Magnolia Deepwater Experience—Frac Packing Long, Perforated Intervals in Unconsolidated Silt Reservoirs

Abstract

Summary ConocoPhillips is developing the Magnolia field with a tension-leg platform (TLP) in 4,674 ft of water at Garden Banks Block 783 in the Gulf of Mexico. The wells target multiple zones, resulting in complex directional wells with 50–60 maximum hole angles. The wells are completed using dry trees from the TLP and are produced primarily from massive, fine-grained, Pleistocene reservoirs. These reservoirs require sand control to prevent sand production at the expected drawdowns planned during the life of the wells. To help ensure high-rate, long-life completions, the producing zones are frac packed. The average perforated interval during the initial completion program was 310 ft, with a maximum perforated interval of 571 ft. The typical production-casing string for the wells consists of 10¾-in. casing with an 8116-in. production liner. Drift diameter through the tapered production casing is 9½ and 6½ in., respectively. The 6½-in. drift diameter allows using common-sized screens and packers. The wells are generally completed with a 4½ × 3½ -in. tapered-tubing string. Premium screens with shunt tubes are used on the wells because of the long deviated intervals. The "frac-pack" stimulation treatments are pumped at rates of 27 to 40 bbl/min with a viscoelastic-surfactant (VES) carrier fluid. Washpipe-conveyed downhole-pressure and -temperature gauges and radioactive tracers are used to help analyze the treatment results. This paper will discuss screen-selection philosophy in silt/ very-fine-sand reservoirs, carrier-fluid selection, perforation strategy, and ability to frac across shale intervals. The paper also will cover the effectiveness of achieving a frac pack with premium screens with shunt tubes, on the basis of downhole-pressure and – temperature and radioactive-tracer information, and will discuss revised operational practices that resulted in zero- to negative-skin completions across long, perforated intervals, which continue to produce sand-free after extreme reservoir depletion.