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Understanding sub-seabed fluid flow mechanisms is important for determining their significance for ocean chemistry and to define fluid pathways above sub-seafloor CO2 storage reservoirs. Many active seabed fluid flow structures are associated with seismic chimneys or pipes, but the processes linking structures at depth with the seabed are poorly understood. We use seismic anisotropy techniques applied to ocean bottom seismometer (OBS) data, together with seismic reflection profiles and core data, to determine the nature of fluid pathways in the top tens of meters of marine sediments beneath the Scanner pockmark in the North Sea. The Scanner pockmark is 22 m deep, 900 m × 450 m wide and is actively venting methane. It lies above a chimney imaged on seismic reflection data down to ∼1 km depth. We investigate azimuthal anisotropy within the Scanner pockmark and at a nearby reference site in relatively undisturbed sediments, using the PS converted (C-) waves from a GI gun source, recorded by the OBS network. Shear-wave splitting is observed on an OBS located within the pockmark, and on another OBS nearby, whereas no such splitting is observed on 23 other instruments, positioned both around the pockmark, and at an undisturbed reference site. The OBSs that show anisotropy have radial and transverse components imaging a shallow phase (55–65 ms TWT after the seabed) consistent with PS conversion at 4–5 m depth. Azimuth stacks of the transverse component show amplitude nulls at 70° and 160°N, marking the symmetry axes of anisotropy and indicating potential fracture orientations. Hydraulic connection with underlying, over pressured gas charged sediment has caused gas conduits to open, either perpendicular to the regional minimum horizontal stress at 150–160 N or aligned with a local stress gradient at 50–60 N. This study reports the first observation of very shallow anisotropy associated with active methane venting.

Evaluation of seismic reflection data has identified the presence of fluid escape structures cross-cutting overburden stratigraphy within sedimentary basins globally. Seismically-imaged chimneys/pipes are considered to be possible pathways for fluid flow, which may hydraulically connect deeper strata to the seabed. These fluid migration pathways through the overburden must be constrained to enable secure, long-term subsurface carbon dioxide (CO2) storage. We have investigated a site of natural active fluid escape in the North Sea, the Scanner Pockmark Complex, to determine the physical characteristics of focused fluid conduits, and how they control fluid flow. Here we show that a multi-scale, multi disciplinary experimental approach is required for complete characterisation of fluid escape structures. Geophysical techniques are necessary to resolve fracture geometry and subsurface structure (e.g., multifrequency seismics) and physical parameters of sediments (e.g., controlled source electromagnetics) across length scales (m to km). At smaller (mm to cm) scales, sediment cores were sampled directly and their physical and chemical properties assessed using laboratory-based methods. Numerical modelling approaches bridge the resolution gap, though their validity is dependent on calibration and constraint from field and laboratory experimental data. Further, time-lapse seismic and acoustic methods capable of resolving temporal changes are key for determining fluid flux. Future optimisation of experiment resource use may be facilitated by the installation of permanent seabed infrastructure, and replacement of manual data processing with automated workflows. This study can be used to inform measurement, monitoring and verification workflows that will assist policymaking, regulation, and best practice for CO2 subsurface storage operations.

Focused fluid flow shapes the evolution of marine sedimentary basins by transferring fluids and pressure across geological formations. Vertical fluid conduits may form where localised overpressure breaches a cap rock (permeability barrier) and thereby transports overpressured fluids towards shallower reservoirs or the surface. Here, we study field outcrops of an Eocene fluid flow system at Pobiti Kamani and Beloslav Quarry (~15 km West of Varna, Bulgaria), where large carbonate-cemented conduits formed in highly permeable, unconsolidated, marine sands of the northern Tethys Margin. Using an uncrewed aerial vehicle with an RGB sensor camera we produced ortho-rectified image mosaics, digital elevation models, and point clouds of the two km-scale outcrop areas. Based on these data, geological field observations, and petrological analysis of rock/core samples, we mapped and analysed fractures and vertical fluid conduits with centimetre accuracy. Our results show that both outcrops comprise several hundred carbonate-cemented fluid conduits (pipes), oriented perpendicular to bedding, and at least seven bedding-parallel carbonate interbeds which differ from the hosting sand formation only by their increased amount of cementation. From these observations, we conclude 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. Our 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. We propose that similar structures may also form in modern settings where focused fluid flow advects fluids into overlying sand-dominated formations, which has wide

There has been a lot of research done by the Sugar Yield Decline Joint Venture providing insights and recommendations on how to improve the farming system to combat yield decline in cane fields. This paper explores a cane farming family's experience with implementing practices advocated by the YDJV and describes the changes they have made to their farming system. This description includes the specific practices that they were using before implementing the recommendations, the changes they have made, and the economic, environmental and social impacts that these have had on their business. The new farming system includes controlled traffic, reduced tillage, peanut rotation, flood irrigation from new on-farm storage, with GPS technology linked to land levelling, planting, harvesting and fertiliser application. One significant finding was the changed farming system showed a return on investment on the old farming system of minus 10.8% improving to plus 5.9% for the new system. Cane gross margin per hectare on the old system was ñ$148 versus $1157 on the new system. The Loeskow family cannot stress enough the need to continually investigate improved farming practices and invest in new technology and equipment. A preparedness to continually change has been the key to the Loeskow family success.