The largest deepwater wells in the Gulf of Mexico have been drilled in the Lower Tertiary play. Most of these wells are completed with single-trip multizone systems have gross perforated lengths exceeding 1,500 ft. The main difficulty in perforating these wells is the ~20,000 psi high-pressure environment. Under these conditions, the challenges include creating sufficiently large entrance holes in the casing, minimizing the high-risk of equipment damage due to gunshock, and reducing the amount of perforating debris created.
Perforating several intervals in a single run is required to complement single-trip multizone systems. Perforating all zones simultaneously in a single trip saves time and reduces risk when compared with stacked frac-pack completions requiring multiple trips for each zone. Safety and cost reduction are extremely important in deepwater operations. Risk control is very important because gunshock and/or debris problems can lead to multimillion dollar losses in nonproductive time, and in extreme cases, gunshock problems can lead to lost wells.
To undertake these challenges, a new Low Perforating Shock and Debris (LPSD) gun system was used. In comparison with standard high-pressure guns, the LPSD gun system produces much less gunshock and negligible amounts of debris; thus, minimizing gunshock risk and reducing cleanup runs typically needed to recover perforating debris. LPSD guns produce negligible amounts of debris because LPSD guns retain all the metallic components inside the guns, including the shaped charge cases, which remain virtually intact inside of the guns. A key element in planning these perforating jobs is gunshock prediction to evaluate if the equipment will be able to withstand the transient loads produced by the perforating guns. The gunshock prediction process is described in detail in this paper.
For a typical 4- to 6-zone 1,500 ft gross length perforating job, the time needed from picking up the first gun to laying out the last gun averages 84 hours. All zones are simultaneously perforated, which eliminates at least three perforating runs per well, saving approximately 9.2 days per well while minimizing personnel exposure. By perforating the largest deepwater high-pressure wells in the Gulf of Mexico's Lower-Tertiary play with LPSD guns, we minimized personnel exposure, minimized debris and reduced execution time up to 72%.