ROCK MECHANIC CHARACTERISTICS OF GYPSUM COVER AND CONSERVATION FUNCTION TO GAS IN THE KUCHE DEPRESSION, THE TARIM BASIN

Rock mechanic characteristics of the Tertiary gypsum cover in the north of Kuche depression is analyzed based on simulation experiment.Plaster rock,salt rock and mudstone are plastic material and have the ability of plastic deformation.Creeping shows that the Tertiary gypsum cover has strong fluidity.Plastic flow appears if the gypsum cover suffers tectonic stress.Under the influence of fault,the gypsum cover usually forms huge gypsum-mud cover tectonic trap,which is compact with high expulsion and pore fluid pressure so as to be good cover.Most of fractures and detachment fractures are formed by gypsum-mud rock creeping.And there are huge fracture groups filled with ooze in fracture zone,which have excellent enclosing function and hold gas back effectively.