Idle bit lodged in swelling formation during water well drilling
A customer planning a 1,100-ft [335-m] stock water well had cemented
500 ft [152 m] of 5-in steel casing and continued drilling through the
surface pipe into the Niobrara chalk. When discontinuing drilling operations
for the weekend, the driller did not pull the bit into the casing but left the
tool at 580 ft [177 m]. The driller was using only native mud without
filtration control. However, without filtration control, the Niobrara Formation
swells when water is used for drilling operations. When attempting to resume
operations on Monday, the driller experienced circulation but could not rotate
or move the drillstring because the chalky formation had swollen.
Integrated solution deployed to free stuck drillstring
The driller mixed a viscosifier into the drilling fluid and circulated
it in the well for
2–3 hours. However, no cavings or cuttings were
returned to surface, and the bit was still stuck. M-I SWACO then recommended
running a mixture of RINGFREE thinner and PLATINUM ROD EASE lubricant to
displace the viscosifier mixture from inside the drillpipe. RINGFREE thinner
helped remove bentonite clays from the drillstring, and the thinner dissolved
rapidly. The PLATINUM ROD EASE lubricant was recommended because it reduces
torque and drag and lubricates all downhole consumables.
Product mix resolved problem, saved USD 40,600
The displacement was attempted by capping a smaller pipe off on one end
and running it 60 ft [18 m] inside the drillpipe. Afterward, approximately
2.5 galUS [9.5 L] of the RINGFREE thinner and PLATINUM ROD EASE lubricant
mixture was pumped into place but was not initially successful at loosening the
drillstring.
M-I SWACO then calculated the volume from the bit to the bottom of the
surface casing (63 galUS [238 L]) and the volume of the drillpipe, rig
plumbing, and mud pump (108 galUS [409 L]). A combination of 60 galUS [227 L]
of RINGFREE thinner and 20 galUS [76 L] of PLATINUM ROD EASE was mixed in a
small tank. This mixture was pumped down the drillpipe and allowed to set for 2
hours. After three hard pulls, the drillpipe was pulled loose and freed on the
fourth attempt.
The customer used 105 galUS [397 L] of MAX GEL viscosifier to flush the
RINGFREE thinner and PLATINUM ROD EASE lubricant from the hole and resumed
drilling with fresh fluid. On bottom, the customer used a fresh mix of MAX GEL
fluid and PLATINUM PAC lubricant to finish the well.
Total cost savings on the well was an estimated USD 30,600. Savings
included 9 days of labor, fuel cost, and rig time estimated at USD 1,000 per
day. Additional savings were assumed from forgoing the expense of replacing 500
ft of 5-in steel pipe and cement at a cost of USD 20 per foot—a total of
USD 10,000 for the well. The replacement cost for the 580-ft drillstring, subs,
and bit would have totaled USD 11,600 or USD 20 per foot. The customer is now
consistently using PLATINUM PAC lubricant to prevent drilling problems in the
swelling shale.
