Study On The Environmental Impact Assessment Of Groundwater Of Ningdong Oilfield

Large scale of energy exploration will always cause a lot of adverse impacts to the local environment.Petroleum is one of the important standard energy used in our county,which brings huge economic benefits and meanwhile inevitably leads to a series of environment issues.As a key element of environment,groundwater has aroused great attention by governmental director and environmental researchers.How to exploit the energy rationally so that economic efficiency can be created and prevent the bad effects to the groundwater is a remarkable problem that should be considered seriously over the planning.The Ningdong Oilfield is located at the western edge of Ordos basin which is the prestigious cornucopia of China.Because of the dry climate,the region is covered by eolian-sand at the surface and brackish water is widely distributed.After working adequate researches and having a good understanding over the regional hydrogeologic conditions,the major aquifers of Ningdong Oilfield had been confirmed.The unconfined aquifer consists of Quaternary and Luohandong Formation—belonging to lower Cretaceous,while the confined aquifer consists of Huanhe Formation and Luohe Formation—belonging to lower Cretaceous.Considering the classification of the related assessment items,the groundwater assessment to the oilfield is rated as second-order of Class I.In order to have a grasp of the current situation,the high and low level as well as the quality of the groundwater environment had been detected and evaluated.To meet the requirements of the project planning and production,the future groundwater drawdown and effective radius had been calculated using the Dupuit equation.HYDRUS-1D was adopted to simulate the petroleum transportation through the un-saturated zone,while the GMS was applied to simulate the pollute characteristic factor such as COD's transportation through the saturated zone.According to the results of calculation,the target aquifer—Cretaceous confined aquifer is of big thickness and great water yield property that make it possible to provide enough water for the program and the groundwater flow field makes little change.Besides,the outcome of the petroleum transportation in un-saturated zone shows that the petroleum moves fast in the eolian-sand under accident condition,the eolian-sand performs strong adsorption capacities as well.During the service life of the oilfield,the petroleum is unable to infiltrate into the aquifer,but it will be sustained in the soil for a long time.The simulation results of pollutant diffusion in the saturated zone also figure out that the phenomenon of petroleum superscale could last ages and the petroleum could move a long distance during that time.Simulations for pollution leaking from multi-purpose station and wastewater disposal station turn out that pollutants(COD?ammonia nitrogen etc.)distance is short.The concentration of the pollutants diminish significantly and make little harm to the local aquifers and residents' wells.