Environmental effects of drilling muds and cuttings

Abstract

From the Abstract: “In 1973, a Shell research group studied some of the environmental parameters concerning offshore drilling discharges. During a 2-day period in 1973, they collected 34 water samples around a Shell platform off the coast of Louisiana. Samples were taken at the surface, midwater (120 ft), and at the bottom (245 ft). The platform was actively drilling at the 9,000 ft. level with lime base mud at the time. Analyses were make for alkalinity, total dissolved solids, total suspended solids, total organic carbon, and total dissolved chromium. Results indicate that all parameters approached normal background levels as close as 60 yards to the platforms. Mid- and bottom-water samples beneath the platform showed some detectable chromium, but hexavalent chromium was not detected in any samples.

Theoretical dilution curves were estimated for a current of 0.5 feet per second and discharge rates of 40 and 250 barrels per hour. Dilutions of 1,000:1 were estimated at approximately 1,000 and 10,000 feet respectively.

The importance of environmental observations is stressed. M. E. A. Shinn, an experienced diver and underwater photographer, has observed marine life under Gulf of Mexico platforms for many years. He has observed that the light mud fractions appear to drift upward and laterally, while the cutting chips and filter cake fall straight to the bottom. Encrusting organisms are observed prolifically covering platform structures. Barnacles are seen living on and inside discharge downpipes. Fish swim through discharge material with no observable ill effects.

There appear to be no visual detrimental effects of drilling discharges to organisms that are living above the bottom. Cutting piles beneath production platforms have been observed to be repopulated with marine communities.”