A sand control device using prepacked metallic wool designed for total exclusion of sand in thermal operations was tested in Lloydminster and Athabasca unconsolidated sand formations. The results obtained from 20 different applications, which are summarized in this paper, indicate that sand production previously plaguing some locations disappeared after the new filter was introduced. However, high pressure drops and reduction in production rate were sometimes associated with partial plugging of the filter in fine grained formations.

As a result of the field observations, a laboratory investigation was undertaken to design new criteria for the prepacked metallic wool filter and to achieve better control of solids by using a partial filtration strategy. The experimental program presented in the paper includes a laboratory testing method which replicates open-hole completions. Alteration of filter permeability, including the formation of a filter cake in open-hole conditions, indicates that a different sand control strategy should be designed for set-through and open-hole completions. A filtration model based on laboratory experiments using a prepacked metallic wool filter for sand control in an open hole is suggested. The model assesses the risk of plugging as a function of formation median grain size, filter compression, and the grade of metallic fibers. The model provides practical criteria for designing a prepacked metallic wool filter for partial exclusion of sand and to avoid a rapid loss of filter permeability in fine-grained, unconsolidated formations.

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