Research On Distribution Characteristics And Pollution Evaluation Of Heavy Metals In Abandoned Drilling Mud In Oil Field

Large-scale exploration and development of the domestic oil resources is harmful to the environment, and also bring enormous pressure to work of environmental governance field. In this paper, as a case the north area of Tarim Oilfield, we proceed with a large amount of waste emissions from oil drilling mud.Drilling mud is consist of a variety of raw materials and chemical additives dispositions during exploration, drilling, mining and other process, it’s a necessary fluid circulation for required drilling with its variety of functions. As the name suggests, the abandoned drilling mud refers to the mud which can’t meet the technical requirements of crafts during the drilling process or the drilling mud discarded in the drilling fluid circulation tank after completion of the drilling fluid, as well as the drilling mud which is spilled at the well site in the construction process for other reasons.First, I list the main types and materials of drilling mud briefly, and its harm on environment. Secondly, this paper analyzes the nature of the heavy metal in these waste drilling mud, also the soil background values surrounding these researched wells; and then according the test results of drilling mud, describe the eight kinds of content features of heavy metals in the leachate contaminants of drilling mud. Meanwhile discuss the conversion of each index between the former and the later. Then comes to the detection of indicators of pollution and the pollution levels of 14 wells in the area through single factor evaluation method and the N.L. NEMEROW. Finally, combining existing treatments for drilling mud in The Tarim Oilfield, I made several management strategies for the waste water-based drilling mud. The conclusions as follows.(1) The spatial distribution of heavy metals in the drilling mud in study areaDistribution on the plane:the distribution of eight heavy metals on the plane show three categories, that are "Descending distribution", "Unimodal distribution", "Binmodal distribution ". Where concentrations of heavy metals in zone1, zone 3 and zone 5 are high-value areas, zone 2 and zone 4 are low-value areas.Distribution in the vertical: the distribution of heavy metals in the vertical is also present three trends in the study area, which are "Descending distribution", "C-type", and "opposite C-type". The distribution belongs to the first include Hg、Cd、As, then the distribution belongs to the "C-type" include Pb、Ni, at last, Zn、Cu、Cr show "opposite C-type" 。(2)Pollution Assessment conclusion on Heavy Metal in the abandoned drilling mud of Study area:Evaluation for single factor : Pb、Zn、Cu、Cr、Ni are over the standard value but Hg、Cd、As, and the single factor index of them descend as follows: Cr> Zn >Ni> Pb >Cu; the Excessive rate of Cr is highest among all the heavy metals, reach to 28%, and for the whole study area, the Pollution share ratio of 8 heavy metals descend as follows: Cr>Zn>Ni>Pb>Cu>As>Cd>Hg; in the end, we got the conclusion that Cr、Zn、Ni、Pb are the main pollutants and 6#、11#、5# are the main polluters by the road of Equal Standard Pollution Load.Evaluation for The N.L.Nemerow: among the 14 wells, 6#、11#、5#、14# are severely polluted, and 8# is slightly polluted, all the rest wells are clean or yet.