Flowback Production Optimization for Choke Size Management Strategies in Unconventional Wells

Abstract

The flowback period of the unconventional wells is very critical as it can cause determential ecomonical effects if not properly optimized. The success of the well is as dependent of the completion program as it is from the flowback program applied during the initial production period of the well. If ineffective operations are performed on the flowback phase {independently on the completion technology}, the well can underperform and become unsuitable for development. In unconventional wells, it is necessary to develop the safe well operating envelope in safe zone to prevent the early proppant flowback based on the reservoir parameters and the completions in place. The well can start producing in this developed safe well operating envelope by controlling the wellhead pressure and surface valves and optimizing the proper choke size to keep the well with free proppant production. Proppant flowback production modeling captured decline of water production as well as the increase of liquid production when a selected choke sizes is applied. By controlling the flowing bottomhole pressure (FBHP) during defined flowback period, the volume of proppant production decreased with decreasing chokes sizes and increasing long flowback periods. This study showed that the optimized choke sizes to improve the longer production periods depended on the sensitivity of pressure drawdown, liquid rates, wellhead pressure, and fracture geometry parameters. Numerical results showed that the critical parameters affecting the stability of the proppant pack are fracture closure pressure, reservoir pressure, proppant type and size, and type of fracturing fluid. Proppant flowback program developed by using optimized choke size, wellhead pressure (WHP) and FBHP, and amount of producible proppant volume predicted for designed flowback production periods. At the beginning of the flowback period, the wellbore is filled with fracturing fluid and the minimum choke size should be used as small as possible (12/64"). The controlled FBHP management over 45 days of flowback period corresponds to an average drawdown rate of 10 psi/day to 200 psi/day. Finally, the developed workflow applied to design flowback periods and selection of choke sizes to prevent excessive proppant production and proppant crushing in hydraulically fractured unconventional wells. This paper presents the methodology and workflow for selecting the required choke sizes and flowback periods to minimize the risk of production of high volume proppant during the flowback period after fracturing. The case study presented here in will present the benefits of optimizing choke sizes and flowback programs for reducing the damage to fracture conductivity and to increase the cumulative production. The optimized choke sizes, flowback strategies and workflow established with this case study have proven to increase the performance of fractured unconventional wells.

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