Erosion in gas wells caused by sand producing formations can result in severe operational issues leading to the degradation of surface and downhole equipment and the shutdown of production facilities at surface.
Old cased hole wells in highly unconsolidated, poorly sorted sandstone formations require robust sand control. In such instances, conventional gravel packing methods are not always possible and the installation and maintenance of downhole sand control throughout the well life can be challenging. In gas wells where sand velocities are high, the supporting metallic material being used in, for example standalone sand control screens is subject to plugging and subsequent rapid wear because of its low resistance to erosion. Hence the longevity of metallic sand control equipment is poor and frequent expensive re-completions and workovers are required.
An innovative solution using ceramic screens was used in an existing gas well in Bolivia, South America. The well geometry included double casing with sub-optimal cement across the target zone and, due to the complexity of voids behind the casing, it was not possible to perform the initial option of a cased-hole gravel pack. In addition to sand control the completion required mechanical zonal isolation to prevent water ingress at a later stage. In summary the project involved removing the existing completion, isolating deeper lying depleted producing zones, clearing the casing of debris, re-perforating the casing, installing a new completion with ceramic screens and zonal isolation valves.
BG Group in conjunction with German ceramics manufacturer ESK developed over a period of 18 months a series of ceramic sand control screens and sliding sleeve protections that provided a downhole sand control completion solution complete with mechanical water isolation.
The successful project exceeded all expectations and to date the well has produced sand free. The operational time and re-completion costs were less than of a cased-hole gravel pack, the operation much simpler and safer.
BG are now working on a project to use this innovative technology as a thru-tubing sand control solution for existing high rate gas wells offshore worldwide where open hole or cased hole gravel packs have failed.
Sand control has always been a challenge for BG-Group when developing its gas condensate sandstone reservoirs. Experiences with degradation of surface & downhole equipment have shown that erosion is a severe operational issue and can be a major production constraint.
Several sand control methods, such as conventional gravel packing and metallic standalone screens, have been applied by BG Group in Bolivia, South America. On September 2012 a workover was carried out in well X, one of the gas condensate wells in field Z operated by BG-Group in Bolivia's Chaco Plains Region. The main objectives for this workover were to isolate depleted deeper lying gas condensate reservoirs B and C and produce from the shallower virgin sandstone reservoir A using a completion design which would allow for simultaneous sand control and mechanical zonal isolation for water ingress prevention.
