Nano-laponite/polymer composite as filtration reducer on water-based drilling fluid and mechanism study

In drilling deep complex formations, most drilling fluid additives have insufficient temperature and salt tolerance, resulting in the decline of drilling fluid performance. This study used 2-acrylamide-2-methylpropane sulfonic acid, acrylamide, dimethyl diallyl ammonium chloride, and modified nano-laponite to synthesize a nanocomposite filtrate reducer (ANDP) with excellent temperature and salt resistance, which can maintain the performance of drilling fluid. The structure of ANDP was analyzed by a transmission electron microscope and an infrared spectrometer. The thermal stability of ANDP was studied by thermogravimetric analysis. The performance of ANDP was evaluated in a water-based drilling fluid. The mechanism was analyzed per clay-particle size distribution, Zeta potential, filter cake permeability, and scanning electron microscopy imaging. The results show that ANDP has good thermal stability and expected molecular structure. The filtration of freshwater drilling fluid after aging at 200°C is 10.4 mL and that of saturated brine drilling fluid is 6.4 mL after aging at 150°C. Mechanism analysis suggests that the ANDP increases the thickness of clay particle hydration layer and maintains the colloidal stability of the drilling fluid. ANDP inhibits the agglomeration of clay particles and significantly reduces the filtration by forming dense mud cake.

在深部复杂地层钻井作业中，多数钻井液添加剂的耐温抗盐性能不足，导致钻井液性能出现衰减。本研究以2-丙烯酰胺-2-甲基丙磺酸、丙烯酰胺、二甲基二烯丙基氯化铵及改性纳米锂皂石为原料，合成了一款耐温抗盐性能优异的纳米复合降滤失剂（ANDP），可有效维持钻井液性能。采用透射电子显微镜与红外光谱仪对ANDP的分子结构进行了表征，通过热重分析法考察了其热稳定性能，并在水基钻井液体系中评价了其应用性能。通过黏土粒径分布、Zeta电位、滤饼渗透率以及扫描电子显微镜成像对其作用机理进行了分析。结果表明，ANDP具备优异的热稳定性能与预期的分子结构。200℃老化后，淡水基钻井液的滤失量为10.4 mL；150℃老化后，饱和盐水基钻井液的滤失量仅为6.4 mL。机理分析结果显示，ANDP可通过增厚黏土颗粒水化层维持钻井液的胶体稳定性，抑制黏土颗粒团聚，并通过形成致密泥饼大幅降低滤失量。