近海地下石油储备库海水入侵风险研究

Study on the risk of seawater intrusion in offshore underground oil reserve

地下石油储备库于近海处建立,可降低石油运输成本,同时有较强的军事意义。但是临近海岸线,海水易入侵库区,导致库区内金属结构腐蚀,使储备库的使用年限降低。以某近海地下石油储备库工程为背景,构建了综合断层、节理密集带、导水通道等15种地质结构的精细化三维水文地质模型,研究了库区自然状态下和运行期的地下水渗流场及溶质运移场,模拟海水入侵风险。研究表明:(1)自然状态下地下石油储备库无海水入侵。(2)运行期只在洞库顶部以上25m处设置四周超出洞室50m、水幕孔间距为10m、孔径0.11m的水平水幕时,不能有效防治海水入侵。(3)洞库运行9 a时,3#洞室东南侧Cl-物质的量浓度超过7 mol/m^(3),海水开始入侵洞室群;运行22~23 a时,海水入侵速率最快;运行41a时,3#洞室东南侧Cl-物质的量浓度超过143 mol/m^(3),海水入侵达到对钢筋的强腐蚀程度;运行50 a时,除1#洞室外其余所有洞室均受到海水入侵,3#、4#洞室有部分区域达到强腐蚀程度,海水入侵最严重。建议增设垂直水幕等设施,以增强对海水入侵的防治。研究成果可为近海地区地下石油储备库抑制海水入侵提供借鉴。

Underground oil reserves are established near the sea,which can reduce the cost of oil transportation and have strong military significance.However,the proximity to the coastline makes it easy for seawater to intrude into the reservoir area,resulting in corrosion of the metal structure in the reservoir area,thus reducing the service life of the reservoir.A simulation study on the risk of seawater intrusion was carried out with an offshore underground oil reserve project as the background.A refined three dimensional hydrogeological model with 15 geological structures such as integrated faults,jointed dense zones and water conduction channels was constructed,and the groundwater seepage field and solute transport field in the reservoir area under the natural state and during the operation period were studied.The study shows that(1)there is no seawater intrusion in the undergroundoilreserve in the natural state.(2)During the operation period,a horizontal water curtain with a distance of 10 m and a diameter of 0.11 m was only set at 25 m above the top of the cavern reservoir,exceeding the cave by 50 m around,which could not effectively prevent seawater intrusion.(3)When the cave reservoir was running for 9 a,the Cl−mole concentration on the southeast side of 3#cavern room exceeded 7 mol/m3,and seawater began to invade the cavern group;when it was running for 22 a to 23 a,the seawater invasion speed was the fastest;when it was running for 41 a,the Cl−mole concentration on the southeast side of 3#cavern room exceeded 143 mol/m3,and the seawater invasion reached the strong corrosion degree of steel;when it was running for 50 a,all the cavern rooms except 1#cavern room were invaded by seawater,3#and 4#cavity rooms have some areas to reach strong corrosion degree,seawater invasion is the most serious.It is suggested to set up additional facilities such as vertical water curtain to enhance the prevention and control of seawater intrusion.The research results can provide reference for the suppression of seawater intrusion in underground oil reserves in offshore areas.