水基钻井液强吸附多元醇酯键合润滑剂及作用机理

Study on Mechanisms of a Highly Adsorptive Polyol Ester Bonded Lubricant for Water Based Drilling Fluids

常用水基钻井液润滑剂在金属摩擦界面上的吸附力弱,难以形成致密、且耐剪切的润滑膜,导致钻井摩阻、扭矩高,引发阻卡、卡钻等井下事故。为提高润滑剂在金属钻具表面的吸附能力,以多元醇和长链脂肪酸为原料,通过脱水缩合制备了一种多元醇酯键合润滑剂,其极压摩擦、滤饼黏附及“点对点”摩擦的润滑性能均优于国内外同类产品,抗温达150℃;通过四球摩擦实验、扫描电镜观察、X射线光电子能谱等研究了键合润滑剂的作用机理,表明其多羟基结构可与Fe元素形成强于普通物理吸附的键合吸附,从而可在金属钻具表面形成厚度约45 nm的致密、抗剪切润滑膜;同时也可吸附在重晶石表面,利于降低钻井液内摩擦。

Common lubricants used in water based drilling fluids have weak adsorption on the friction interfaces of metals, and therefore are difficult to form dense and shear-resistant lubricating films thereon, which leads to high friction and torque during drilling. High friction and torque generally result in pipe sticking and high overpull or resistance during tripping of drill string. To improve the adsorption of drilling fluid lubricants on the surfaces of drilling tools, a polyol ester bonded lubricant was developed with a polyol and a long-chain fatty acid through dehydration condensation reaction. This new lubricant worked better in extreme pressure friction test, filter cake adhesion test and “point-to-point” friction test than similar products both from China and abroad. It can be used at temperatures up to 150 ℃. The working mechanisms of the lubricant were studied through four-ball friction test,SEM observation and X-ray photoelectron spectroscopy etc. It was concluded that the polyhydroxy structure of the lubricant can form bonded adsorption on the surface of Fe, which is stronger than the general physical adsorption, it thus can form a dense and shear-resistant lubricating film, having a thickness of about 45 nm, on the surfaces of drilling tools. The lubricant can also be adsorbed onto the surfaces of barite particles, thereby reducing the internal friction of a drilling fluid.