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
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.
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