greatly) of the total cost of drilling a well, and demands competent mud engineers. Large cost savings result when the mud engineer and fluid performs adequately. The mud engineer is not to be confused with mudloggers, service personnel who monitor gas from the mud and collect well bore samples. Compliance engineer The compliance engineer is the most common name for a relatively new position in the oil field, emerging around 2002 due to new environmental regulations on synthetic mud in the United States. Previously, synthetic mud was regulated the same as water-based mud and could be disposed of in offshore waters due to low toxicity to marine organisms. New regulations restrict the amount of synthetic oil that can be discharged. These new regulations created a significant burden in the form of tests needed to determine the "ROC" or retention on cuttings, sampling to determine the percentage of crude oil in the drilling mud, and extensive documentation. No type of oil/synthetic based mud (or drilled cuttings contaminated with OBM/SBM) may be dumped in the North Sea. Contaminated mud must either be shipped back to shore in skips or processed on the rigs. A new monthly toxicity test is also now performed to determine sediment toxicity, using the amphipod Leptocheirus plumulosus. Various concentrations of the drilling mud are added to the environment of captive L. plumulosus to determine its effect on the animals. The test is controversial for two reasons: These animals are not native to many of the areas regulated by them, including the Gulf of Mexico The test has a very large standard deviation, and samples that fail badly may pass easily upon retesting See also Directional drilling Driller (oil) Drilling fluid decanter centrifuge Drilling rig Formation evaluation Landfarming Mud Gas Separator Mud systems MWD (measurement while drilling) Oil well control Roughneck Underbalanced drilling References Further reading ASME Shale Shaker Committee (2005). The Drilling Fluids Processing Handbook. . Kate Van Dyke (1998). Drilling Fluids, Mud Pumps, and Conditioning Equipment. G. V. Chilingarian & P. Vorabutr (1983). Drilling and Drilling Fluids. G. R. Gray, H. C. H. Darley, & W. F. Rogers (1980). The Composition and Properties of Oil Well Drilling Fluids. DCS Shale Shaker SUPPLIER. The Drilling Fluids cleaning system. Drilling technology