The Synthesis and Application of a New Plugging Inhibitor PAS-5 in Water-Based Drilling Fluid

Wellbore instability caused by the dispersion of the clay is one of the most important challenges in drilling operation of fractured formations. The synthesis of new plugging inhibitors and the research of drilling fluid systems are key steps to keep the wellbore stabilization. In this paper, the limitations of conventional drilling fluid inhibitors are discussed and a new plugging inhibitor PAS-5 is synthesized by using amine inhibitor, polyethylene glycol and asbestos fiber as the main monomers. The detailed synthesis step of the plugging inhibitor PAS-5 is illustrated and its action mechanism is explained by scanning electron microscopy. In order to express the good effect of the PAS-5, a new evaluation system is used to indicate its plugging performance. At the same time, the plugging inhibitor PAS-5 was used on-site drilling operation in the Ordos Basin. The results of research show that the synthesis process of PAS-5 is simple and the effect of plugging inhibition is obvious. Compared with conventional treatment agents? PAS-5 outperforms sulfonated asphalt FT-1 and emulsified asphalt RHJ-3 in terms of plugging inhibition performance, with a plugging rate of 90.5% and roller recovery rate of 93.7%. It also has better temperature resistance, there is almost no change in viscosity and filtrate loss when the temperature rises from room temperature to 80°C. The field application results indicated that PAS-5 meets the requirements of drilling, that the reaming time of the trips of the wells is shortened considerably, that the ROP is improved, and that the hole enlargement rate is less than 6%. During the drilling process, PAS-5 can inhibit formation hydration and seal small cracks, thus maintaining the stability of the borehole. This study synthesized a novel plugging inhibitor PAS-5 and an evaluation system was adopted to reveal its plugging performance, and achieved good application effect in on-site drilling operations.