In unconventional reservoirs, production data is generally analyzed using rate transient techniques based on single-phase linear flow models. Such linear flow models use rate-normalized pressure, which is pressure drop divided by reservoir flow rate versus square root of time. In practice, the well fluid production includes water, oil and gas. The oil can be light oil, volatile oil, and gas-condensate as in Bakken, Eagle Ford, and Barnett. Thus, single-phase analysis needs modification to account for production of fluid mixtures.

This paper presents a new approach to analyze multi-phase flow in single and dual-porosity models of unconventional reservoirs. In addition to oil, gas and formation brine, the method accounts for gas condensate production, and the flowback of the injected hydraulic fracturing fluid. Overall, the proposed approach is more comprehensive than the single-phase models but maintains the simplicity of the conventional methods.

The paper includes a workflow and several diagnostic plots for light oils to gas condensates in unconventional reservoirs. Flow rate transient data from two Bakken and Eagle Ford wells will be presented to demonstrate the usefulness of our models. In addition to the mathematical analysis of flow rate and pressure data, we will explain well stimulation configuration and fluid lift methods influence the flow rate history of the Bakken and Eagle Ford wells.

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