Study On The Preservation Condition Of Shale Gas In The Lower Cambrian Niutitang Formation In Suiyang-Fenggang Block

Shale gas as an unconventional petroleum has been got more and more concerns.There are some wells of Niutitang formation do not succeed in Guizhou Province.Compared to North America,The Yantze platform suffered a lot of tectonic movements.Researchers realized that well preservation condition is the key to commercial exploration.The Lower Cambrian Niutitang Formation in SuiyangFenggang block is the research object of this theme.The research based on the characterize of physical properties and tectonic,the influence of various factors on the preservation conditions was analyzed and the diffusion mode of shale gas in Niutitang Formation was summarizedThe mineral composition of the shale of the Niututang Formation,which controlled by sedimentary facies,is mainly composed of quartz,clay and feldspar.The shale has numerous quartz and feldspar,and small clay.The characteristic on vertical zonation is increasing quartz and reducing clay.The brittleness index calculated by mineral composition ranges from 38.1% to 97.7%,average 62.2%.The index is increasing with depth.The rock with strong brittleness has higher Young modulus and lower Poisson's ratio,as the result,the preservation is broken.The high thermal evolution reduces the number of organic holes,then,the storage space of shale gas is reduced.There are three synclines and three anticlines in the research area.The tectonic intensity is increasing from west to east.In Wanglong anticline,the tectonic intensity is increasing from north to south.There are three period fault in the area.The strike slip fault is the latest fault,and it does not break the deep formation showing from the geological section.The Burial history type attribute to early bury and later uplift.The timing of uplift was about 110 Ma ago.The present burial depth of Niutitang formation is 900-5000 m.The open environment is indicated by the lower formation pressure gradient.The unconformity under the Niutitang formation cause the Niutitang formation do not have a sealing baseboard.The preservation condition is effected by all of this.The hydrocarbon was diffused from the source rock and the remaining hydrocarbon decrease.The diffusion direction of the shale gas move along the bedding and move to bottom.There are many fractures nearby the fault.The pressure is lower and the permeability is higher,and the intensity of diffusion is increasing.In the research area,syncline has better caprock and smaller uplift amplitude,so the preservation condition of syncline is better.