CFD Modeling of Annular Flow Improves Velocity Guideline for Maximum Production Rates of Stand Alone Screen Completions

Abstract Stand-alone completions using erosion resistant screens is an attractive solution, so long as the maximum fluid velocity that can be handled by the screen is well known, and that a comprehensive annular flow model is developed to identify hot spotting risks along the wellbore. In an ideal world the full geometry of the reservoir, the well and completion could be modelled in a single continuous fluid model. But the reality is somewhat completion and hardware/time dependent: simple barefoot open hole or cased and perforated completions can be fully captured, but fully capturing the geometry of complex mesh sand screens for the entire well length is currently not possible. The degree of compromise in the geometry depends on the complexity of the completion, the well length, and the hardware (computing power) available. Even with significant computing power, only very short sections of screen can be included in the full well model, and depending on the well length including every base pipe hole in a long well may be challenging. The problem is compounded when dealing with mesh screens and the complexity of its woven structure. The CFD model developed to estimate annular flow velocity requires three steps to assess fluid velocity passing through and approaching the screen filter media. Step 1 – A full well model including the reservoir is developed, with base pipe open area included and screen represented by "porous media". This step identifies the highest risk parts of completion for detailed modelling in step 2.Step 2 – The full well model zooms on areas of higher velocity/risk with full base pipe hole geometry modelled for the shorter sections of interest.Step 3 – Small coupon sized to represent sections of screen are modelled with fluid rate input derived from step 2 for maximum velocity location thought the screen wires and approaching the screen. Considerable validation has been performed over a range of fluids, rates and well geometries to confirm that the process is rigorous and enables true velocities for different screen types to be compared through screen velocities. This full wellbore digital model was used to estimate annular velocity and compare it with sand pick up rates to assess the risk of screen plugging. It was also combined with a laboratory calibrated erosion model to determine ultimately safe production rates for different screen designs Based on this lab-supported CFD approach, refined guidelines are proposed. Several screen designs are compared and improvement in maximum velocity recommendations is established for the first time for premium mesh screens. The methodology proposed may be used to provide actionable production guidance based on suspended solids loadings and production rates.