Successful Application of Unique Polyamine High Performance WaterBased Drilling Fluid in Bohai Bay Shale Formations

Abstract With the increasing demand of oil and gas resources, the drilled formations are becoming more and more complicated. Nevertheless, in the process of developing these hydrocarbon resources, wellbore instability caused by active shale hydration and dispersion is always a great challenge around the world. Therefore, it is necessary to develop a high performance water-based drilling fluid reaching into the property realm of oil-based drilling fluid but also environmentally acceptable. This paper detailed the inhibitive properties of a novel polyamine shale hydration inhibitor SDJA-1 through bentonite inhibition test, cuttings hot-rolling dispersion test, bulk hardness test and X-ray diffraction analysis. The results show that polyamine is highly inhibitive and high temperature resistant, superior to conventional shale inhibitors. Incorporated with shale encapsulator and lubricator, a polyamine high performance water-based drilling fluid was established based on triple inhibition. Extensive laboratory work was carried out to compare the properties of the system with other conventional inhibitive water-based drilling fluids and oil-based fluid. The results indicate that the system is highly inhibitive, rheology stable and excellently lubricant, approaching to the general oil-based drilling fluid. Drilling in Bohai bay presents some unique challenges primarily related to wellbore instability in drilling through the highly complicated and reactive shale formations. Therefore the uniquely engineered polyamine high performance water-based drilling fluid was proposed with a special emphasis on wellbore stability. Three wells trials demonstrate that the system impart excellent performance like shale stability, trouble-free trips, and rheology stability. No bit balling is observed and ROP is improved compared to before. In conclusion, the system shows outstanding performance in all aspects and contributes to a high degree of success.