessity of the account of the sediments factor at estimation of natural gas hydrate decomposition in porous space of dispersed sediments.

　　The research presented in this paper has been partly funded by program of Russian Foundation for Basic Research № 01-05-64653.