The Method Research Of Well-bore Stability Evaluation In Shale By Logging

Well-bore instability related with shale mostly is a serious and worldwide technical problem during the process of drilling. The thesis mainly researched the coupling effect of mechanics and chemistry on the well-bore stability of shale, also the logging evaluating methods.Firstly, the influence of well-bore stress and rock properties by the physical-chemical effect between shale and drilling fluid was analyzed; By making full use of the advantages of logging including great information , well continuity and high reliability etc, the logging methods of the parameters about shale hydration including clay minerals in shale, cation exchange capacity(CEC) and so on was studied; The chemical-mechanical coupling effect of well-bore stability was studied and the evaluation model of logging was built, and the safe density window of drilling fluid was predicted reasonably. Furthermore, the logging evaluation software of chemical-mechanical coupling effect of well-bore stability was developed, which could provide the safe density window and the analyzing profiles for the hydration characteristic indexs in shale etc. The practical logging data aiming at the second district of Cheng Hai in DaGang Oilfield was proceeded and primarily analyzed.