一种新型除油机理及含油钻屑除油技术

油基钻井液是页岩气开发中最为常用的一种钻井液体系,随着页岩气勘探开发的加快发展及油基钻井液的大量使用,其产生的含油钻屑带来的环境污染也逐渐成为油气田企业的环保难题。为此,进行了现场含油钻屑组成、重金属含量和浸出液生物毒性分析,确定了含油钻屑污染特性和处理重点:针对含油钻屑污染特性,基于化学清洗法,首次引入过渡态理论,通过理论和实验分析,提出了一种新型岩屑除油机理,油滴从岩屑表面移动至油相存在着一个势能壁垒,清除岩屑中的油污需越过此势能壁垒;进而设计了含油钻屑除油配方,并通过单剂筛选、配方优化和除油条件优选,最终开发了一套含油钻屑化学清洗法除油技术。使用效果表明:在所研制的聚氧乙烯类除油剂与硫酸盐类、磺酸盐类辅助除油剂的共同作用下,势能壁垒可降低92.81%,由其处理的含油钻屑除油率达到93.02%。结论认为,该技术工艺安全简单、成本低、除油率高,可有效地解决含油钻屑的环境污染问题。

A new oil removal technology for oily drilling cuttings

Oil-based drilling fluid is one of the most common systems used in shale gas development. With the speeding up of shale gas exploration and development and the extensive application of oil-based drilling fluids, it is an environmental difficulty for oil and gas enterprises to deal with the environmental pollution caused by oily drilling cuttings. In this paper, the oily drilling cuttings were analyzed in terms of compositions, heavy metal content and leach solution biotoxicity, and accordingly the pollution characteristics and treatment focuses were determined. In view of the pollution characteristics of oily drilling cuttings, the transition state theory was introduced for the first time, based on the chemical cleaning method. A new cutting oil removal mechanism was proposed through theoretical and experimental analysis: an oil droplet has to move through a potential energy barrier before reaching the oil phase from the cutting surface, therefore, the potential energy barrier should be crossed so that the oil in the cuttings can be removed. Then, the oil removal formula for oily drilling cuttings was prepared. Finally, a set of oil removal technologies for oily drilling cuttings based on the chemical cleaning method was developed by means of single-dose screening, formula optimization and oil removal condition selection. It is indicated that by using the oil removing agents of polyoxyethylene and the auxiliary oil removing agents of sulphate and sulphonate, the potential energy barrier can be decreased by 96.8% and the oil removal rate of oily drilling cuttings is up to 93.02%. It is concluded that this technology is safe and simple with a low cost and a high oil removal rate, and it can solve effectively the environmental pollution caused by oily drilling cuttings.