Collaborative Research: Paleohydrology of the Illinois Basin--Effects of Glaciation on Fluid Flow, Solute Transport, and Microbial Methane Generation

在过去的200万年里，劳伦泰德冰盖的融化深刻地改变了北美的地下水和地表水文。 冰下融水沿沿着低洼古生代盆地边缘渗入含盐含水层，逆转地下水流方向，并将淡水-咸水混合带抑制到1公里以上的深度。 富含有机质的裂缝页岩中微生物甲烷的经济聚集位于沿着盆地边缘的淡水补给区。 我们将评估更新世冰川负荷和永久冻土发展的补给历史和流通的大气沃茨在伊利诺伊盆地的影响，集中在两个有机丰富的地区，含有微生物甲烷（晚泥盆世新奥尔巴尼页岩，宾夕法尼亚州的煤），和邻近的区域含水层系统。 本研究的结果将极大地扩展我们对冰盖-含水层相互作用、承压地下沃茨的年龄分布以及地下深部微生物活动的水文地球化学控制的理解。将从新奥尔巴尼页岩、宾夕法尼亚煤层气区和邻近区域含水层的约50个生产油/气井和家庭威尔斯中收集地层沃茨、气体和微生物样本。沿着一条从伊利诺斯盆地中部到盆地东北边缘的横断面。 我们将分析元素和稳定同位素（O、H、C）化学、14 C和地层沃茨和天然气的稀有气体。 此外，将通过DNA分析确定微生物种群，并将分析存档的页岩和煤材料的碳氢化合物生物降解情况。 我们最近开发了一种新的水文模型，它解决了流体运动，热量，多物种（盐度，稳定/放射性同位素，和惰性气体）溶质运移，永久冻土，岩石圈弯曲/地幔流方程。 该模型将被观察到的盐度和同位素示踪剂来测试的假设，冰盖动态已大大修改了管道的伊利诺伊盆地在晚更新世。尽管许多研究的古水文伊利诺伊盆地的维护高盐度流体的海洋起源的深盆地含水层仍然是谜。 这项研究将有助于限制盐水和淡水资源在沉积盆地的停留时间，以及驱动大陆规模的流体和溶质输送对抗强盐度梯度所需的水动力。 这项研究的结果也将有助于限制非常规储层（如裂缝性黑色页岩和煤层）中经济天然气聚集所需的水文和地球化学条件。 重要的是，这个多学科项目将是亚利桑那大学博士学位的一个组成部分。学生的论文，并涉及几个本科研究人员。

Melting of the Laurentide Ice Sheet profoundly altered the groundwater and surface hydrology of North America over the last 2 million years. Subglacial meltwaters infiltrated into saline aquifers along the margins of low-lying Paleozoic basins, reversing groundwater flow directions and suppressing the freshwater-saline water mixing zones to over 1 kilometer depth. Economic accumulations of microbial methane in fractured organic-rich shales are located in areas of freshwater recharge along the basin margins. We will assess the impact of Pleistocene glacial loading and permafrost development on recharge history and circulation of meteoric waters in the Illinois Basin, focusing on two organic-rich zones that contain microbial methane (Late Devonian New Albany Shale, Pennsylvanian coals), and adjacent regional aquifer systems. Results of this study will greatly expand our understanding of ice sheet-aquifer interactions, age distribution of confined groundwaters, and hydrogeochemical controls on microbial activity in the deep subsurface.Formation waters, gas, and microbial samples will be collected from ~50 producing oil/gas and household wells in the New Albany Shale, Pennsylvanian Coalbed Methane Play, and adjacent regional aquifers, along a transect from the central Illinois Basin to the northeastern basin margin. We will analyze the elemental and stable isotope (O,H,C) chemistry, 14C, and noble gases of formation waters and gas. In addition, microbial populations will be determined by DNA analyses, and archived shale and coal materials will be analyzed for biodegradation of hydrocarbons. We have recently developed a new hydrologic model, which solves equations for fluid motion, heat, multi-species (salinity, stable/radiometric isotope, and noble gas) solute transport, permafrost, and lithosphere flexure/mantle flow. This model will be compared to observed salinity and isotope tracers to test the hypothesis that ice sheet dynamics has substantially modified the plumbing of the Illinois Basin during the Late Pleistocene.Despite numerous studies of the paleohydrology of the Illinois Basin the maintenance of high salinity fluids of marine-origin in deep basin aquifers is still enigmatic. This study will help to constrain the residence times of brines and freshwater resources in sedimentary basins, and hydrodynamic forces required to drive continental-scale fluid and solute transport against strong salinity gradients. Results from this study will also help to constrain the hydrologic and geochemical conditions necessary for economic gas accumulation in unconventional reservoirs, such as fractured black shales and coalbeds. Importantly, this multi-disciplinary project will be an integral part of a University of Arizona Ph.D. student's thesis, and involve several undergraduate researchers.