Shallow 2D Seismic methods implement the principles of subsurface imaging from reflected seismic waves. Seismic reflection technology has been applied to characterising the shallow geology at locations that are environmentally contaminated and in detecting shallow subsurface voids that might be related to sinkholes, tunnels, or construction, in mapping faults or bedrock surfaces and in other situations. Shallow seismic might be deployed in time-lapse mode to look for changes from the baseline, or post-injectionThe process of using pressure to force fluids down wells when a leak is suspected to try to image a concentration of trapped gas phase CO2Carbon dioxide by mapping a bright spot. This technology can provide high-resolution images of the subsurface for monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions. Should CO2Carbon dioxide leak and accumulate at shallow depth, the low density of the gas phase would be expected to produce an area of significantly lower velocity, readily mapped as change from baseline, or even in a single survey, as a bright spot.
Seismic techniques respond to a significant change in velocity of sound through the rock/fluid system, so that CO2Carbon dioxide dissolved in groundwater would not likely produce a measurable signal. Thin or low-saturation gas phase CO2Carbon dioxide (near wells or faults) may also produce signal below the resolution sensitivity and, therefore, undetectable. Resolution of sound waves and depth of penetration are inversely related; cost of surveys and processing and the sourceAny process, activity or mechanism that releases a greenhouse gasGas in the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) that absorbs and emits infrared radiation emitted by the Earth’s surface, the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%), and clouds; thus, trapping heat within the surface-troposphere system. e.g. water vapour (H2O), carbon dioxide (CO2Carbon dioxide), nitrous oxide (N2O), methane (CH4), ozone (O3), sulfur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs), an aerosol, or a precursor thereof into the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) and receiver spacing are also related, requiring careful design. Static errors caused by changes in shot points or in near surface conditions can reduce detection; they may also add noise. It is not possible to quantify the amount of CO2Carbon dioxide using seismic methods, as occupied formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it thickness and saturation are both difficult to quantify. Mass-balance and dissolution/mineral trapping(CO2Carbon dioxide) ContainmentRestriction of the movement of a fluid to a designated volume (e.g. reservoir) or immobilisation of CO2Carbon dioxide, there are four main trapping mechanisms: structural or stratigraphicThe order and relative position of geological strata trapping; residual CO2Carbon dioxide trapping (capillary trappingImmobilisation of a fraction of in-situ fluids by capillary forces) by capillary forces; solubility trappingA process in which fluids are retained by dissolution in liquids naturally present by dissolution of CO2Carbon dioxide in resident formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it fluids forming a non-buoyant fluid; and mineral trapping where CO2Carbon dioxide is absorbed by solid minerals present in the storage(CO2Carbon dioxide) A process for retaining captured CO2Carbon dioxide, so that it does not reach the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) volume are difficult to monitor. It is noted that only migrationThe movement of fluids in reservoir rocks in the acquisition direction can be followed, whereas migrationThe movement of fluids in reservoir rocks in any other direction cannot be quantified directly.