How do you troubleshoot well test anomalies?

1 Check the test objectives

The first step to troubleshoot well test anomalies is to review the test objectives and the assumptions that were made to design and execute the test. For example, you may have assumed a constant bottomhole pressure, a homogeneous reservoir, or a single-phase flow. If these assumptions are violated by the actual well and reservoir conditions, the test results may not reflect the true well behavior. Therefore, you should check if the test objectives are still valid and relevant, and if the test duration, frequency, and type are appropriate for the well and reservoir characteristics.

2 Verify the data quality

The next step is to verify the quality of the data that was collected during the well test. Data quality can be affected by various factors, such as measurement errors, instrument malfunctions, noise, outliers, or missing values. You should inspect the data for any signs of inconsistency, irregularity, or deviation from the expected trends. You can also use statistical methods, such as correlation analysis, regression analysis, or error analysis, to assess the accuracy and reliability of the data. If you find any data quality issues, you should try to correct them or discard them before proceeding to the interpretation stage.

3 Analyze the well behavior

The third step is to analyze the well behavior and compare it with the theoretical models and predictions. You can use different methods, such as pressure transient analysis, decline curve analysis, or rate transient analysis, to evaluate the well performance and estimate the reservoir parameters. You should also plot the data on various graphs, such as log-log plots, semi-log plots, or Cartesian plots, to identify the flow regimes and the boundary effects. If you observe any discrepancies or anomalies between the actual well behavior and the expected well behavior, you should investigate the possible reasons and implications.

4 Identify the anomaly sources

The fourth step is to identify the sources of the anomalies and classify them into two categories: physical and non-physical. Physical sources are related to the actual well and reservoir conditions, such as multiphase flow, heterogeneity, anisotropy, fractures, faults, interference, or skin. Non-physical sources are related to the test design, equipment, data acquisition, or interpretation, such as wellbore storage, superposition, wellbore phase redistribution, pressure gauge drift, or model misfit. You should use your knowledge and experience, as well as the available literature and data, to determine the most likely sources of the anomalies and their effects on the test results.

5 Apply the corrective actions

The final step is to apply the corrective actions that are appropriate for the identified sources of the anomalies. Depending on the nature and severity of the anomalies, you may need to modify the test design, adjust the equipment settings, correct the data, or change the interpretation method. For example, you may need to extend the test duration, change the flow rate, recalibrate the instruments, filter the noise, or use a different model or solution technique. You should also document the anomalies and the corrective actions, and validate the results with other methods or data sources.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?