水基恒流变钻井液流型调节剂的制备与性能评价

Evaluation on Preparation and Performance of Rheological Modifier Used in Flat-rheology Water-based Drilling Fluid

流型调节剂是实现水基钻井液恒流变特性的关键处理剂。以丙烯酸(AA)、丙烯酰胺(AM)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)单体为主要原料,采用反相微乳液方法合成了一种流型调节剂,表征了产物的结构、分子形貌、热稳定性等,比较了流型调节剂与传统处理剂对水基钻井液流变性能的影响,结合流型调节剂的分子聚集态结构分析了恒流变机理。结果表明,流型调节剂黏均分子量约7.5×106,平均粒径为258.7 nm,抗温可达260℃。在水基钻井液中,流型调节剂具有良好的流变控制能力,可显著降低温度变化(4数65℃)对关键流变参数的影响。流型调节剂分子的核-壳结构提高了分子刚性和稳定性,其亲水基团在壳层的层级分布可补偿基团损耗,从而维持有效基团数量,确保与黏土片层的缔合作用,维持水基钻井液的稳定性。

Rheological modifier was a key additive to enable flat rheology property for water-based drilling fluids. A specific rheological modifier was synthesized by reverse microemulsion method using acrylic acid （AA） , acrylamide （AM） and 2-acrylamido-2-methyl-propane sulfonic acid （AMPS） as raw materials. The structure, morphology and thermal stability of synthesized product were characterized. Meanwhile, the rheological behavior of rheological modifier and traditional viscosifier in water-based drilling fluid was comparatively investigated. Also, the flat-rheology mechanism of water-based drilling fluid was explored, in combination with the molecular aggregation structure of rheological modifier. The results showed that the average molecular weight of rheological modifier was 7.5 × 10^6, the average particle size was 258.7 nm, and the temperature resistance was high up to 260℃. In water-based drilling fluid, the rheological modifier adjusted the rheological property well, which could dramatically reduce the influence of temperature variation （4--65℃） on rheological parameters. It was concluded that the core-shell structure of rheological modifier should reinforce molecular rigidity and stability. In particular, a layer distribution of hydrophilic radicals around the shell could compensate radical loss caused by harsh environment, and sustain the total quantity of effective radicals. As a result, the association action between polymeric molecular and clay layers could be well maintained, and the flat-rheology of water-based drilling fluid could be realized.