Well performance analysis in unconventional reservoirs is a challenging task because of the non-uniqueness associated with estimating well/formation properties. In addition, estimation of reserves is often uncertain due to very long transient flow periods. Recently, new semi-empirical rate-time relations (Ilk et al. 2008 and 2010) have been shown to properly model the rate-time behavior for wells in unconventional reservoirs. The success of these new rate-time relations has led us to focus on finding theoretical and empirical relationships between rate-time model parameters with well/formation properties.
This work attempts to integrate model-based production analysis (i.e., semi-analytical/analytical solutions) and rate-time analysis by using parametric correlations. We perform production analysis and rate-time analysis for various tight gas and shale gas wells, and then correlate the various model parameters from the rate-time equations with the well/formation properties estimated using full (model-based) production data analysis.
We demonstrate the application of the proposed methodology by using a sample of wells producing in tight gas and shale gas reservoirs. We can show that the integration of production analysis and rate-time analysis via parametric correlations is highly-dependent on the size of data sample (i.e., the number of wells) and the data quality. When high-quality data and ample production data are available, formation permeability and fracture half-length are well-correlated with the model parameters of the rate-time relations.