Decrease transportation and discarding costs by enabling compliant overboard disposal

Atwood Oceanics was drilling offshore in the Gulf of Mexico, where regulations require using a centrifuge and dryer to treat cuttings that will be disposed overboard. A sample of cuttings from each piece of equipment must be tested every 500 ft [152 m] and analyzed with a mass-balance retort. These results are then used to calculate the well's average ROC, which must remain below 6.9% for overboard disposal.

If the ROC is too close to the regulatory requirement, drilled cuttings are sent to a cuttings box, causing increased rig time and expenses on shipping and disposal as well as restricting the ROP to the available volume in the cuttings boxes on the location in a given time. During cuttings treatment, however, if the discharge from the dryer is too dry, there will be issues with sticking and equipment packoff.

Deploy reduced-footprint COMPACT VERTI-G low-profile cuttings dryer

The operator requested that M-I SWACO install its COMPACT VERTI-G low-profile cuttings dryer on its Advantage rig in the Gulf of Mexico. The COMPACT VERTI-G dryer is a high-capacity vertical centrifuge with a screen mesh basket and dedicated centrifuge to help reclaim more fluid. With a maximum drying rate of 61 metric tons per hour, the COMPACT VERTI-G dryer dries cuttings to less than 5% ROC, reducing the volume of discarded waste.

The dryer includes hard-faced, adjustable, rotating flights that brush cuttings to the screen surface, helping to prevent blinding and decrease potential downtime. This separation is achieved by strategically deploying 327 gn [3,206 m/s2] at the base of the cone to keep solids moving through the system and also by spending more time in the fluid-removal stage of the treatment compared with conventional drying techniques.

Enable offshore disposal, save USD 127,740 in costs

In the first 2 1/2 months after its installation, the COMPACT VERTI-G dryer achieved an average ROC of 1.77%. With the dryer in place, clean drilling fluid flowed from the unit at approximately 10 galUS/min [38 L/min], maintaining a steady flow returning to the active system.

In a 21-in hole section of a similar well in this field, a different cuttings dryer was producing an ROC of about 2.63%. In the subject well, the 3,694-ft [1,126-m] 21-in hole section was underreamed at an ROP of 80 ft/h [24 m/h] and an average ROC of 1.33%. Additionally, 398 bbl of 12-lbm/galUS [1.43-g/cm3] drilling fluid was reclaimed in the section.

In just that section, the fluid recovery from the COMPACT VERTI-G dryer saved Atwood Oceanics USD 11,940 in transportation and handling costs and USD 115,800 in whole mud volume. Over the 2 1/2 months, the dryer also did not require shutting down for cleaning, which would lead to slower drilling and limited volume availability.