Large scale gas injection test (Lasgit) performed at the Äspö Hard Rock Laboratory: summary report 2007

The deposition hole was closed on the 1st February 2005 signifying the start of the hydration phase. Groundwater inflow through a number of conductive discrete fractures resulted in elevated porewater pressures leading to the formation of conductive channels (piping), the extrusion of bentonite from the hole and the discharge of groundwater to the gallery floor. This problem was addressed by drilling two pressure-relief holes in the surrounding rock mass. Artificial hydration began on the 18th May 2005 after 106 days of testing. Initial attempts to raise porewater pressure in the artificial hydration arrays often resulted in the formation of preferential pathways. These pressure dependent features were not focused in one location but occurred at multiple sites at different times in the test history. These pathways appear to be relatively short lived, closing when water pressure is reduced. It was determined that both pressure relief holes should remain open until the bentonite had generated sufficient swelling pressure to withstand the high water pressure in the system when these holes are closed. Packers were installed into the pressure relief holes on 23rd March 2006 and sections in them closed off over the period to 5th July 2006. There was no repeat of the formation of piping through discrete channels so, on 20th November 2006, pressures to the artificial hydration filters on the canister were increased to 2350 kPa

The HiRES airborne geophysical survey of the Isle of Wight: Logistics Report

This report provides a summary of the logistics of the HiRES airborne geophysical survey conducted in September and October 2008 across the Isle of Wight and part of the Lymington area. The survey was carried out by the Joint Airborne-Geoscience Capability (JAC) established between the Geological Survey of Finland (GTK) and British Geological Survey (BGS). The project is a HiRES survey carried out by the Geophysical Baselines Team under the Environmental Geoscience Baselines Programme. The survey was conducted at high resolution (a flight line spacing of 200 m) and at low altitude (56m) rising to >200 m in the vicinity of conurbations. The three main data sets acquired are magnetic, radiometric (gamma ray spectrometry) and active frequency domain electromagnetic (AEM). The aim of the present report is to provide descriptions of the logistical and in-field processing elements of the survey operations

Update on dilatancy associated with onset of gas flow in Callovo-Oxfordian claystone. Progress report on test SPP_COx-2

This report describes in detail the stress-path permeameter (SPP) apparatus and the on-going second test conducted on Callovo-Oxfordian (COx) claystone from the Bure underground research laboratory (URL) in France. Funding for this study has been provided by the French radioactive waste management operator, Andra, the European Union (FORGE Project, Project number 230357) and the British Geological Survey through its well-founded laboratory programme and the Geosphere Containment project (part of the BGS core strategic programme). The results from test SPP_COx-2 clearly show that at the onset of gas propagation through the test sample dilatancy is observed in three radial and one axial direction. A component of this dilatancy is associated with changes in pore pressure. However, pore-pressure variation cannot account for the full amount of strain recorded and a proportion of the strain observed is the result of gas migration by dilatant pathway formation. The test is on-going and more insight will be achieved once the test is complete

Effect of stress field and mechanical deformation on permeability and fracture self-sealing. Progress report on the Stress Path Permeameter experiment conducted on Callovo-Oxfordian Claystone

This report describes in detail the stress-path permeameter (SPP) apparatus and the first test conducted on Callovo-Oxfordian (CoX) claystone from the Bure underground research laboratory (URL) in France. Funding for this study has been provided by the French radioactive waste management operator, Andra, the European Union (FORGE Project) and the British Geological Survey through its well-founded laboratory programme and the Geosphere Containment project (part of the BGS core strategic programme). The results from the first test conducted using the SPP show that the CoX has a very pronounced time-dependent component of deformation. This has implications for the following tests conducted on CoX as part of the FORGE project, but also has implications when comparing tests on CoX that have been deformed at a much faster rate. Test SPP_CoX-1 was conducted with water as a test permeant at constant pore pressure along a pre-defined stress-path. Volumetric deformation was observed during 16 steps along the stress path, with considerable time-dependent deformation and anisotropy seen in radial strain. The sixteenth stage saw the sample fail through the formation of a fracture after the sample had experienced constant stress conditions for 5.5 days; this emphasises the observed time dependent deformation. Test SPP-CoX-1 will be used to determine the stress-path steps of test SPP-CoX-2. This much more detailed test will follow 5 or 6 steps up to ultimate failure and will include a full hydraulic test, a gas injection test to determine the gas entry pressure, and constant pore-pressure flow tests to examine the changes in permeability along the stress-path. At all times throughout the test radial and axial deformation will be monitored

The High Resolution Airborne Resource and Environmental Survey- (Phase 1) (HiRES-1): background, data processing and dissemination and future prospects

