Evaluation Of Damage To Marine Ecological Environment By Offshore Oil And Gas Development Engineering

Offshore oil and gas resources are an important part of China's energy structure,accounting for nearly 30% of total oil and gas reserves in China.The development of offshore oil and gas resources effectively safeguards the country's energy security.Offshore oil and gas exploitation engineering will inevitably bring about problems of marine environmental pollution,and damages to the marine ecological environment.In particular,pollutants emitted during the production phase of oil and gas development may lead to continual damages to the marine ecological environment.While limitations exist in the current researches concerning the impact of offshore oil production on the marine ecological environment,the content of research is not comprehensive,and the method of research lacks of long-term positive research.In addition,there is a lack of researches concerning the evaluation on the damages to marine ecological environment due to the production water discharge from offshore oil platforms.Therefore it is of great practical significance and pertinence to carry out the evaluation on the damages to marine ecological environment due to the produced water discharge from offshore oil development projects.This article mainly focuses on oil & gas exploitation projects in the WeiZhou sea area which located in Beibu Gulf.By means of comprehensive use of environmental engineering,marine ecology,offshore oil and gas development engineering and mathematical methods etc.,analysis and studies are respectively made on such aspects as the characteristics of pollutant production from offshore oil & gas development engineering,the evolution of ecological environment in WeiZhou sea area,impact on the marine ecological environment due to oil & gas development,the evaluation model for ecosystem damages due to production water discharge,as well as the effectiveness of present environmental protection measures etc.By coordinating and analysing the marine environmental data and material obtained during the site surveys carried out over the recent two decades in the WeiZhou area,and using correlation analysis,interrelationship is analyzed for the ecological environment changes in the sea area due to offshore oil exploitation development,and the main contributing factors are screened by algorithm establishment which influence on the marine ecological environment.An evaluation index system is designed for the damages to the marine ecological environment on the basis of a “pressure-state-response” evaluation framework,thus to evaluate the damages to the marine ecological environment caused by the production water discharge from oil and gas production platforms.The main research results of this article include:(1)By analyzing the pollutant generation links and the characteristic pollutants discharged from offshore oil and gas development engineering,and using principal component analysis and correlation analysis,the major contributors to influence the changes on marine ecological environment due to oil and gas development engineering are selected,which include DO,SS,PO4-P,Cd and Volatile phenols in sea water;As,Zn and Cr in Sediment;diversity and uniformity of Phytoplankton and Zooplankton,Benthic biomass,and Cr content in fishes.(2)Based on the characteristics of oil & gas development engineering and "Pressure-State-Response" framework,an evaluation model and evaluation index system are established for the damages to marine ecological environment due to production water discharge from oil & gas development engineering.The model is compared with the integrated index method for environmental quality to verify its effectiveness and applicability.(3)Calculated by the damage evaluation model,the conventional conclusion is verified that production water discharge significantly affects the marine ecology within the sea area 500 m away from production water outlet.Meanwhile,it is found that the scope of damages features seasonal variation and can extend to the sea area 1000 m or less away from the outlet.This paper screens by positive analysis the main factors that influence the marine environment in oil and gas development,and builds an evaluation model based on this.Based on the strength of oil and gas development activities and changes in the marine environment,quick evaluation can be made on the damages to marine ecological environment due to oil and gas development activities with a few indicators,and the scope of marine environmental impact and seasonal variation characteristics can be assessed more accurately.The evaluation model built in this paper expands the current methodology which is mainly used for determining the impact area by means of the pollutant diffusion model,and provides a new evaluation method for practical work.