Research on the effect of drilling fluid’s pH value on the coal’s wettability

摘要

Drilling fluid contacts with the surface of coal and fractures fully during the drilling process for CBM, its pH value has direct impact on the wettability of coal, affecting the seepage of CBM further. Therefore, the research about the effect of drilling fluid’s pH value on the coal’s wettability has important practical significance. The influence law of drilling fluid’s pH value on the coal’s wettability was studied through lots of experiments, the results showed that the wettability was related to the pH value of drilling fluid, decreases firstly, increases secondly and decreases at last, the coal’s hydrophilicity was the weakest at the pH value of 9, and the hydrophilicity of coal was weaken further after the addition of surfactants. The conclusions provide strong technical guidance for selecting drilling fluid and optimizing fluid performance, and it helps to protect the reservoir and increase CBM production.