Many large wells have been drilled in the Gulf of Mexico's Lower Tertiary play. These wells are completed with single-trip multizone systems, and they have gross perforated lengths exceeding 1,500 ft. The main difficulty in perforating these wells is the high-pressure environment (~20,000 psi). Under these conditions, the challenges are to create sufficiently large entrance holes in the casing, minimize the high-risk of equipment damage due to gunshock, and minimize 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 one trip saves time and reduces risks when compared with stacked 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 non-productive 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 contain all the metallic components, 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-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 three perforating runs per well, saving approximately 9.2 days per well while minimizing personnel exposure. By perforating the largest 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%.