Accurate forecasts of future production and the associated economics for conventional wells are possible with Arps decline curves as these wells attain boundary-dominated flow (BDF) relatively quickly. Unconventional wells completed in low permeability formations can require several years (and several annual evaluations) to reach boundary-dominated flow, often making Arps based production forecasts for these wells unreliable. Application of methods based on production history, such as rate-transient analysis (RTA), may provide reasonable production forecasts but require wellhead or bottomhole pressures in addition to production rates. In contrast, data available for estimation of proved reserves for unconventional wells routinely includes only rate data from transient flow, limiting the utility of both the Arps and most RTA methods. This study addresses the ability of three models which require only production data, the modified Arps, Duong, and stretched exponential decline model (SEDM) methods, to fill this gap by using time-slice data (6 months, 1 year, 3 years) from long-lived unconventional wells. Accuracy of these models in predicting future well performance and the resulting economics based on constant prices and constant operating expenses, and the ability of these reserves estimates to meet the SEC requirement that proved reserves should remain constant or increase over time are considered.

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