浅析某油田地下水石油类污染途径

研究区处于东北某油田区,该油田已有近50年的开发历史。随着对石油需求的不断增加,大量的石油被开采了出来。但是在开采过程中由于对落地原油及开采过程中油田废水的处置不当,致使地下水遭受了污染。因此保护地下水免受进一步污染对当地居民的身体健康和人身安全都是非常必要的。笔者基于研究区水样测试的结果石油类污染物浓度等值线图,发现地下水中石油类污染小范围内呈面状分布外,主要呈点状分布于研究区。通过结合对研究区地质环境、构造背景、地表水流和污染源的大量调查研究,分析得出石油类污染物主要是通过由过量开采地下水引起的地裂缝和新构造断裂引发的地裂缝以及事故性污染到达地下水的。研究区的ZK6号井附近由于长期的超量开采地下水从而改变了地下水流向,在地表则形成了地面沉降并引发了此处的地裂缝,致使此地下水油类的污染非常严重。另外,新构造断裂在北西向、北北东向及东西向3组壳断裂带的基础上继承性运动,致使下伏含油层油气沿裂缝上窜污染上覆含水层,同时在油田地表发育大量的地沟、地裂缝,地表洒落的原油及其他污染物通过这些地裂缝污染含水层。

Ways of groundwater pollution by oil in an oilfield

The study area belongs to an oilfield in Northeast China and the development of the oilfield has a history of nearly 50 years.With increasing demand for oil,vast amount of oil has been exploited.However,during exploitation,groundwater was polluted because of spilled oil and wastewater in this oilfield.Therefore,protecting groundwater from further pollution is essential to the health and safety of citizens in the oilfield.Based on an analysis of water samples,the authors have compiled a contour diagram of oil pollutant concentrations in groundwater in the study area and found that,except in a small scope where oil pollutants are distributed areally,most oil pollutants are distributed as patches in the study area.The contour diagram of oil pollutant concentrations,combined with substantial investigation and research on the geologic environment,structural setting,surface water flow and possible surface polluting source of the study,suggests that the oil pollutants mainly moved into groundwater by accidental pollution and ground cracks produced by over-development of groundwater and neotectonic fracturing.Due to long-continued over-pumping of groundwater near hole ZK6 in the study area,the direction of groundwater changed,and ground subsidence occurred and many ground cracks appeared at the surface;so groundwater pollution by oil is very serious.In addition,neotectonic faults inherited the NW,NNE and E-W sets of crustal faults,thus causing oil/gas in the underlying oil layers to move up along the fractures and pollute the overlying aquifers.Furthermore,large numbers of ground channels and ground cracks formed at the surface,and spilled oil and other pollutants polluted the aquifers through them.