Water coning in permeable faults
Research output: Thesis › Master's Thesis › Research
The main objective of this thesis is to provide insight into the water coning behavior of wells drilled into permeable geological faults in clastic as well as in naturally fractured basement reservoirs. In both cases a vertical fault with large lateral and vertical extent is considered as a flow zone for oil and water and is produced by a horizontal well placed at the center of the domain. If a certain maximum water-free production rate is exceeded, an early inflow of water into the well can be expected, referred to as water coning. This thesis provides an analytical solution for this maximum water-free production rate which is afterwards used to verify 2D simulations in clastic and naturally fractured reservoirs. All the simulations are run with the commercial CFD software ANSYS Fluent. Additionally, the influence of inertia, boundary effects and different fault parameters on the pressure drop is discussed. The analytical solution for the maximum water-free production rate in case of laminar flow in a fault with specified permeability, as expected in sandstone reservoirs, results in a value of 2.59•10-6 m3/s. In comparison, the numerical solution yields a higher value of 1.13•10-5 m3/s resulting in a relative error of 0.8. Using the assumption of a permeability based on the parallel-plate model and Forchheimer dominated flow for an idealized case of a conduit in a naturally fractured reservoir, a maximum water-free production rate of 5.36•10-4 m3/s is determined analytically. By changing the production rate in different simulation scenarios, the numerical solution indicates a rate of 8.48•10-5 m3/s. In this scenario turbulent flow behavior is monitored and a relative error of 3.3 observed.