Estimation of completion pressure losses in gravelpacked and frac-packed wells is generally performed through use of empirical or semi-empirical analytical relations. This paper reports on work conducted by Conoco to compare numerical simulation results with analytical inflow performance relations. The work shows how and where completion pressure losses occur in flow to gravelpacked and frac-packed wells.
A fine gridded finite difference model has been developed to simulate flow and pressure loss behavior in the reservoir/well system. The grid system employs elements as small as 1 cm5 to model complex near well and intra-well flow effects including near-wellbore flow convergence to perforations, flow distribution between perforations and flow through gravel-filled perforations. These near-wellbore effects are reviewed for both symmetrical gravelpacked well flow cases and asymmetrical flow cases associated with frac-packed wells. Intra-well flow through gravel-filled perforation tunnels and the casing/screen annulus is also modelled for both cases.
Pressure losses and skin effects due to damage, fracturing and wellbore geometry are calculated through the flow system and compared to predictions from analytical relations. Results of these comparisons lead to an improved understanding of the effects of damage and flow asymmetry on gravelpacked and frac-packed well performance. Further, they show how current analytical skin relations can be enhanced to provide more effective completion pressure loss predictions.