Hi Harald & discussion group,
Have you perhaps considered the use of a Downhole Power Tool (DHPT)? This tool is an industry standard technique in the North Sea with over 700 runs and we are in the process of building scale to support the global market. The DHPT acts like a ‘Sub-Surface Casing Jack’ applying up to 1,400,000lbs of Pull Force directly above the Top of Casing with a 3ft stroke to jack free Casing (stuck by formation collapse barite fall out, other settled solids or partial cement) until the hook load is reduced to a point where the rig can take over and pull to surface. This eliminates the need for Jarring and limits loading of the Rig (also suitable for Rigless Applications) and mitigates the concern of friction losses of the workstring which can be significant in deep and deviated wells. Our latest offering is the Titan System which combines the force of DHPT with repeat and prescriptive cutting capability (Cut-Jack-Pull-Repeat) to allow for pulling the Casing in shorter sections ‘guaranteeing casing on deck’ which can save days when compared with milling with lower operational risk and no swarf handling concerns. I have attached some supporting material and please feel free to visit our website at www.ardyne.co or contact me at firstname.lastname@example.org
I have not used the NOV agitator for recovering casing but I have reviewed the use of the TIW casing pulling tool (CPT) for similar situations where casing recovering is difficult.
It may be worth your while investigating this technology and its availability in your area.