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伴随油气开采总量的提升,钻探所需处理剂的成分越来越复杂,油田产生的废弃物也随之增多,其中的化学处理剂、重金属离子、石油类物质、高浓度无机盐是主要的污染源,会对生物、土壤以及水体造成严重污染[1-2]。目前,钻井废弃物常用的处理方法包括回填处理[3]、土地耕种[4]、填埋[5]和固化处理[6]等。其中,固化处理技术研究广泛并已应用于现场实践,但仍存在一些问题。在固化过程中,油、可溶性盐等污染物与固化材料并不发生反应,只是实现物理密封,存在污染物的迁移和二次浸出污染问题;同时,固化废物具有环境适应性和耐久性问题,用于井场施工的固化钻井废弃物长期暴露在水侵、酸碱腐蚀等恶劣环境下,强度会逐渐降低,结构出现松动,将失去其作为路基材料或建筑材料的基础[7]。而材料、建筑领域的表面涂覆技术作为一种表面改性工艺,能够改变表面润湿性能,强化表面强度,保护被涂覆物的理化性能稳定[7-10],可以对固化物进行有效的封固。
为此,本研究综合考虑固化物强度和污染物浸出等问题,提出钻井固化废弃物表面涂覆技术,优选表面涂覆工艺,对最佳涂覆配方进行了效果评价和机理分析,为有效地防止固化物二次浸出污染、提高固化物的环境相容性提供了参考。
钻井固化废弃物表面涂覆工艺的正交实验优化及效果评价
Orthogonal experiment optimization and effect evaluation of surface coating on solidified drilling waste materials
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摘要: 针对钻井废弃物固化处理之后存在的二次浸出污染问题,通过正交实验优化,得到一种钻井废弃物表面涂覆技术,采用吸水率测试仪、接触角测量仪、扫描电子显微镜、红外光谱仪等仪器对涂覆固化物的防水性能、环保性能和耐久性能进行测试,并对涂覆层微观结构进行分析,进一步探究其作用机理。结果表明:钻井废弃物经涂覆后,吸水率为3.04%,表面接触角为79.56°,表现出良好的防水性;浸出液化学需氧量达到国家一级标准,固化处理未能全部封固的Cd、Mn以及其他重金属离子均未检出,具备良好的环境相容性;浸泡在10% HCl和10% H2SO4溶液环境下7 d强度损失率均小于50%,耐水、耐酸性较强。微观结构显示涂覆材料能够渗入废弃物的孔隙结构中,在废弃物表面形成密闭的疏水层,所以表面涂覆技术能够显著提高钻井废弃物的环保性能和耐久性,初步体现资源化利用价值。Abstract: In order to solve the problems of the secondary leaching pollution after the solidification treatment of the drilling wastes, a surface coating technology was obtained through the orthogonal experiment optimization. The water absorption, contact angle, scanning electron microscope, infrared spectrometer and other methods were carried out to investigate the waterproof performance, environmental protection performance and durability performance. The microstructure of the coating layer was analyzed to further explore its mechanism. Results showed that the coated drilling wastes indicated a well waterproof performance with the water absorption rate of 3.04% and the surface contact angle of 79.56°. The COD value of the leaching solution reached the PRC national Grade I discharging standard. Meanwhile, the Cd, Mn and other heavy metal ions without completely sealing by the curing treatment were not detected, thus showing a good environmental performance. After soaking in the 10% HCl and 10% H2SO4 solution, the 7-days strength loss rate of the coated drilling wastes was less than 50%. The microstructure showed that the coating material penetrated into the pore structure of the wastes and formed a closed hydrophobic layer on its surface. Therefore, the surface coating technology can significantly improve the environmental performance and durability of the drilling wastes, indicating a value of resource utilization.
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表 1 涂覆固化物浸出毒性测试结果
名称 化学需氧量/mg·L−1 色度/倍 浊度/FTU pH 重金属离子含量/mg·L−1 Ni Cd Cu Pb Zn Cr Mn 钻井废弃物 548.5 600 735.0 9.5 1.7 2.4 77 - 17 28 1.8 固化废弃物 96.0 10 24.81 7.0 - 0.001 0 - - - - 0.007 2 涂覆固化物 50.7 2 9.96 7.0 - - - - - - - 一级标准 ≤100 ≤50 ≤70 6~9 ≤5 ≤1.0 ≤100 ≤5 ≤100 ≤15 ≤2.0 二级标准 ≤150 ≤80 ≤150 6~9 ≤5 ≤1.0 ≤100 ≤5 ≤100 ≤15 ≤2.0 注:“—”表示浓度低于仪器最低检测限度。 -
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