This report provides an overview of the HiRES-1 airborne geophysical survey of Central England. The BGS and World Geoscience (UK) Ltd. carried out the survey jointly in 1998. The three main survey data sets acquired were magnetic, radiometric (gamma ray spectrometry) and Very Low Frequency (VLF) electromagnetic. The main aim of the report is to provide information on the acquisition, processing and storage of the final data and map products produced by the HiRES-1 project. Additional descriptions of ground truthing activities, data licensing and dissemination are also provided. A significant aspect of the project was the assessment of the potential of, and issues raised by, modern, multi-parameter, regional-scale airborne geophysical surveys in the UK context. Some of the main issues outlined in the report are: • The practical difficulties of conducting extensive low level, fixed-wing geophysical surveying in the UK. Issues discussed include CAA regulatory permissions, flight height adjustments above conurbations and surveying near areas with dense air traffic. • The processing challenges introduced by cultural (nongeological) influences on high resolution airborne magnetic data sets in the UK. • The significant amounts of detailed geological and environmental information contained within the radiometric data. • The weak application potential provided by passive (i.e. VLF) measurements, in contrast to active airborne electromagnetic techniques. The future prospects for regional-scale, airborne geophysical surveys in the UK are considered. Such prospects are also influenced by a further set of trial airborne data, obtained in 1999, but not described here. Further detail of the HiRES-1 survey, productivity, technical specifications and data pre-processing are contained in the survey logistics report prepared by WGL: ‘British Geological Survey “Hi-Res Phase One” Airborne Geophysical Survey (Survey Details, Technical Specifications & Processing Summary)’ (WGL 2000)

Trial airborne environmental and geological survey: an initial appraisal of relevance to land-use

A series of four trial airborne environmental and geological surveys was flown by the Geological Survey of Finland (GTK) in collaboration with the British Geological Survey (BGS) in June 1999; the trials were co-sponsored by the Department of the Environment, Transport and the Regions and the Environment Agency. The main objective of these surveys was to test the efficiency of the GTK airborne electromagnetic system in the mapping of potential pollution problems in the UK environment. Gamma spectrometric and magnetometric measurements were also collected to see to what extent these techniques provide complementary information. This report is an initial consideration of the multi-parameter airborne geophysical data in relation to land-use issues. A variety of earth science information for planning and development already exists. The baseline information is reviewed according to scale and resolution. It is noted that the airborne data is of a new type with regard to both information content and spatial continuity. The specific characteristics and advantages of the airborne geophysical data are emphasised. The trial survey data were obtained at high resolution and a large number of anomalous responses have been observed. Since the information is provided at a local-scale a number of issues concerning the nature of the responses observed and the underlying causes have been raised. It will be necessary to improve our understanding of the data before an unambiguous discussion of their specific relevance to land-use issues can proceed. In advance of detailed interpretations of the trial data, the data are presented and discussed in relation to their potential relevance to five land-use issues: (i) Waste planning/Planning and pollution control, (ii) Minerals Planning, (iii) Water supply and water resource protection/Coastal zone management, (iv) Urban regeneration/Peripheral development and new communities and (v) Agriculture and Forestry. It is acknowledged that there are differences between the information needed for planning the use of land, and information which is required for monitoring environmental strategies. The geophysical data appear to have greatest relevance to the latter requirement. Recommendations for ground and subsurface calibration of the data are made

Trial airborne environmental and geological survey of target areas in the English Midlands

A series of four trial airborne environmental and geological surveys was flown by the Geological Survey of Finland (GTK) in collaboration with the British Geological Survey (BGS) in June 1999; the trials were co-sponsored by the Department of the Environment, Transport and the Regions and the Environment Agency. The main objective of these surveys was to test the efficiency of the GTK airborne electromagnetic (EM) system in the mapping of potential pollution problems in the UK environment. Gamma spectrometric and magnetometric measurements were also collected to see to what extent these techniques provide complementary information. The EM data are particularly encouraging and have identified anomalies which may relate to subsurface pollution. The data have identified conductive zones both on the ‘local’ scale (i.e. possibly emanating from domestic landfills) through to regional scale features up to many kilometres in length. The information obtained in relation to spoil tip drainage is of particular note. The data have provided a wealth of information on ‘point source’ anomalies (requiring ground truth information) and diffuse sources that may be connected with groundwater extraction. At two sites (Trent Valley and Langar) the EM technique appears to have met the challenge of detecting conductive targets in a conductive host. Many other features of the data will take time to assess. The radiometric data indicate features of land fill and colliery spoil sites and allow comparison to be made rapidly with the EM data to define the lateral spread of conductive pore fluids beyond the site itself. They can also be used to map site-specific contamination where radioactive elements are present. The radiometric data also give direct indications of solid and drift geology and soil type, providing additional detail to that shown on geological maps (soil maps are not available for much of the UK). The magnetic data have suggested the presence of significant volumes of metallic debris in the Langar landfill sites. This may be significant in terms of the leachates derived and the compaction (through time) of the contrasting fill materials. Compared with the EM and radiometric techniques, the applications of magnetics in environmental studies are rather limited, but such data is worthwhile collecting in view of the marginal additional costs involved

Large scale gas injection test (Lasgit) performed at the Äspö Hard Rock Laboratory. Summary report 2008

