Characteristics Of Hydrate Reservoir And Vertical Stability Zone In The Northeast Of Qiangtang Basin

The natural gas hydrate in permafrost area is closely related to the thickness of tjaele.Compared with conventional oil-gas reservoirs,the determinants of hydrate form preservation are temperature,confining pressure and reservoir space.The large-scaled permafrost in the northeastern part of Qiangtang basin fully meets the requirement for the formation of natural gas hydrate.In this paper,I chose the hydrate in the frozen-soil area of northeastern Qiangtang as the study object,and the Wuli and Tumen regions in northeastern Qiangtang were picked out as the research area.Based on the theory of petrology,sedimentology,petroleum geology,logging geology and experimental chemistry,the data of the study area,core,slice,logging and scanning electron microscopy were collected for analyzing the strata,sedimentary facies and Reservoir characteristics in research area.Finally,based on my high carbon dioxide hydrate synthesis-decomposition experiment,I studied the vertical stabilization zone of hydrate reservoir in northeastern Qiangtang.The following results were listed below:1.The sedimentary facies of the main reservoir rocks in the upper Permian to middle Jurassic groups in the permafrost region of the northeastern Qiangtang area are river-lacustrine facies,coastal delta facies,coastal-shallow marine facies,semi-confined bays phase and carbonate facies.Amongst these,the reservoirs of carbonate facies and coastal delta facies are most developed2.Based on the reservoir analysis of permafrost hydrate,a special type of hydrate reservoir was introduced in this paper.In my opinion,besides the pore type and fractured reservoir,there is a special type of reservoir called Sediment type reservoir.According to the pore-permeability characteristics of reservoir rocks in the study area,it can be divided into structural reservoirs and lithologic reservoirs.The structure reservoirs are the most important reservoirs in permafrost areas.Lithologic reservoirs are the prevailing reservoir in the study area.According to the reservoir clustering analysis,the reservoir types in the study area can be divided into?type?favorable?and?type?more favorable?reservoirs.The upper Permian Na Yixiong formation sandstone reservoir belongs to class ? type and class ? type reservoir,Duo Gaila and Que Mocuo sandstone reservoirs belong to class?and ? reservoirs.The Bu Qu reservoirs are group ? reservoirs.3.Low-temperature and high-pressure experiment:multi-step heating dissociation method of hydrate in the simulation of her frozen soil hydrate temperature-pressure field,gas composition,formation water,such as physical and chemical conditions,hydrate stable temperature range is 274.07 K to 274.07 K,what corresponding the logging temperature-depth range is 40-520m.4.According to the drilling data of Wuli area,the geothermal field in the study area presents a negative relativity between temperature and depth.According to my own research,the vertical stability zone of the hydrate experiment is 40-520m below the surface.However,the deviation still occurred in the depth of 597m for technical reasons.After the compromised deviation,I reckon that the bottom plate of the vertical stabilization zone exists near 560m underground.Therefore,the research and production of CO₂ hydrate can be widely performed in the horizon between 40m⁵60m underground.