Abstract
There are two considerations related to the drilling mud when installing sand screens: plugging of the filter media when running the screens into the wellbore, and then transporting the filtercake back through the screen when the well is produced. For compliantly expanded sand screens producing the mud filtercake is potentially more problematic as the screen is pressed into the cake during installation, and there is no annulus to allow the cake to break up and disperse before reaching the screen.
This paper describes laboratory tests for evaluating drilling fluids for use in the reservoir section when expandable sand screens are to be installed. Several examples of the results of the laboratory tests are related to well performance in the field to establish the relevance of test results. Only partial removal of the mudcake is required to give good return permeability in laboratory tests, and so field performance is predicted from comparing results with and without the screen filter medium present. This method correlates to the field, where low skins and good production have been observed with muds which give similar return permeabilities independent of screen presence in laboratory tests. Furthermore, forcing the screen into the mud filtercake during installation does not generally impede filtercake removal.
Based on these results some limitations on drilling mud formulation and conditioning for successful screen applications are established. The effect of screen presence on chemical clean-up treatments is briefly discussed, and an example is given where a failure in the field was related to poor mud conditioning prior to running the screen.
