EPSRC project paper: New insights from 3D geological models at analogue CO2 storage sites in Lincolnshire and eastern Scotland, UK

Subsurface 3D geological models of aquifer and seal rock systems from two contrasting analogue sites have been created as the first step in an investigation into methodologies for geological storage of carbon dioxide in saline aquifers. Development of the models illustrates the utility of an integrated approach using digital techniques and expert geological knowledge to further geological understanding. The models visualize a faulted, gently dipping Permo-Triassic succession in Lincolnshire and a complex faulted and folded Devono-Carboniferous succession in eastern Scotland. The Permo-Triassic is present in the Lincolnshire model to depths of -2 km OD, and includes the aquifers of the Sherwood Sandstone and Rotliegendes groups. Model-derived thickness maps test and refine Permian palaeogeography, such as the location of a carbonate reef and its associated seaward slope, and the identification of aeolian dunes. Analysis of borehole core samples established average 2D porosity values for the Rotliegendes (16%) and Sherwood Sandstone (20%) groups, and the Zechstein (5%) and Mercia Mudstone (<10%) groups, which are favourable for aquifer and seal units respectively. Core sample analysis has revealed a complex but wellunderstood diagenetic history. Re-interpretation of newly reprocessed seismic data in eastern Scotland has significantly reduced interpretative uncertainty of aquifer and seal units at depths of up to -6 km OD in a complex faulted and folded Devonian-Carboniferous succession. Synthesis of diverse data in the 3D geological model defines a set of growth folds and faults indicative of active Visean to Westphalian dextral-strike slip, with no major changes in structural style throughout the Carboniferous, in contrast to some published tectonic models. Average 2D porosity values are 14-17% in aquifer units and <2% in the seal unit, with a ferroan dolomite cement occluding porosity at depth.

基于两个具有对比性的模拟地点，构建了承压含水层和封闭岩系的三维地质模型，作为探究碳 dioxide 在咸水含水层中地质储存方法的第一步。模型的开发展示了运用数字技术及专家地质知识进行综合研究，以深化地质理解的实用性。模型直观地描绘了林肯郡的断块、缓倾的侏罗纪-三叠纪地层序列，以及苏格兰东部的复杂断块和褶皱的志留纪-石炭纪地层序列。在林肯郡模型中，侏罗纪-三叠纪地层深度达 -2 公里 OD，包括雪伍德砂岩和罗蒂耶朗德组含水层。由模型得出的厚度图对石炭纪古地理进行了测试和细化，例如碳酸盐礁及其相关海向斜坡的位置，以及风成沙丘的识别。对钻孔岩心样品的分析确定了罗蒂耶朗德组（16%）和雪伍德砂岩组（20%）的平均二维孔隙率，以及泽奇斯坦组（5%）和梅西亚泥岩组（<10%）的平均二维孔隙率，这些孔隙率分别有利于含水层和封闭单元。岩心样品分析揭示了复杂但易于理解的成岩历史。对苏格兰东部新处理地震数据的重新解释，显著降低了在复杂的断块和褶皱的志留纪-石炭纪地层序列中，深度达 -6 公里 OD 的含水层和封闭单元的解释不确定性。3D 地质模型中多元数据的综合分析，定义了一套表示活动维斯尼亚至威斯特法利亚右旋走滑的生长褶皱和断层，与石炭纪期间结构风格的重大变化形成鲜明对比，这与一些已发表的构造模型不同。含水层单元的平均二维孔隙率为 14-17%，封闭单元的平均二维孔隙率小于 2%，深度处的孔隙被含铁白云石胶结物堵塞。