Pozzolanic activity and environmental risk assessment of water-based drilling cuttings of shale gas

Abstract

• The pozzolanic activity of WDC was comprehensively studied. • A systematic study of human carcinogenic risk and ecological security risk assessment were carried out. • The risk control values of heavy metals were presented In order to evaluate the application potential of water-based drilling cuttings (WDC) as cementitious materials for building material admixtures, the physical and chemical properties of WDC were studied, and the environmental risk and human health risk of heavy metals in WDC were also systematically studied. The results showed that the particle pitch diameter is 26.70 µm, mineral types of WDC are mainly limestone, calcium hydroxide and quartz. The 28-day compressive strength of WDC is 27.6 MPa. The strength activity index of WDC cement mortar is 58.3 %, and the amorphous phase content is 23 %. At 80 °C, the weight loss rate and bound water content of “ WDC-CaO-H 2 O ” hydrate were 5 % and 0.13, respectively. It is found that WDC has certain pozzolanic activity, can not only participate in the secondary reaction of the system as active mineral admixtures, but also reduce harmful holes in the system by filling compaction. According to the calculation and analysis, only Hg reached moderate pollution in WDC, As and Cr had carcinogenic risks to human health, so Hg, As and Cr were used as characteristic heavy metal pollutants in WDC. As well as, under the analysis results of characteristic heavy metals and the limits of relevant standards, the risk control values of heavy metals in different exposure scenarios were obtained. The expected existence of arsenic ions, chromium ions and mercury ions in XPS spectra and their corresponding binding energy and orbital state were analyzed. After analysis and fitting, these values are basically consistent with the reference values cited in the document, and the resource utilization direction and environmental safety control measures of WDC were proposed. The above research results will further promote the basic technical support of shale gas WDC resource utilization, and ensure the ecological environment safety and human health safety in the process of resource utilization.