Prediction of gas well deliverability is important for reservoir management. Conventional flow after flow, isochronal or modified isochronal tests are common methods for calculation of well deliverability. Single-point test using Vogel-type dimensionless inflow performance relationships (IPR) was also proposed to overcome the need for multi-point tests. However, analysis of field data showed that existing dimensionless IPR correlations fail to accurately predict well deliverability for some reservoir conditions. In this study, a wide range of reservoir rock and fluid data was used to develop a comprehensive dimensionless IPR correlation for calculation of gas well deliverability from single-point test data. Multi-point well test data from 61 different gas wells of 15 fields were used to compare predicted absolute open flow (AOF) and calculated AOF from multi-point test data. The data used for validation of the proposed dimensionless IPR cover a wide range of actual AOFs (2.1–1411 MMSCF/D). Good agreement between predicted well deliverability from new dimensionless IPR and that from multi-point test was achieved. In addition, superiority of the new dimensionless IPR to previous correlations was confirmed for a wide range of reservoir conditions through error analysis. The average absolute error for new model is 11.6% (standard deviation of 8.5%) while for the other models are 85.9% (standard deviation of 148.1%) and 68.6% (standard deviation of 115.3%) for a wide range of field data.
Usually four-point backpressure test, an isochronal test or a modified isochronal test is conducted to predict gas well deliverability. During past decades several simple dimensionless inflow performance relationships (IPRs) have been developed to eliminate the need for conducting multi-point test by using only data from a single drawdown or build-up test. The capability and accuracy of these models should be evaluated with measured field data using wide range of fluid and rock properties. This paper addresses the limitations, accuracy and optimal use of proposed dimensionless inflow performance correlations (Mishra and Caudle, 1984, Al-Attar and Al-Zuhair, 2009) based on back-pressure field test data of 53 wells that cover a broad range of AOF, reservoir pressure, well stabilized rate and pressure. The results show that both methods lose their accuracy at high rate and low drawdown conditions with unacceptable overprediction of AOFs. None of the studied models are recommended to use when dimensionless pressure (ratio of the well pressure to the reservoir pressure) is above 0.9. Advantages and ranges of optimal use of different models are discussed through error analysis.
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