Eliminating or controlling lost circulation during drilling or cement operations is a costly and time-consuming process. Traditional treatments include lost circulation materials (LCM), cement, crosslinked polymers, dilatent slurries, reinforcing plugs, and silicate systems. The general practice is to cure the losses before proceeding to the cementing operation. The mixed results of such treatments plus the fact that cementing operations sometimes proceed even with partial or total losses have led to the development of a new advanced-fiber cement system (AFCS). This paper will discuss the properties and the mechanism of the AFCS and its successful applications as a solution to lost circulation in the Middle East and the Far East.
AFCS forms a fibrous network across highly permeable formations, induced and natural fractures, and vugular formations to prevent and stop the losses during remedial or primary cementing operations. Unlike conventional fibers that normally are difficult to disperse in the cement slurries and tend to plug surface and downhole equipment, AFCS does not suffer from such drawbacks.
Laboratory tests have shown the effectiveness of AFCS in plugging different hole sizes. The efficiency of this system was enhanced in the laboratory when combined with high-performance lightweight cement slurry (HPLW), an optimized particle size distribution system. Several jobs in Abu Dhabi showed substantial success rates compared with traditional lost-circulation treatments. This was confirmed by cement returns to surface and cement coverage across the lost-circulation zones.
Other field locations utilized AFCS in cement plugs, top jobs, and primary cementing operations through different float equipment, liner hangers, and even coiled tubing without any plugging problems.