Life Cycle Assessment of Oil and Gas Drilling Activities

Abstract

Abstract A Life Cycle Assessment (LCA) study is presented for the comparative evaluation of environmental performance across different drilling scenarios, in the context of offshore oil and gas well operations. Particular emphasis is placed on offshore and land pathways for treatment and final disposal of drilling fluids and cuttings. The LCA model was developed in accordance with ISO 14040 and 14044 standards, encompassing distinct life cycle stages: fluids manufacturing, inbound logistics, drilling operations, outbound logistics, and end-of-life treatment and disposal. Six scenarios, involving diverse combinations of water-based (WBDF) and non-aqueous (NADF) drilling fluids, and three end-of-life alternatives—offshore disposal, industrial landfill, and incineration—were systematically assessed and compared. The Life Cycle Impact Assessment (LCIA) method employed was ReCiPe (H) Midpoint 2016, and the considered impact categories were climate change, particulate matter formation, freshwater eutrophication, marine eutrophication, freshwater ecotoxicity, and marine ecotoxicity. Among the lifecycle processes, logistic operations were found to have the lowest environmental impacts across all categories. The drilling phase exhibited significant influence, particularly in climate change and particulate matter formation. The fluid formulation phase, specifically in scenarios involving WBDF, prominently affected both freshwater eutrophication, marine eutrophication, and freshwater ecotoxicity. Marine ecotoxicity was mostly influenced by the end-of-life stage in scenarios involving offshore disposal. For five of the six impact categories, the scenario with the best overall environmental performance was drilling with NADF and offshore cuttings disposal, due to the greater performance of this type of fluid in drilling processes and the reduction in environmental impacts associated with avoiding onshore treatment and final disposal. Conversely, the discharge of cuttings into the sea had a pronounced impact on the marine ecotoxicity category due to the potential toxicity of substances such as copper, barium, and zinc. Among terrestrial treatment options, scenarios involving incineration were consistently more environmentally impactful across all impact categories. The findings of this LCA study offer a robust technical-scientific foundation, facilitating informed discussions and aiding decision-making processes regarding the environmental impacts of oil well drilling operations. This pertains particularly to the choice of drilling fluids and the management of drilling waste within this industry sector.