This report describes the set-up, operation and observations from the first 1385 days (3.8 years) of the large scale gas injection test (Lasgit) experiment conducted at the Äspö Hard Rock Laboratory. During this time the bentonite buffer has been artificially hydrated and has given new insight into the evolution of the buffer. After 2 years (849 days) of artificial hydration a canister filter was identified to perform a series of hydraulic and gas tests, a period that lasted 268 days. The results from the gas test showed that the full-scale bentonite buffer behaved in a similar way to previous laboratory experiments. This confirms the up-scaling of laboratory observations with the addition of considerable information on the stress responses throughout the deposition hole. During the gas testing stage, the buffer was continued to artificially hydrate. Hydraulic results, from controlled and uncontrolled events, show that the buffer continues to mature and has yet to reach full maturation. Lasgit has yielded high quality data relating to the hydration of the bentonite and the evolution in hydrogeological properties adjacent to the deposition hole. The initial hydraulic and gas injection tests confirm the correct working of all control and data acquisition systems. Lasgit has been in successful operation for in excess of 1385 days

Final Report of FORGE WP4.1.2: verification of critical stress theory applied to repository concepts

This report describes an experimental study of 48 separate experiments examining the validity of critical stress theory. Two main types of experiment were conducted: 1). Loading-unloading tests, where fracture flow was monitored at constant injection pressure as normal load was increased in steps to a given level and then reduced back to the starting stress state; 2). Gas breakthrough experiments, where gas injection pressure was increased in a pressure ramp at constant vertical load. These were conducted with and without active shear. It was found that critical stress theory is valid in predicting the preferential flow of gas in relation to the orientation of the fracture plane with respect to the maximum horizontal stress direction. However, loading unloading experiments showed that understanding the stress history of the rocks is of paramount importance and a mere knowledge of the current stress state is insufficient in accurately predicting the nature of fluid flow. A total of 17 loading-unloading experiments were conducted, all on a 30° slip-plane. The main conclusions of this part of the study were; a). During a loading (vertical stress) and unloading cycle considerable hysteresis in flow was observed signifying the importance of stress history on fracture flow; b). For the case of gas injection the change in flow is chaotic at low normal loads, whereas for water injection the flow reduces smoothly with increased normal load; c). Hysteresis in horizontal stress observed during unloading demonstrates the importance of the ratio between horizontal stress and vertical stress and its control on flow; d). Differences have been observed between injection fluids (water and helium), especially the hysteresis observed in flow. For water injection flow is only partially recovered during unloading, whereas for gas enhanced flow is seen at low normal loads. A total of 26 gas breakthrough experiments were conducted on 0°, 15°, 30°, and 45° discontinuities; both with and without active shear. All tests were conducted in an identical manner. The main conclusions of this part of the study were; a). During gas breakthrough experiments episodic flow/fault valve behaviour was seen with a decrease in subsequent peak pressures and the form of the pressure response was different during subsequent breakthrough events; b). Repeat gas injection testing had shown a consistent gas entry pressure but considerably different, non-repeatable, gas peak pressures; c). Differences in gas entry pressure were seen dependent on the orientation of the fracture; d). Shear can be seen to reduce the gas entry pressure, suggesting that shearing in kaolinite has the opposite effect of self-sealing to gas. Other general observations of gas flow along fractures included; a). The flow of fluids through clay filled fractures is non-uniform and occurs via localised preferential pathways; b). The pressure recorded within the slip-plane showed a negligible fracture pressure and did not vary much in all tests

Final report of FORGE WP4.1.1: the stress-path permeameter experiment conducted on Callovo-Oxfordian Claystone

This report describes in detail the stress-path permeameter (SPP) apparatus and the test programme conducted on Callovo-Oxfordian (COx) Claystone from the Bure underground research laboratory (URL) in France. Funding for this study has been provided by the French radioactive waste management operator, Andra, the European Union (FORGE Project, Project number 230357) and the British Geological Survey through its well-founded laboratory programme and the Geosphere Containment project (part of the BGS core strategic programme). The results from the first test conducted using the SPP showed that COx has a very pronounced time-dependent component of deformation. This had implications for the following test conducted on COx and also has implications when comparing tests that have been deformed at a much faster rate. Test SPP_COx-1 was conducted with water as a test permeant at constant pore-pressure along a pre-defined stress-path. Volumetric deformation was observed during 16 steps along the stress-path, with considerable time-dependent deformation and anisotropy seen in radial strain. The 16th stage saw the sample fail through the formation of a fracture after the sample had experienced constant stress conditions for 5.5 days; this emphasises the observed time dependent deformation. The results from test SPP_COx-2 clearly showed that the sample dilated at the onset of gas propagation; dilatancy was observed in three radial and one axial direction. A component of this volumetric deformation was associated with changes in pore-pressure. However, pore-pressure variation cannot account for the full amount of strain recorded and a proportion of the strain observed was the result of gas migration by dilatant pathway formation. Prior to the sample attaining steady-state flow, outflow from the sample slowly reduced and the conductive features experienced self-sealing. Gas injection pressure was raised and back-pressure was carefully lowered; neither course of action re-initiated flow through the sample