当前位置: X-MOL 学术Sedimentology › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Focused methane migration formed pipe structures in permeable sandstones: Insights from uncrewed aerial vehicle-based digital outcrop analysis in Varna, Bulgaria
Sedimentology ( IF 3.5 ) Pub Date : 2021-03-24 , DOI: 10.1111/sed.12871
Christoph BÖttner 1 , Ben J. Callow 2 , Bettina Schramm 1 , Felix Gross 3 , Jacob Geersen 1 , Mark Schmidt 1 , Atanas Vasilev 4 , Petar Petsinski 4 , Christian Berndt 1
Affiliation  

Focused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localized overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (ca 15 km west of Varna, Bulgaria) reveal large carbonate-cemented conduits, which formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. An uncrewed aerial vehicle with an RGB sensor camera produces ortho-rectified image mosaics, digital elevation models and point clouds of the two kilometre-scale outcrop areas. Based on these data, geological field observations and petrological analysis of rock/core samples, fractures and vertical fluid conduits were mapped and analyzed with centimetre accuracy. The results show that both outcrops comprise several hundred carbonate-cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding-parallel calcite cemented interbeds which differ from the hosting sand formation only by their increased amount of cementation. The observations show that carbonate precipitation likely initiated around areas of focused fluid flow, where methane entered the formation from the underlying fractured subsurface. These first carbonates formed the outer walls of the pipes and continued to grow inward, leading to self-sustaining and self-reinforcing focused fluid flow. The results, supported by literature-based carbon and oxygen isotope analyses of the carbonates, indicate that ambient seawater and advected fresh/brackish water were involved in the carbonate precipitation by microbial methane oxidation. Similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand-dominated formations, which has wide implications for the understanding of how focusing of fluids works in sedimentary basins with broad consequences for the migration of water, oil and gas.

中文翻译:

可渗透砂岩中集中的甲烷迁移形成管道结构:来自保加利亚瓦尔纳无人驾驶飞行器数字露头分析的见解

集中的流体流动通过跨地质构造传递流体和压力来塑造海洋沉积盆地的演化。垂直流体管道可在局部超压突破盖层(渗透屏障)并由此将超压流体输送至较浅的储层或地表的地方形成。Pobiti Kamani 和 Beloslav 采石场始新世流体流动系统的野外露头(保加利亚瓦尔纳以西 15 公里处)揭示了大型碳酸盐胶结管道,这些管道形成于特提斯边缘北部高渗透性、松散的海砂中。配备 RGB 传感器相机的无人驾驶飞行器可生成两公里尺度露头区域的正射校正图像马赛克、数字高程模型和点云。基于这些数据,以厘米精度绘制和分析岩石/岩心样本、裂缝和垂直流体管道的地质野外观察和岩石学分析。结果表明,两个露头都包含数百条垂直于层理定向的碳酸盐胶结流体管道(管)和至少七个平行于层理的方解石胶结夹层,这些夹层与承载砂岩地层的区别仅在于它们的胶结量增加。观察结果表明,碳酸盐沉淀很可能在集中流体流动区域周围开始,其中甲烷从下面的裂缝地下进入地层。这些最初的碳酸盐形成了管道的外壁,并继续向内生长,导致自我维持和自我增强的集中流体流动。结果得到碳酸盐的基于文献的碳和氧同位素分析的支持,表明环境海水和平流淡水/微咸水参与了微生物甲烷氧化的碳酸盐沉淀。类似的结构也可能在现代环境中形成,其中集中的流体流动将流体平流到上覆的以砂为主的地层中,
更新日期:2021-03-24
down
wechat
bug