There are two considerations related to the drilling mud wheninstalling sand screens: plugging of the filter media whenrunning the screens into the wellbore, and then transportingthe filtercake back through the screen when the well isproduced. For compliantly expanded sand screens producingthe mud filtercake is potentially more problematic as thescreen is pressed into the cake during installation, and there isno annulus to allow the cake to break up and disperse beforereaching the screen.This paper describes laboratory tests for evaluating drillingfluids for use in the reservoir section when expandable sandscreens are to be installed. Several examples of the results ofthe laboratory tests are related to well performance in the fieldto establish the relevance of test results. Only partial removalof the mudcake is required to give good return permeability inlaboratory tests, and so field performance is predicted fromcomparing results with and without the screen filter mediumpresent. This method correlates to the field, where low skinsand good production have been observed with muds whichgive similar return permeabilities independent of screenpresence in laboratory tests. Furthermore, forcing the screeninto the mud filtercake during installation does not generallyimpede filtercake removal.Based on these results some limitations on drilling mudformulation and conditioning for successful screenapplications are established. The effect of screen presence onchemical clean-up treatments is briefly discussed, and anexample is given where a failure in the field was related topoor mud conditioning prior to running the screen.
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