Study On The Seepage Characteristics Of Rock Mass Of The Multiperiod Large Underground Storage Caverns

As an important fossil energy,oil is of great significance to the country ’s economic development and national defense security.In order to ensure energy security,China has carried out strategic oil reserves.As a more safe,economical and environmentally friendly oil storage method,groundwater-sealed oil caverns are the key development direction of oil storage at home and abroad.The selection of the address of the underground water-sealed cavern is demanding,and it is necessary to have a rock mass with good integrity,stable groundwater level and convenient transportation conditions.This requires full use of the appropriate project site selection,and it is difficult to excavate multiple caverns at one time,so it is necessary to construct large water-sealed oil caverns in stages.In the staged construction of large underground water-sealed oil and gas storage caverns,the new caverns may have adverse effects on the water seal stability of the similar caverns that have been put into operation,which may cause safety accidents such as oil and gas leakage in the operated caverns.However,there are few studies on this issue at home and abroad.Based on the background of a water-sealed oil cavern project in the third phase of a state reserve,through field investigation,data analysis,numerical simulation,induction and summary,this paper studies the influence of the distance between the two caverns and the water curtain level of the new cavern on the seepage field of the reservoir area,and the effect of setting up the vertical water curtain system between the two caverns.The main research results are as follows :(1)The operation data of the second-stage water-sealed oil caverns are analyzed,and the variation rules of borehole water level,cavern water inflow,water curtain replenishment and seepage water pressure are explored.The change of borehole water level is related to its location,most of which change dynamically in a small range and gradually decrease.The water inflow of the cavern decreases with the increase of operation time and gradually tends to be stable.The amount of water curtain replenishment fluctuates dynamically within a certain range and changes with regional precipitation.The safety range of seepage water pressure at most positions is similar and the change trend is similar,and the monitoring value in some places is small.The overall operation of the second phase cavern is in good condition.(2)Combined with the engineering geological and hydrogeological conditions of the reservoir area,the appropriate parameters are selected,and the hydrogeological model is established.The seepage field of the reservoir area under different distances and different water curtain conditions is simulated,and the changes of water inflow and water supplement of the reservoir are analyzed.When the distance between the two caverns is200 m and closer,the built second-stage caverns are greatly affected by the new caverns.When the liquid level of the water curtain system of the new cavern is 20 m,the influence of the new cavern on the existing cavern will be effectively reduced.With the decrease of the liquid level of the water curtain,the effect of the water curtain system will be reduced.When the liquid level of the new water curtain system is lower than 6m,the effect of the water curtain is not obvious.(3)The influence of vertical water curtain height and position on the seepage field of the two caverns is analyzed.The research shows that when the vertical water curtain height is 30 m,the influence on the seepage field of the two-stage cavern is not obvious,and the setting is of little significance.When the depth is 80 m,it can effectively isolate the adverse effects of the third-stage cavern on the second-stage cavern.When the vertical water curtain depth is deep,the position is located in the middle of the two-stage cavern,near the new cavern,and near the existing cavern,which can effectively play a role.However,when it is too close to the cavern,the water inflow of the adjacent cavern will be too large,and it is better to set it in the middle of the two-stage cavern.