Abstract
GTL (Gas-to-Liquid) drilling base fluids, such as Shell GTL Saraline™ 185V/NEOFLO™ 4633, are synthetic hydrocarbons produced via Fischer-Tropsch synthesis from natural gas. GTL Fluids are predominantly comprised of iso- and normal paraffins and contain virtually no aromatics or contaminants such as sulphur and amines. Saraline 185V is a Health, Safety, Security, and Environmental (HSSE)- advantaged base fluid for use in global exploration and production drilling operations onshore and offshore.
Extensive terrestrial, freshwater and marine ecotoxicity testing with Saraline 185V and related GTL Fluids confirm a lack of acute or significant chronic toxicity to a wide range of environmentally relevant organisms. Saraline 185V is also readily biodegradable in aerobic freshwater, seawater, soil and sediments and will also degrade under anaerobic conditions. The biodegradability can be exploited to bioremediate drill cuttings, as has been demonstrated in both laboratory and field trials. Furthermore, when used offshore, marine benthic surveys have demonstrated that degradation also occurs and that there is a lack of any significant environmental impact associated with the discharge of Saraline 185V contaminated drill cuttings.
Extensive mammalian toxicity testing of GTL Products indicates that Saraline 185V will exert very little, if any, toxicity in mammalian species. Saraline 185V is odourless, and vapour emission tests reveal that it has >7-fold lower gas emissions when compared to conventional diesel, thereby leading to better air quality on drilling locations. A recent study which assessed emission and personal exposure levels to various hydrocarbons at key phases of drilling operations confirmed that significantly lower hydrocarbon exposures occurred for mud systems based on Saraline 185V compared to conventional diesel.
The drilling performance of GTL versus diesel based muds has also been assessed in an onshore drilling operations study. To enable a fair comparison all wells were drilled in the same formation (located in the Permian Basin of West Texas) using the same drilling rig, crews, bit, footage, fluid contractor, tools and directional driller. These field trial data indicated an overall drilling improvement for GTL over diesel mud.
This paper provides an overview of the exposure, human health, environmental and performance studies conducted on GTL drilling fluids. In combination, these create a value proposition for GTL Fluids showing that better health management combined with reduced environmental footprint and improved drilling and equipment performance leads to lower total well costs.
