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Proppants—What 30 Years of Study Have Taught Us


 The earliest hydraulic-fracture stimulations used poorly sorted river sand as the proppant. Since this first experiment with proppants, the industry has evolved to offer a broad range of proppant choices although, by far, natural sand of some type remains the proppant of choice for a variety of reasons. For the past 30 years, an industry Consortium has engaged in a continuous program of building knowledge and understanding in the behavior of all types of proppants used in hydraulic fracturing.
 There are many basic understandings about the behavior of proppant packs under downhole reservoir conditions that have been developed through thousands of tests that have been performed through this work. These include the effects of proppant type, grain failure, fines migration, embedment, non-Darcy and multiphase flow, cycling, loading, packing arrangement, fracture-fluid damage, and others. All these effects can be at work simultaneously to negatively affect flow in the propped fracture, and the recognition of these effects assists in explaining observed well performance.
 This paper will present current knowledge of proppant performance that is sometimes misunderstood or wrongly applied and will assist the practicing engineer in well diagnostics and stimulation design.