Loss circulation is the biggest challenge after drilling and weather-related problems during the process of constructing new wellbores. As per industry figures, more than USD 2 billion per year are spent in combating losses. In the Kohat-Potwar plateau of the Upper Indus basin of northern Pakistan, a harsh and complex environment, a well usually takes anywhere from 180 to 270 days to drill. The overall time taken to drill depends on the formation thicknesses, severity of the losses, and the concession location within northern Pakistan.
High-pressure water zones are located close to salt and shale formations, above the potential reservoirs. While drilling through the high-pressure formations, high mud weights greater than 1980 kg/m3 (16.5 lbm/gal) are required to maintain a well under control, which often leads to induced losses during drilling and also while running casing. The mud weight is typically lowered to 1500 kg/m3 (12.5 lbm/gal) or lighter to combat massive losses in naturally fractured limestone formations in the production hole.
Engineered fiber-based loss circulation (EFBLC) control pills, based on a specially engineered fiber system and the particle size distribution principle, were developed to control the losses. The pills were effective in curing losses during drilling and while cementing; prior to the introduction of the EFBLC pills, operators spent days in combating losses with numerous traditional methods. Also, the pills were robust enough to work in water-base mud (WBM), oil-base mud (OBM), or synthetic-base mud (SBM) environments with weights up to 2040 kg/m3 (17.0 lbm/gal).
In applications in northern Pakistan, the EFBLC pills were successful in combating the losses while drilling and cementing, thus reducing the threat of nonproductive time (NPT);minimizing the quality, health, safety and environmental (QHSE) concerns of well control; and preventing costly remedial jobs due to poor zonal isolation.