Investigation of drilling fluids containing blast furnace slag for their potential impact on formation damage - A laboratory study

This work discusses the effect of incorporating blast furnace slag (BFS) as an additive in water-based drilling fluids. The intent of this treatment i s rapid development of a thin, impervious, and easily removable filter cake , thereby minimizing detrimental impact of the drilling fluid on formation productivity as opposed to previous applications of BFS in universal fluids . To evaluate the impact of BFS on filter cake properties, permeability plu gging apparatus (PPA) tests and dynamic formation damage (DFD) studies were conducted. Drill-in fluids and dispersed muds were tested using varying qu antities of BFS. Once a steady rate of dynamic filter cake deposition was a chieved, the BFS in the filter cakes was chemically activated. The results obtained from these activation studies were compared with those obtained wi th no BFS and with unactivated BFS. The nature of the filter cakes was exam ined with an environmental scanning electron microscope (ESEM). Results obt ained from the PPA tests indicate substantial decreases in initial spurt lo ss and filtrate volume with increasing concentration of BFS, The DFD studie s substantiate the aforementioned observations and show enhancement of retu rn permeabilities with BFS activation. ESEM studies demonstrate that BFS ca n consolidate filter cakes.