水基钻屑固化填埋对土壤环境影响变化趋势研究

On changing trend of the effect of water-based drilling cutting solidification landfill on soil environment

为了解水基钻屑固化填埋池周围土壤环境质量现状,以西南某页岩气田为例,选取了3个典型井场的水基钻屑固化填埋池,先对水基钻屑固化原料成分、固化机理、固化效果进行了分析,再对池体上覆土壤和周边土壤进行长期定位监测,最后采用内梅罗指数法对土壤重金属污染状况进行综合评价,并分析了水基钻屑固化填埋池土壤重金属综合污染指数变化趋势。结果表明,水基钻屑呈碱性,含有一定量的重金属及石油类,采用水泥和粉煤灰对水基钻屑进行现场固化,固化体抗压强度可达0. 65 MPa,浸出液满足GB 8978—1996《污水综合排放标准》一级排放标准,水基钻屑固化效果较好。经过2a的水基钻屑固化填埋池土壤跟踪监测,与土壤背景值相比,水基钻屑固化填埋池上覆土壤和周边土壤Cd、Hg、Cr及石油类质量比均随着时间呈现波动变化,但是土壤各项监测指标均未超标; 3个井场的水基钻屑固化填埋池上覆土壤重金属综合污染指数分别为0. 42-0. 54、0. 47-0. 53、0. 33-0. 56,周边土壤重金属综合污染指数分别为0. 45-0. 64、0. 48-0. 66、0. 29-0. 51,土壤重金属综合污染指数均小于0. 7。水基钻屑固化填埋短期内对周围土壤环境影响较小,长期可能会增加土壤的潜在环境风险。

The present paper is to devote itself to an investigation of the overlying and surrounding soil of the water-based drilling cutting solidification landfill. To achieve the purpose, we have made an analysis of the composition of the cutting, its mechanism and effect of such water-based drilling cutting through a series of long-term stationary experiments. In order to identify and determine the status-in-situ of the soil environmental quality around the waterased drilling cutting solidification landfill, we have done experiments concerned with the 3 representative water-based drilling cutting solidification landfills by taking a platform of the shale gas field in the southwest of the said environmental location as a case study sample. Furthermore, we have also analyzed the changing trend of heavy metal composite pollution index of the soil with Nemerow index. The results of our investigation show that the water-based drilling cuttings are alkaline, consisting of some content rate of heavy metals and oil grease. And the cement and fly-ash prove to be effective in disposing the water-based drilling cuttings through solidification, whose compressive strength can be expected to reach O. 65 MPa, with its lixivium being within the permitted level for the first grade standard of GB 8978--1996, that is to say, the solidification effect proves to be well enough. As a result of 2 years＇ tracking monitoring, the fluctuation has been found with time in the content of Cd, Hg, Cr and petroleum of the overlying and surrounding soil compared to its background value, with no soil monitoring indicators beyond the standard. On the contrary, the calculation has been done, indicating that the comprehensive pollution index of the overlying soil heavy metals remains in the range of O. 42 - 0. 54, O. 47 - 0. 53 and 0. 33 - 0. 56, respectively, with those of surrounding soil being 0.45 - O. 64, 0.48 - 0. 66 and 0. 29 - 0. 51, respectively and correspondingly. And, luckily enough, the comprehensive soil heavy metal pollution indexes turn out to be all less than O. 7, which means that, in a short term, it wouldn＇ t bring any unfavorable influence on the surrounding environmental soil, though, it remains likely to bring potential risk to the soil in the long run.