摘要：It is the key and difficult point in the development of shale gas formation to achieve wellbore stability, and safe and efficient drilling in horizontal well drilling. At present, oil-based drilling fluid is mainly used in the horizontal well drilling of shale gas, but its poor environmental performance and high cost makes it not suitable for the development trend of oil industry. Therefore, the research and promotion of new water-based drilling fluid is imperative. In this study, the geological characteristics of shale gas reservoir was analyzed by means of XRD and scanning electron microscope. The mechanism of wellbore instability in this area was analyzed, and the technical difficulties and solutions of horizontal well drilling fluid were also put forward. At the same time, the relevant tests were carried out to evaluate the key performance of the water-based drilling fluid, such as plugging, inhibition and environmental protection, under the conditions of high temperature and pressure. The experimental results revealed that the plugging performance of the new water-based drilling fluid system was better than that of polymer drilling fluid, and closed to that of oil-based drilling fluid, which can significantly reduce the decline in shale strength. The secondary recovery rate of the system was 92.37%. Meanwhile, the value of EC50 was 11,000mg/L, which is non-toxic. The system has good plugging and inhibition ability, and is close to the effect of oil-based drilling fluid. Furthermore, it can not only save drilling costs, but also greatly reduce environmental pressure, and has a broad application prospect.
