Sarawak Shell Berhad and Sabah Shell Petroleum Co Ltd are companies of the Royal Dutch/Shell group of companies operating in Malaysia under a Production Sharing Contract arrangement. Current drilling activities are located offshore the states of Sarawak and Sabah. Due to difficult downhole drilling conditions, the use of synthetic based mud's have become increasingly more important.

In 2005-6, several deepwater locations will be drilled using non-aqueous based drilling fluids. Of key interest is the availability of paraffin base stock from Shell MDS (Malaysia Sdn Bhd.’s plant in Bintulu). Paraffin based systems are currently in use and found to be effective by other operators in the area. Because paraffins do not currently meet all US EPA laboratory test criteria (toxicity and biodegradability), there is a strong interest in collecting actual field data to assess the environmental fate of such discharges. Shell Malaysia is embarking on a unique field study program to assess the fate of the paraffin based mud's and cuttings in water depths ranging from 300-1,500 m and to compare the data to similar studies with internal olefin mud's.

Shell Global Solutions International B.V., with experience in SBM's and deepwater environmental monitoring, had designed an approach to answer the key questions. The primary local contractor on the project is Petronas Research and Scientific Services Sdn. Bhd. (PRSS). Metocean data from the study area is being used, in conjunction with a state of the art drill mud dispersion model to predict the 3-D accumulation of the cuttings and mud on the seafloor. Gas chromatographic techniques (GC-FID) will be used for identifying and quantifying the presence of paraffins in the marine sediments. Ecological risk methodologies are being used to predict potential benthic impacts. Each of four drilling locations will be sampled post drilling and one year later. This will provide important insight into the weathering rates of paraffins in sediments.

The study design, methods to be employed, and preliminary modeling and ecorisk evaluations are presented and discussed in the paper.

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