Conventional High Rate Well Completions: Limitations of Frac&Pack, High Rate Water Pack and Open Hole Gravel Pack Completions

Abstract New Deep Water completions in the Gulf of Mexico (GOM) are expected to produce over 20,000 bpd or more than 100 MMscf/d from reservoirs less than 200 ft thick. At these high flow rates (100 bpd/ft, 500 Mscf/d/ft) turbulence in the gravel filled perforations starts to play a significant role. This study attempts to assess which type of completion is most suited for these high rate wells. Frac&Pack (F&P) completions are compared with High Rate Water Packs (HRWP) and Open Hole Gravel Packs (OHGP). Both Oil wells and Gas wells are analyzed. The concept that, in cased hole gravel packed completions, the main source of damage is in the perforation tunnels (casing and cement sheath) has been used to build inflow models for each completion type. These models use standard inflow equations for radial flow in the reservoir and linear flow in the perforation tunnel. This inflow model was matched to field data for HRWP and F&P completions by changing the effective number of perforations flowing as well as the average gravel permeability in these perforations. For OHGP completions no detailed field data was available and general completion assumptions were used as inputs to estimate the inflow performance. Results generated from these field calibrated models, in the predictive mode, show that for high rate gas wells (> 500 Mscf/d per ft of perforations), where the high pressure drops in the perforation tunnel dominates the inflow, the benefits of fracturing the formation diminishes for reservoirs with permeabilities greater than 150 mD. Above 150 mD. a HRWP become more efficient than a F&P. At reservoir permeabilities above 600 mD OHGP's however may become more efficient. In high rate oil wells (> 100 bpd/ft perfs) the total pressure drop is not so much dominated by the perforation tunnel. Hence the benefits of fracturing the formation continue to a permeability of 900 mD before OHGP becomes more efficient. The field matches suggest that F&P completions in general only have 0.7 to 2.3 shots per foot (spf) flowing with an average gravel permeability of no more than 17 Darcy. For HRWP it is found that more perforations are flowing (5 spf) and that the average gravel permeability is still high (13.6 Darcy).