Description: A general wellbore flow model is presented to incorporate not only frictional, accelerational and gravitational pressure drops, but also the pressure drop caused by inflow. Influence of inflow or outflow on the wellbore pressure drop is analyzed. New friction factor correlations accounting for both inflow and outflow are also developed. The greatest source of uncertainty is reservoir description and how it is used in simulators. Integration of data through geostatistical techniques leads to multiple descriptions that all honor available data. The reality is never known. The only way to reduce this uncertainty is to use more data from geological studies, formation evaluation, high resolution seismic, well tests and production history to constrain stochastic images. Even with a perfect knowledge about reservoir geology, current models cannot do routine simulations at a fine enough scale. Furthermore, we normally don't know what scale is fine enough. Upscaling introduces errors and masks some of the physical phenomenon that we are trying to model. The scale at which upscaling is robust is not known and it is probably smaller in most cases than the scale actually used for predicting performance. Uncertainties in the well index can cause errors in predictions that are of the same magnitude as those caused by reservoir heterogeneities. Simplified semi-analytical models for cresting behavior and productivity predictions can be very misleading.
Date: April 29, 1997
Creator: Aziz, Khalid; Arababi, Sepehr & Hewett, Thomas A.
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Partner: UNT Libraries Government Documents Department