| http://www.w3.org/ns/prov#value | - In the production of wells, such as oil and gas wells, that extend into or through sandy, or unconsolidated earth formations, it has been a practice to place a so-called well liner or screen in the well bore and to fill the annulus with gravel which prevents the sand or unconsolidated earth from flowing into the well bore and filling it or being carried to the top of the well in the production flu
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