Natural fractures prompt seven days of lost circulation
An operator was drilling an 8 1/2-in open hole section for a new well in
the Kohat-Potwar Plateau of the Upper Indus basin, a harsh and complex
environment, when natural fractures began to impede progress. Around 15,800 ft
[4,815 m], partial losses began but were managed with conventional mud lost
circulation material (LCM).
As the drilling continued, the well experienced a kick, which required
an increase in mud weight from 11.0 to 11.4 lbm/galUS [1.32 to 1.36
g/cm3]. This increased the losses, but again they were managed by
conventional mud system LCMs, including calcium carbonate and mica pills in
multiple particle sizes.
Near 16,500 ft [5,000 m], the well experienced total
losses—amounting to more than 2,000 bbl [318 m3] over 7 days.
Conventional LCMs were added to reduce the mud weight and stabilize the hole,
but drilling could not continue safely with the reduced mud weight, and
increasing it would immediately resume the losses.
The operator asked Schlumberger for a way to strengthen the formation
and plug the naturally fractured formation enough to resume drilling.
Expert software recommends composite pill
Schlumberger engineers turned to the Lost Circulation Control Advisor
software, an expert decision-tree application used to analyze and solve lost
circulation problems. Based on inputs of well fluid information, prior lost
circulation treatments, loss rates, and other well data, the software
recommends options to mitigate lost circulation.
For this well, the software recommended a Losseal Natural Fracture
treatment using a fit-for-purpose pill comprising a composite blend of fibers
and solids that create a strong impermeable grid, stopping mud or cement from
flowing into natural fractured zones.
