有利于改进水包油钻井液性能的固体乳化剂的研制及应用

在水基泥浆中加入5—12%矿物油(或柴油)所形成的水包油钻井液已在胜利油田广泛应用于防止卡钻的发生。但在某些情况下,这种泥浆体系的乳化稳定性不能满足钻井作业的需要。为了克服这一缺点,研制出一种颗粒极细并具有特殊润湿性(弱亲水)的固体乳化剂,并已成功地应用于改进乳状液的稳定性和钻井液的其它性能。 在提出该项技术之前,对各种不溶于水的微细固体颗粒对水包油乳状液稳定性的影响进行了较深入的研究。这些颗粒状物质包括膨润土、有机土、高岭石粉、重晶石粉、两种颗粒尺寸不同的碳酸钙粉、两种具有不同润湿性的硅石粉以及新研制的固体乳化剂。为评价这些微粒对乳化稳定性的贡献,分别开展了乳状液稳定性实验和液滴聚并实验。使用静置12h后乳状液的体积和油/水滴的半衰期作为乳状液稳定性的评价指标。实验结果显示,对于给定的油/水体系,乳状液类型和稳定性取决于固体颗粒的类型、尺寸、浓度和润湿性,以及是否有表面活性剂存在。与其它类型的颗粒相比,固体乳化剂的微粒可为水包油乳状液提供最有效的稳定性。同时实验中发现,在某些情况下,固体乳化剂微粒还能有效地稳定油包水乳状液,因为其润湿性接近于中性。 目前,使用新研制的固体乳化剂稳定的水包油乳化泥浆已经成为胜利油田钻定向井和水平

Development and Applications of the Solid Emulsifier Used to Improve the Performance of Oil-in-water Drilling Fluids

The oil-in-water emulsion drilling fluids, prepared by adding 5-12% (by volume) of mineral oil (or diesel) to water-based muds, have been widely used for stuck-pipe prevention in the Shengli Oilfield. In some cases, the emulsion stability of this kind of mud system is not strong enough to meet the requirements of drilling operations. To overcome this drawback, a solid emulsifer, which is characterized by its very small particle size and special wetting behavior (slightly water-wet), has been developed and successfully applied to improve the emulsion stability and other performances of these drilling fluids. Prior to the development of this technology, an extensive study was conducted to deal with the influence of various kinds of finely divided insoluble solid particles on oil/water emulsification. The substances used include bentonite, organophilic clay, kaolinite, barite, two kinds of calcium carbonate with different particle sizes, two kinds of silica with different wetting behaviors, and a newly developed solid emulsifier. Both the emulsion stability experiments and the drop coalescence experiments are performed to evaluate the contribution of these particles to emulsification. The measured final emulsion volume disappears after 12 hours and the half-life for water and oil drops are used as the measures of emulsion stability. The experimental data show that the type, size, concentration and wettability of the particles, and the presence of some surfactants control the type and stability of emulsions for a given oil/water system, and the fine particles of the solids emulsifier provide the most effective stabilization for water-continuous emulsions compared with other kinds of particles. Meanwhile, it can be observed that these particles also stabilize oil-continuous emulsions effectively in some cases since their wetting behavior is close to neutral. The O/W emulsion mud stabilized by the newly developed solid emulsifier has become one of the major mud systems used in directional and horizontal well drilling in the Shengli Oilfield. In addition to the improvement of emulsion stability, this solid emulsifier has the advantages of improving the lubricity of mud cake and is beneficial to the control of rheological properties and filtration.