Forecast of Sand Deposition at Low Points of a Riser - Jubilee Field Case Study

Abstract

Abstract The Jubilee Field is located at about 60 km offshore Tano Basin, Ghana. It produces from an average water depth of about 1100 m through subsea components such as manifolds, flowlines and flexible risers into a Floating Production, Storage and Offloading (FPSO) platform at surface. The paper examined the flow dynamics and sand deposition pattern in the east loop riser of the Jubilee Field under a given operating conditions. It employed computational fluid dynamics technique aimed at forecasting the possible deposition areas of sand in the riser. Eulerian discrete phase model was adopted in predicting sand flow pattern at areas encompassing the low points of the riser. It was observed that for the given flow conditions, there is the possibility of sand deposition and/or accumulation in some sections of the riser. The study predicted the possibility of sand deposition within the vicinity of 14 m from the riser base, and also at sections from the touchdown point up to 2 m downstream of that point. It established that low points in riser bathymetry are possible sources for onset of sand deposition. Sand dispersion decreases from the point of injection towards the lower region of the flow domain downstream from the injection point. The study would aid in proposing effective riser bathymetry to mitigating the impacts of sand deposition in a riser. It will contribute significantly in developing an effective sand management strategy. Introduction The Jubilee Field is a 'green' field located approximately 60km offshore Tano Basin of Ghana with an estimated recoverable reserves of over 370 million barrels and an upside potential of about 1.8 billion barrels. Cased Hole Frac Pack (CHFP) completions were performed on the Jubilee wells; as a long term insurance to mitigate sand production although studies showed the reservoir was generally competent and consolidated.