The toxicity effects of water based mud with different additives on aquatic life

Water based muds (WBMs) are by far the most commonly used muds, both onshore and offshore. It can be provided with various additives, such as fluid loss control agents, corrosion inhibitors, weighting materials, and viscosifiers, to develop the key properties of the mud to meet some functional requirements. Even though the overall environmental impact of mud additives in WBMs is minimal, it can contaminate and harm the marine life that inhabits the surrounding waters where drilling operation take place. A state environmental agency designated by EPA, regulates discharges of drilling muds and cuttings to state and federal waters of the U.S. Current National Pollutant Discharge Elimination System (NPDES) permits allow discharge of WBM and cuttings to federal, but not state, waters if they meet restrictions in the Effluent Limitation Guidelines (ELG) 1. Drilling and operating companies nowadays have been forced to review their mud additives selection guidelines to control the use of non-environmentally friendly and toxic mud additives in the formulation of WBMs. It is important to take account of environmental factors to eliminate any environmental impact. Therefore, experiments were conducted by using several of WBMs additives which are Barite, Potassium Chloride, Hydro Pac, CMC, Hydrozan and Guar Gum to determine their toxicity on aquatic life in which the test organisms for this research are Guppy fish and Neon Tetra fish. The procedure for toxicity test for this study follows the standard procedure recommended by US EPA. In this experiment the test organisms were exposed to the WBM that contain drilling fluid additives with three different concentrations of contaminants for 96 hours. The numbers of survived organisms at the observation time were recorded. From the results obtained, clearly there are no significant effects on aquatic life after being exposed to each drilling fluid additives. Thus the LC50 value for all additives that being tested is above 50000ppm. This means that all these additives are considered non-toxic and environmentally friendly.