Directional cavern wells, challenge and ways to optimization

The cavern storage site in the structure Kraak of HEINGAS Hamburger Gaswerke GMBH is located approximately 20 km south from Schwerin. Two of the three storage wells are deviated, S-shaped wells for economic and environmental reasons. A maximum displacement of 308 m has yet been achieved with the kick off point at 60 m (TVD) and the end of drop at 780 m (TVD). The first build up section to 35 at 367 m was done with a 23 bit in combination with a 11 3/4 positive displacement motor through loose, medium to fine sand. A mobile drilling rig was used. The article deals with the objectives, the lithology, the technical requirements and the results of the drilling operations. The results promise good chances for exceeding the achieved displacement fairly beyond 310 m thus increasing the build up rate of the building section to be drilled with 23 or even 24 bit for the casing setting depth of the 18 5/8 surface casing. Time and costs are saved if a bit of big dimension can be used to drill the hole for the 18 5/8 surface casing instead of drilling a pilot hole and opening the hole afterwards.