Study On Ecological Impact Assessment Of Oil Shale’s Different Exploitation Means

At present, the world’s oil and gas supply is tight and the international oil price keepsrising. To face the high international oil price and China’s strong demand for energy, thestrategy of oil shale exploration has come into vision. Jilin Province owns rich oil shaleresource, which ranks first among other provinces in China. The proven reserve of oilshale in Jilin Province is about1.712trillion tons, accounting for55.5%of the total inChina. As a result, Fuyu in Songyuan City in Jilin Province was chosen as the oil shalemining technology research area.Oil shale are developed usually by two ways, which are open-pit mining andunderground mining, for oil refining and power generation. Open-pit mining causesserious damage to the ecological environment and which could not be avoided. And alarge amount of “three wastes” are produced during the dry and distillation process on theground, which means serious pollution of the environment, and endanger the humanproduction and life. In recent years, the underground mining techonology was widespreadconcerned for its high oil utilization. However, in the heating process, the long-chainhydrocarbons in oil shale will be broken, producing a range of different molecular weightorganic compounds, which include volatile organic compounds (benzene, toluene,ethylbenzene, xylene) and semi-volatile substances (compounds such as phenol, anilineand pyridine, etc.). These toxic substances pose a serious threat to the soil and waterquality and ecological safety. In addition, the use of underground mining technology isbound to undermine the thermodynamic equilibrium and stress balance of theunderground environment, and may cause oil shale rock deformation, resulting in newenvironment geologic effects. At present, there is no large-scale application of the oilshale underground mining technology, therefore, the ecological impact assessment andenvironmental protection measures aimed at the pollutions caused by this technology arenot carried out yet. And abroad researches on this area are rarely reported.In this paper, the processes of these two oil shale mining methods were analyzed todetermine the contamination characteristics of open-pit mining technology and underground mining technology. Based on what mentioned above, the eco-environmentalquality evaluation index system was established, which contained18indicators in5categories. After the eco-environmental quality evaluation system was determined, theanalytic hierarchy process was chosen to analyse the weight of each indicator. On thisbasis, the software yaahp Version0.5.2was applied to compute the weight of the variouseco-environmental quality indicators in the evaluation. Vegetation coverage indexoccupies the highest weight,0.2783; followed by the index of water resources,0.2371;then the third one–the index of biological abundance,0.1792. And the index of landdegradation, the index of environmental quality have the the minimum weight, both0.1527. Finally, quantitative Assessment and forecast of the ecological environment instudy area was carried out according to the established index system and the set weight ofeach indicator. EI of the study area at present is0.5057, indicating that the state of thecological enrironment is all right. If the open-pit mining technology is chosen for thedevelop of the oil shale, the△EI will be-0.0818, which means the ecologicalenvironment is obviously deteriorated. On the opposite, if the underground miningtechnology is chosen,△EI will be-0.053, significantly lower than the former, whichmeans the degradation of the ecological environment using this technology in the studyarea is much lower than the former. What need to be emphasized is that the use ofunderground mining technology is bound to undermine the thermodynamic equilibriumand stress balance of the underground environment, and may cause oil shale rockdeformation, resulting in new environment geologic effects. Due to the lack of thecorresponding study of the geological effects, the prediction and evaluation of the contentis not taken into account in this paper. If the research on the geological effects caused bythe underground mining could support the evaluation in the future, these content shouldbe focused on in the ecological impact assessment.