Laboratory Testing of Filters and Slot Sizes for Relief Wells

Results of a laboratory experimental program conducted to evaluate three different criteria for the selection of the required screen slot width for gravel pack relief wells are presented. A widely graded filter is used in conjunction with continuous slot screen sections based on the $D_{20}$ size and the $D_{50}$ size of the filter. A third test involves a uniform filter with a continuous slot screen section based on the $D_{10}$ size of the filter. The two filters are compared in terms of (1) Entrance head losses; (2) amount of material entering the screen; and (3) effective radius of the well. The investigation indicates that all three systems result in minimal entrance head losses at the screen. The largest loss of filter material occurs in the well designed with the $D_{50}$ size of the filter. A larger effective well radius is obtained using the widely graded filter. The conclusion applies to conditions shortly after the well is installed and does not consider changes in entrance losses after clogging of well screens and filters that may take place with time.