勇払油ガス田〜あけぼの地区におけるスルーチュービング改修作業

Abstract

Japex did the workover operations in Yufutsu gas field, Hokkaido in 2004. It was an unique and challenging workover operations. The well had been suspended because more than 3,500m of 1.25in coiled tubing was left in 3.5in production tubing. This well had to be stimulated due to the damage of reservoir, so the coiled tubing must be retrieved prior to stimulation. The situation was very serious because of the narrow annulus of the string, so selection of the pipe and tool size were restricted, accordingly the yield strength of such macaroni pipe and tools were so weak. After an examination, the plan was made to retrieve the coiled tubing from inside of 3.5in production tubing by using 1.9in work tubing, thru-tubing fishing tool and slim-hole wireline tools. This operations were performed by drilling rig in case of contingency.Wireline chemical cutter was one of the key tools in our program. Unfortunately it was not working properly so we abandoned to use it and change the plan to swallow the coiled tubing with continuous overshot and 1.9in work tubing. Continuous overshot made an excellent progress and almost all the coiled tubing was retrieved from the well. Then the well was circulated and cleaned with brine, the operation was done in the budget.Stimulation was performed in April, 2005, as a result, productivity was improved substantially and this project was completed successfully.