Balancing Act: Gulf of Mexico Sand Control Completions, Peak Rate Versus Risk of Sand Control Failure
Authors: Wong G. K. , Fair P. S. , Bland K. F. , Sherwood R. S. 
Published: December 2007

This paper outlines a general concept and develops a practical well surveillance method to monitor and operate sand control completions that optimizes production without introducing extra risk of completion impairment and failure. The general concept requires: (a) determining the sand control failure criteria that the surveillance method should be based on, (b) establishing a direct link between the identified failure criteria and pressure transient analysis information, and (c) validating the surveillance method. The proposed surveillance method utilizes readily accessible well information without requiring production log measurements of down-hole velocities within the completion interval.

The proposed method is fully developed for cased hole, gravel pack completions assuming the gravel-filled perforations dominate flow within the completion. The equations are given and velocity criteria are established. In this case the two dominant completion failures are screen erosion and destabilization of annular pack. The maximum flowing velocities for these failure mechanisms can be established using field production logs, laboratory screen erosion data, and mathematical calculations of fluid flow in the annulus pack. The pressure drop across the gravel packed perforation tunnel is the dominant completion pressure drop for the cased-hole gravel pack system. This pressure drop equation is non-linear or proportional to square of perforation flowing velocity.

The well surveillance method monitors down-hole flowing velocity and completion pressure drop to operate the well without introducing unnecessary completion impairment and sand control failure risks. The process of ramping up the well and determining a safe maximum rate goes beyond the strict adherence to absolute values of acceptable completion pressure drop and down-hole velocities and is integrated with prudent surveillance. The method recommends several pressure transient analyses be taken, at increasing flow rate, during the process of ramping up toward the peak rate, to help assess and diagnose the performance of the completion. This integrated assessment by direct measurement of completion pressure drop and corresponding calculation of flowing velocity provides real time feedback of information on the performance of the completion during the ramp up process. Using this direct and simple process, engineers can customize the operating guidelines for each well so that less impaired wells can be produced at higher rates and the more impaired or higher risk wells are identified for remedial operations and produced less aggressively.

This paper demonstrates the application of the proposed concept and surveillance procedure, in reaching the peak rate, for the cased-hole gravel pack completion. Three field examples are provided to illustrate how engineers are able to use standard pressure transient analyses and the proposed simple method to assess the completion response to each additional choke increase and to optimize well productivity during the ramp up process. This paper summarizes key findings on the implementation of this new integrated surveillance tool.