Evaluation of Perforation Flow Performance by Combining 3D-CT Data with CFD Simulation

Abstract The flow performance of perforations in stressed rock simulating reservoir downhole conditions is essential, not only for efficient hydrocarbon recovery, but also for predicting long-term well productivity. Although perforation flow laboratories have been used to shed light on the flow productivity of the perforation tunnels, flow laboratory testing is commonly constricted by the heterogeneous analog core and limited experimental data. Recent advancements in computational techniques have made computational fluid dynamics (CFD) simulation an efficient method to predict the detailed information of the flow and pressure distributions in anisotropic perforated cores. However, traditional CFD studies are commonly based on the ideal shape of the perforation, which could not reflect the real scenario, as the flow performance of perforation is critically affected by the true geometry of the tunnel. In this study, we aim to combine 3D computed tomography (CT) and CFD simulation to describe fluid flow through true reservoir-specific perforations and evaluate their flow performance. Four cores were perforated separately in a laboratory simulating field-well completion under downhole conditions. After scraping the perforations, the cores were imaged using x-ray CT nondestructively. The three-dimensional perforations were subsequently segmented to provide three-dimensional renderings of the perforation tunnels, which were assumed to be open cavities and represented by 3D surface grids. The latter were then embedded in simulation models to represent the physical laboratory setups. The simulation model included the embedded perforated core, casing-cement perforation holes, and radially surrounding proppant, which was a high permeability layer to provide a constant pressure surrounding the core. These models were used to simulate flow through the perforated cores with the consideration of porosity variations, viscous resistance, and inertial resistance of the porous cores and proppant by solving the Reynolds-Averaged Navier-Stokes (RANS) equations with additional porous media model. Three pressure drops (50 psi, 100 psi, and 200 psi) between the inlet and outlet of the cores were investigated for all four tests to identify the effect of pressure drop on flow performance of the perforations. Single-phase flow was simulated, and fluid densities and viscosities were modelled by linear equations related with pressure to mimic the true fluid properties. From the simulation results of the streamlines and velocity vectors distributions, the flow was observed to move upward against gravity due to the higher pressure at the bottom. This resembles the scenario of the flow from the reservoir to the well. Because of the asymmetrical perforations and anisotropic properties of the cores, flow streamlines were skewed and flow through the perforation tunnels was non-uniform for all four perforations. Among them, the fourth perforation provided the most mass flow rate (0.11 kg/s with 200 psi differential pressure), while the third perforation provided the least mass flow rate (0.023 kg/s with 200 psi differential pressure). The CFD simulation with CT-based 3D models provided the details of flow through the perforated cores and quantified the flow performance of different perforation scenarios facilitating the selection of the optimal perforation scenario to maximize the long-term well productivity. In conclusion, this analysis demonstrates how the combination of 3D-CT data with CFD simulation can quantify the flow efficiency of perforations and identify the optimal perforation to maximize well productivity. The methodology can be expanded from single perforation to a well-scale perforation system.