Detection and impacts of leakage from sub-seafloor deep geological carbon dioxide storage

Fossil fuel power generation and other industrial emissions of carbon dioxide are a threat to global climate1, yet many economies will remain reliant on these technologies for several decades2. Carbon dioxide capture and storage (CCS) in deep geological formations provides an effective option to remove these emissions from the climate system3. In many regions storage reservoirs are located offshore4, 5, over a kilometre or more below societally important shelf seas6. Therefore, concerns about the possibility of leakage7, 8 and potential environmental impacts, along with economics, have contributed to delaying development of operational CCS. Here we investigate the detectability and environmental impact of leakage from a controlled sub-seabed release of CO2. We show that the biological impact and footprint of this small leak analogue (<1 tonne CO2 d?1) is confined to a few tens of metres. Migration of CO2 through the shallow seabed is influenced by near-surface sediment structure, and by dissolution and re-precipitation of calcium carbonate naturally present in sediments. Results reported here advance the understanding of environmental sensitivity to leakage and identify appropriate monitoring strategies for full-scale carbon storage operations

Seismic studies of a massive hydraulic fracturing experiment

During a massive hydraulic fracturing experiment carried out at Fenton Hill, New Mexico, 850 microearthquakes, ranging in magnitudes from -3 to 0, were located reliably using arrival times recorded at a set of 5 downhole geophone stations. A subset of these events were located using an upgraded hodogram technique. The seismicity defines a tabular zone with horizontal extent of 900 m, vertical extent of 800 m, and thickness of 150 m. This zone strikes N340/sup 0/E, and dips 75/sup 0/ to the east; its position indicates that no hydraulic connection between the two predrilled wells could be achieved by the fracturing. The distribution of locations obtained from arrival times shows good agreement with those derived from hodograms. Well constrained fault plane solutions were determined for 26 of the larger microearthquakes observed at a surface seismic net. Most solutions display one nearly vertical nodal plane that strikes close to N - S, and a T axis that trends roughly E - W, in agreement with regional indicators of the least principal stress direction. 9 refs., 6 figs

Seismic monitoring of hydraulic fracturing: techniques for determining fluid flow paths and state of stress away from a wellbore

Hydraulic fracturing has gained in popularity in recent years as a way to determine the orientations and magnitudes of tectonic stresses. By augmenting conventional hydraulic fracturing measurements with detection and mapping of the microearthquakes induced by fracturing, we can supplement and idependently confirm information obtained from conventional analysis. Important information obtained from seismic monitoring includes: the state of stress of the rock, orientation and spacing of the major joint sets, and measurements of rock elastic parameters at locations distant from the wellbore. While conventional well logging operations can provide information about several of these parameters, the zone of interrogation is usually limited to the immediate proximity of the borehole. The seismic waveforms of the microearthquakes contain a wealth of information about the rock in regions that are otherwise inaccessible for study. By reliably locating the hypocenters of many microearthquakes, we have inferred the joint patterns in the rock. We observed that microearthquake locations do not define a simple, thin, planar distribution, that the fault plane solutions are consistent with shear slippage, and that spectral analysis indicates that the source dimensions and slip along the faults are small. Hence we believe that the microearthquakes result from slip along preexisting joints, and not from tensile extension at the tip of the fracture. Orientations of the principal stresses can be estimated by using fault plane solutions of the larger microearthquakes. By using a joint earthquake location scheme, and/or calibrations with downhole detonators, rock velocities and heterogeneities thereof can be investigated in rock volumes that are far enough from the borehole to be representative of intrincis rock properties

Clinical and genetic analyses in a patient with PAPA syndrome complicated with inflammatory bowel disease

POSTER PRESENTATIO

Multicore Scheduling for Lightweight Communicating Processes

Process-oriented programming is a design methodology in which software applications are constructed from communicating concurrent processes. A process-oriented design is typically composed of a large number of small isolated concurrent components. These components allow for the scalable parallel execution of the resulting application on both shared-memory and distributed-memory architectures. In this paper we present a runtime designed to support process-oriented programming by providing lightweight processes and communication primitives. Our run-time scheduler, implemented using lock-free algorithms, automatically executes concurrent components in parallel on multicore systems. Run-time heuristics dynamically group processes into cache-affine work units based on communication patterns. Work units are then distributed via wait-free work-stealing. Initial performance analysis shows that, using the algorithms presented in this paper, process-oriented software can execute with an efficiency approaching that of optimised sequential and coarse-grain threaded designs