High-Resolution Near-Wellbore Modeling and Its Applications in Formation Testing

Formation Testing (FT) can collect high-resolution data sufficient to capture small variations in fluid and formation properties. Unfortunately, conventional interpretation techniques are rarely capable of processing the data from complex tool configurations and formation properties. Studies have shown that numerical simulation can replicate the complex physics of multiphase fluid flow but often not at the level of detail needed for high-resolution data interpretation. In this paper, we propose a general three-dimensional and multiphase numerical model to incorporate various wellbore and/or tool factors. Unlike the analytical source representation of a well commonly used in reservoir simulation, the proposed model establishes the internal boundary of a well, generally involving the pressure and flow rate at the sandface, where the size of the wellbore or tool configuration is equivalent to or smaller than that of the grid cells. This fully coupled and fully implicit model at a fine spatial and temporal scale is advantageous in revealing further potentially useful information and realizing the synergy across a spectrum of FT applications. As a result, wellbore and/or tool factors, particularly the tool storage effect, can be integrated at a level of detail not previously possible in the absence of a comprehensive wellbore model. The mathematical formulations and numerical schemes are presented. Simulation studies include the primary FT applications in the field, i.e., pressure transient testing and fluid sampling for both oil-based and water-based mud filtrate. These examples show that the proposed near-wellbore high-resolution modeling approach with non-negligible wellbore and/or tool factors permits new insights into fluid flow in FT applications.