Performance Report: BLACK FURY Enhances Wellbore Stability and Reduces Number of Trips

Poza Rica, Veracruz, Mexico

Challenge: An operator drilling 9½-in. holes in the Pozo Rica district of Mexico encountered problems with inhibitive muds, problems with extra short trips, stuck logging tools and difficult casing runs. In one well, a 9½-in. bit was made up with a directional bottomhole assembly (BHA) and was run into the hole. The drilling team drilled out cement from 335 to 1,667 ft (102 to 505 m), circulated the hole clean and pulled the BHA to surface. Wireline logs were run in the hole, but could not pass beyond 1,362 ft (415 m), so the tool was pulled out of the hole and a bit made up for a check trip. Once the bit was on bottom, two high-viscosity pills were pumped and circulated out to clean the wellbore before tripping pipe.

Solution: The Poza Rica District team made a technical proposal to minimize the problems for the 9½-in. hole. The team designed a water-base mud formulation to assure hole stability and eliminate short trips. Studies of the interaction between rock and fluid on cuttings samples from the Agua Fría and Coapechaca fields at the laboratory (Laboratorio Central Veracruz) defined the shales as dispersive rather than swelling. Based on this information, the team proposed a water-base mud system that would reduce the amount of dispersion in the claystones found above 1,667 ft (500 m).

The BLACK FURY product was selected as an additive for hole stability and to help reduce dispersion of water sensitive shales. During the laboratory testing with the BLACK FURY product, the fluid showed 80% of recovered material in the dispersion test. This led the operations staff to propose the application of a new inhibitive polymeric mud with the BLACK FURY (10 L/m3) product.

Result: During the drilling of the 9½-in. hole on the second well, there were no torque problems, the cuttings appeared to be inhibited and no gumbo attacks blinded the shaker screens or plugged flow lines. At the end of the interval, the wireline logs and the casing run were completed without problems. A short trip was not required to stabilize the hole. Washout was minimal.

The Details

During the drilling of the 9½-in. hole on the second well, there were no torque problems, the cuttings appeared to be inhibited and no gumbo attacks blinded the shaker screens or plugged flow lines. At the end of the interval, the wireline logs and the casing run were completed without problems. A short trip was not required to stabilize the hole. Washout was minimal.

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