Fate of Drilling Fluids during the South McMurdo Sound Project (SMS) of the Antarctic Geological Drilling Program (ANDRILL)

The PI proposes to utilize computer models used by hydrogeologists to establish the fate and transport of contamination and determine the extent of drilling fluid contamination in the ANDRILL SMS core. For these models, previously collected logs of lithology, porosity, fracture density, fracture type, fracture orientation, drilling fluid loss, drilling fluid characteristics and temperature will be used as input parameters. In addition, biodegradation and sorption constants for the drilling fluid will be determined and incorporated into the models. Samples of drilling fluids used during coring as well as the return fluids were collected at the drill site using standard microbiological sampling techniques. Fluids will be tested at in situ temperatures under aerobic and anaerobic conditions to determine biodegradation constants. Sorption will be determined between the drilling fluids and core samples using standard isotherm methods. Geochemical and microbial fingerprints of the fluids and the changes during biodegradation will determine the potential impact of the drilling fluids on the isolated microbial communities and the geochemistry within various subsurface lithologic units beneath the southern McMurdo Sound in Antarctica. The results of this study could potentially provide guidelines on developing less detrimental methods for future exploration, if deemed necessary through this research.
This proposed project will train a graduate student. The methods developed for analyses of samples in this project will serve as a guide for future studies of similar interest and will improve the understanding of ecological impacts of geologic drilling in Antarctica. The results of this study will be used as a reference for comparison with future studies examining newly developed, and improved, sample collection methods in future exploratory drilling projects in pristine environments. The PI is new to Antarctic research.

本项目首席研究员（Principal Investigator，PI）拟采用水文地质学家所用的计算机模型，以明确污染物的归趋与运移路径，并探明ANDRILL SMS岩芯中钻井液污染的波及范围。针对上述模型，前述已获取的岩性、孔隙度、裂缝密度、裂缝类型、裂缝走向、钻井液漏失量、钻井液特性及温度测井数据，将作为输入参数。此外，本研究还将测定钻井液的生物降解常数与吸附常数，并将其纳入模型体系。研究团队已采用标准微生物采样技术，在钻井现场采集了取心作业所用钻井液及返排液样本。将在原位温度下，分别在有氧与无氧环境中对流体样本开展测试，以确定其生物降解常数。吸附常数的测定将采用标准等温线法，通过钻井液与岩芯样本的吸附实验完成。通过分析流体的地球化学与微生物指纹图谱，以及生物降解过程中的特征变化，可明确钻井液对南极麦克默多湾南部地下各岩性单元内分离得到的微生物群落及地球化学环境的潜在影响。若本研究验证可行，其成果可为未来勘探开发中低危害性钻井作业方法的制定提供参考依据。
本拟议项目将培养一名研究生。本项目所开发的样本分析方法，可为后续同类研究提供借鉴，并有助于深化对南极地质钻探所带来生态影响的认知。本研究成果将作为参照，用于对比未来在未受扰动的原生（pristine）环境中开展的、针对新型改进型样本采集方法的相关勘探钻探研究。本项目首席研究员此前尚未涉足南极研究领域。