The Identification Method And Application Of Advantage Seepage Channel In Surrounding Rock Of Underground Oil Storage Caverns

The underground water-sealed oil storage cavern was first built in Sweden.It has the advantages of small land occupation,high safety,short construction period and large reserve,making it becoming the first choice of oil reserves.It is the key to ensure water sealing in the oil storage of the underground water depot.But the existence of the advantage seepage channel in the surrounding rock will form a draining area above the cavern,which affects the water sealing and causes the leakage of the oil.On the other hand,the water inflow of the caverns and the operating cost will be increased.However,the seepage mode of underground water sealed oil storage is complex.It is very difficult for the data in the exploration stage to have a complete understanding of the seepage path.Therefore,in this paper,a method of identifying the advantage seepage channel is proposed by using the data of fracture distribution and the connectivity of water curtain before the excavation of the cavern.Based on the project of underground water-sealed oil storage in Guangdong province,this paper analyzes the geometric parameters and distribution rules of jointed rock joints in the reservoir area.Establishing a three-dimensional random fracture model according to the characteristics of different zoning fissure,Analysing the permeation characteristics of the dominant seepage channel through the simulated water curtain test,And puting forward the superiority seepage of the water curtain layer.The high seepage hole discrimination standard of flow channel and the location of high permeability hole are determined,and the advantage seepage channel in the reservoir area is found according to the law of fracture distribution.Finally,the position of the advantage seepage channel is verified by the results of transient electromagnetic test and the seepage point statistics of the main cavern.The main research contents and results are as follows:(1)The type and distribution of groundwater in the reservoir site are studied and the permeability coefficient of the fractured rock mass is analyzed through hydrogeological survey and drilling hydrogeological test.The structure surface collection and reading of the water curtain borehole imaging data are carried out to study the geometry of the joint distribution in the water curtain layer(the geometry of the spacing,inclination,and inclination angle).(2)Based on the statistical characteristics of the geometric elements of the fissure,the three-dimensional stochastic fracture network model of each area of the water curtain is established.The test process of the effectiveness of the water curtain is simulated,and the seepage law of the dominant percolation channel is analyzed.(3)Based on the seepage law of rock mass,the relationship between the pressure of water curtain hole obtained by numerical simulation is piecewise function fitting,and the criterion of large flow,high permeability and osmotic convergence for the position of the dominant percolation channel is established by using the fitting results and combined with the results of the water curtain connectivity test,to identify the position of the high permeability hole.The position of dominant seepage channel is deduced according to fracture inclination and dip angle.(4)The results of the transient electromagnetic test and the seepage data of the main chamber are verified by the results of the identification of the dominant seepage channel.