Abstract: The Waste Oil-Based Drilling Fluids (WOBDF: 8#, 10# and 20#) from drilling platform in Nanhai Oilfield have high solid content, viscosity and density, and are difficult to be recovered, transported and recycled. The on-site use of high-speed centrifugation and thermal desorption methods cannot meet the requirement for the solid content in WOBDF, and conventional flocculants also cannot effectively remove harmful solid particles from WOBDF. In this paper, tetraethyl silicate and nano-Fe₃O₄ were used as raw materials, and methyl acrylate was used as graft monomer to prepare magnetic nano-cores. Then Michael addition reaction was carried out with 1,3-propanediamine and triethylenetetramine, respectively. Thus, two flocculants with magnetic cores and hyperbranched structures were successfully prepared (with 1,3-propanediamine as the end capping agent for flocculant-1, with triethylenetetramine as the end capping agent for flocculant-2). The molecular structures of the flocculants were determined by FT-IR and elemental analysis. Then, the coagulation centrifugation method was used to investigate the effects of two types of hyperbranched coagulants on the solid content, density, and viscosity of WOBDF. The results show that when the dosage of flocculant is 2.5wt%, the harmful solid removal rates of flocculant-1 for 8#, 10# and 20# drilling fluids are 82.75%, 62.30% and 70.56% respectively, and the solid content of 8#, 10# and 20# drilling fluids after treatment is was 5.21%, 15.34%, and 14.43%. The removal rates of harmful solids from 8#, 10# and 20# drilling fluids by flocculant-2 are 81.06%, 59.13% and 69.48% respectively, and the solid content of 8#, 10# and 20# drilling fluids after treatment is 5.72%, 16.63% and 14.96% respectively. After treatment, the densities of the three drilling fluids are 0.86~1.16 g·cm^-3; The apparent viscosity and plastic viscosity are 52~90 mPa·s. The flocculation mechanism is related to the adsorption performance of its hyperbranched molecular structure besides charge neutralization and adsorption bridging. The treated WOBDF meets the requirements of drilling platform for offshore waste drilling fluid: the solid index of 8# drilling fluid (which has been thermal desorptioned) is 5%~7%, and the solid index of 10# drilling fluid and 20# drilling fluid (which has not been treated) is 10%~18%, which provides technical methods for the treatment of other WOBDF.

Key words: waste oil-based drilling fluid, flocculant, harmful solid phase, cationic polyamines, hyperbranched structure

摘要： 南海油田某钻井平台产生的废弃油基钻井液(8#、10#和20#))固相含量高、粘度高、密度大,并且存在回收、转运困难和难以循环使用的问题。现场采用高速离心和热脱附的方法均不能降低废弃钻井液中固相含量,且使用常规的絮凝剂也不能有效去除废弃钻井液中有害固相颗粒。本文以硅酸四乙酯、纳米Fe₃O₄为原料,丙烯酸甲酯为接枝单体,制备磁性纳米核,再分别与1, 3-丙二胺、三乙烯四胺进行迈克尔加成反应,成功制备出2种带有磁核和超支化结构的絮凝剂(以1, 3-丙二胺为封端剂(絮凝剂-1),以三乙烯四胺为封端剂(絮凝剂-2)),并通过红外光谱、元素分析的方法测定絮凝剂分子的结构。然后采用絮凝离心的方法,探究2种超支化絮凝剂对废弃油基钻井液的固相含量、密度和粘度的影响。结果表明：絮凝剂加量2.5%时,絮凝剂-1对8#、10#和20#钻井液的有害固相去除率为82.75%、62.30%和70.56%,处理后8#、10#和20#钻井液的固相含量为5.21%、15.34%和14.43%;絮凝剂-2对8#、10#和20#钻井液的有害固相去除率为81.06%、59.13%和69.48%,处理后8#、10#和20#钻井液的固相含量为5.72%、16.63%和14.96%;处理后3种钻井液的密度为0.86~1.16 g.cm^-3;表观粘度和塑性粘度为52~90 mPa·s。其絮凝机理除了电荷中和、吸附架桥作用外,还与其超支化分子结构的吸附性能有关。经过处理的钻井液,满足钻井平台对海上废弃钻井液的要求：8#钻井液(已经过热脱附处理)固相指标5%~7%、10#和20#钻井液(未经处理)固相指标10%~18%,并为其它废弃钻井液的处理提供可借鉴的技术方法。

关键词: 废弃油基钻井液, 絮凝剂, 有害固相, 阳离子多胺类, 超支化结构

CLC Number: 

• TE399

• TE254