Schlumberger

Performance Report: HDD Mud System Paves Way for World Blind Shaft Drilling Record (Illinois)

Challenge: Bentonite was being used to drill the first injection well on a four-well project. From the point where surface casing was set, hole problems began. The surface casing had to be reset and cemented three times due to drilling fluid migrating up outside of the surface pipe. Following further drilling challenges, logging indicated that the hole had swollen to 24 in. because of highly reactive clays.

Solution: M-I SWACO engineers were asked to prepare a mud program with additives that would prove effective in inhibiting clay swelling. The following additives were recommended for use on both injection and monitor wells: MAX GEL, POLY PLUS, PLATINUM PAC UL, RINGFREE, and POLY PLUS LV additives.

Result: The client realized a $425,000 drilling time savings on injection Well No. 2 as compared to injection Well No. 1 and realized as much as $175,000 in rig time on monitor Well No. 1. The monitor well was drilled using the same mud program as injection Well No. 2 and no hole, fluid or gauge issues were encountered. When M-I SWACO engineers arrived on the four-well project site, the client was preparing to drill out the cement from the 50-ft (15-m) surface hole on an injection well. The drilling fluid, heavily contaminated with calcium from the cement, was treated with PLATINUM PAC UL additive and soda ash and the cement was drilled out. The 46-in. hole was drilled to a depth of 500 ft ( 152 m) with no fluid issues, except the need to deviate from the fluid program slightly and increase the yield point to 30 cP and the fluid density to 9.0 lb/gal (4 kg/L) to prevent caving in the sugar sands found to be deeper than expected. The 46-in. hole was then logged and found to be of correct gauge, no swelling; the 34-in. casing was run and cemented with no fluid. The cement was drilled out of the 34-in. casing and while maintaining a water loss less than 7. At about 950 ft (290 m) POLY PLUS LV shale inhibitor/viscosifier was introduced into the fluid system. The well was logged and found to be at gauge, casing was run and cemented with no fluid issues. The client drilled the final stage to 1,490 ft (454 m) in 32½-in. hole. The well was logged and found to be at gauge and the 24-in. casing was run. Additional drilling was done with reverse air.

The gyp/lime was made up, but owing to space constraints of the earthen mud pit only 65% of the necessary volume or roughly 94,000 bbl would be available for use. Industry standard called for 2 ½ times the finished hole volume of fluid for weighting up, which in this case would have been 144,000 bbl.

Drilling proceeded to 172 ft (52.4 m) when the crossover sub between the drill pipe and the bottom hole assembly failed leaving the 522,000 lb (236,775 kg) BHA at the bottom of the hole. FKC was concerned the hole would deteriorate and stick the BHA before fishing tools large enough to retrieve the drilling assembly. However, the highly inhibitive characteristics of the gyp/lime system prevented hole sloughing, and squeezing thus retrieval was completed trouble free, allowing the sub to be repaired and returned to service.

Later, the drilled hole had to remain static for 28 days while awaiting bit repairs. FKC expected severe sloughing shale and tight hole conditions when tripping back into the shaft; however, little or zero tight hole was encountered.

Fluid parameters were maintained as programmed throughout the shaft drilling project with the calcium level, the filtrate, as well as Viscosity maintained daily within the set parameters of the fluid program. Mud density held at 8.4 lb/gal without the use of solids control equipment and fluid circulation was maintained at 5,800-6,400 gpm with 110-155 psi air pressure to insure adequate hole cleaning.

The M-I SWACO HDD gyp/lime fluid system exceeded all of the contractor’s expectations for this high-profile blind shaft drilling project.

  • Established world drilling record for 20 ft (6.1 m) diameter, 980 ft (298.7 m) blind shaft
  • No bit balling encountered
  • Eliminated fluid-related trips
  • No tight holes observed even with prolonged static periods
  • Considerably reduced time and costs

Download: HDD Mud System Paves Way for World Blind Shaft Drilling Record (0.20 MB PDF)

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