The improvement of mud displacement from the annular space of the borehole in terms of the selection of washing fluids and pre-flushes

One of the most important steps in drilling a well is cementing the annular space between the casing and the rock formation. This process is significant because of the stabilization of the well and effectively separation of the consecutive rock horizons. It is essential that cementing ensures the durable and effective insulation of the rock mass. The complete displacement of the drilling fluid from the annular space is particularly important due to a number of negative phenomena related to its insufficient extrusion. The cement slurry pressed through the annular space displaces the mud but is unable to thoroughly remove the residue left behind sufficiently. The subject of the laboratory research was to check how selected washer affect the efficiency of displacing drilling fluid from the annular space of the borehole. In addition, the tests included the determination of the optimal washing time and optimal pumping rate of the washing fluid.