Study On The Characteristics And Appropriateness Of Artificial Water-sealed Function For Underground Storage Cavern In Rainfall Area

The crude oil,known as “industrial blood”,plays an important role in the economic development of every country.Nowadays,the gap in oil reserves of China is large.The oil reserve situation of China is extremely severe.Compare to other storage ways,the underground water-sealed storage has the advantages of less land occupation,higher security and lower investment.Thus,the underground water-sealed storage has become the most preferred oil storage way in China.The water-sealed safety is a crucial factor to the success operation of storage system.And the artificial water-sealed function has been regarded as a necessary measurement for water-sealed safety.Thus,the study of water-sealed storage mainly focused on the water-sealed safety assessment with the function of water-sealed system.Meanwhile,the water-sealed safety is achieved by the synergistic effect of natural and artificial water-sealed(water curtain system)function.It is meaningful to focus on the separate function of artificial and natural water-sealed function to understand the synergistic mechanism of artificial watersealed function.In this study,some related engineering and scientific challenges was studied for water-sealed storage in the rainfall area of south China.The appropriateness of artificial water-sealed function was studied based on the synergistic mechanism of artificial water-sealed function.The main research contents and achievements were listed as follows:(1)Three new perspectives on the synergistic mechanism of artificial water-sealed function were proposed.Firstly,the synergistic mechanism of natural and artificial water-sealed function was proposed.It was pointed that the actual role of artificial function has always been ignored in the traditional design method.Instead,the attention has always been given to the water-sealed safety of storage system.Secondly,a new cognition of the relationship between water inflow and water-sealed function was proposed.It was pointed that the water inflow could reflect the degree of water-sealed function.Thirdly,the mechanism of artificial function under operation condition was proposed.It was pointed that the impoundment of access tunnel could have some influence to the water-sealed system and function.(2)An assessment method for the effect of water curtain system was proposed based on the time series analysis.Then,the assessment method was used in a certain large scale watersealed storage in Guangdong province of China.A phenomenon of inefficiency of water curtain system was found.And the rule of the inefficiency phenomenon was studied.Moreover,with the attention of seepage field variation caused by operation status,a phenomenon of excess water-sealed function under operation condition was found which has a performance of water inflow abnormal increase.And the reason of excess water-sealed function was investigated.(3)The optimization method about appropriateness of artificial water-sealed function was proposed based on the investigation of the above two phenomena(inefficiency of water curtain system and excess water-sealed function).On one hand,the optimization of water curtain system was proposed.To be specific,a new cognition was proposed for the action mode of artificial water curtain system.The new cognition was combined with the relationship between water injection volume and pressure of single water-curtain borehole.The assessment method for the result of injection experiment of single borehole was improved.Then,the optimization method for water curtain system was proposed comprehensively.On the other hand,optimization method for excess water-sealed phenomenon under operation condition was proposed.To be specific,the proposed method was aimed to refined use the impoundment phase of air tightness experiment as a large-scale in-situ experiment to check and optimize the excess water-sealed phenomenon under operation status.