Contamination of High Density Drilling Fluid at High temperature and Handling thereof in Northeast Sichuan

The construction drilling fluid density in the Puguang Maoba block, Tongnanba Ma 3 block, Yuanba block in Northeast Sichuan is high. During the cleaning and plugging period , the high-density drilling fluid is common to experience high temperature thickening and consolidation after being contaminated by cementing cement.Due to unclear pollution mechanisms and lack of effective treatment methods, a high proportion of replacement mud is usually required, resulting in long treatment cycles and high costs. This article briefly analyzes and verifies the pollution mechanism of cementing cement on high-temperature and high-density drilling fluid through simulation experiments. The results show that the main reasons for pollution are: firstly, the high pH value of the drilling fluid after pollution leads to high-temperature thickening; secondly, some additives in the cement slurry invade the mud and solidify at high temperature, adsorbing a large amount of free water and causing thickening of the mud.In response to the pollution mechanism, AOP-1, a polymeric aluminum anti collapse agent, was selected as an efficient high-density water-based drilling fluid cement pollution treatment agent, which was successfully applied in four wells. The on-site application shows that AOP-1 has a good treatment effect on high-temperature and high-density water-based drilling fluid well cementing pollution, which avoid a large amount of displacement of drilling fluid after pollution and improving treatment efficiency.