According to the EU CCS DirectiveDirective 2009/31/EC of the European Parliament and of the Council of 23 April 2009 on the geological storage of carbon dioxide, the main objectives/purposes of monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions are to: i) assess whether the injected CO2Carbon dioxide, including CO2 plumeDispersing volume of CO2-rich phase contained in target formation, is behaving as expected, ii) identify if any migrationThe movement of fluids in reservoir rocks, leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column or significant irregularities occur and iii) assess whether any identified leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column is damaging the environment or human health.
Three categories of monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions can be identified according to the Guidance Document 2 (2011):
- Mandatory monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions (for all sites). This includes the parameters (injectionThe process of using pressure to force fluids down wells rate, pressure, temperature, gas composition) described in Section 3.2.2 that are important for the operational monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions. These parameters are typically measured by downhole instrumentation or at the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injectionThe process of using pressure to force fluids down wells of fluids head and are required to be monitored continuously or intermittent during the injectionThe process of using pressure to force fluids down wells phase. Downhole pressure and temperature measurements as wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injectionThe process of using pressure to force fluids down wells of fluids as measurements at the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injectionThe process of using pressure to force fluids down wells of fluids head are also recommended during the post injectionThe process of using pressure to force fluids down wells period.
- Required (site-specific) monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions. The objective of this monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions is to demonstrate the integrity of the sealAn impermeable rock that forms a barrier above and around a reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids such that fluids are held in the reservoirA subsurface body of rock with sufficient porosityMeasure for the amount of pore spaceSpace between rock or sediment grains that can contain fluids in a rock and permeabilityAbility to flow or transmit fluids through a porous solid such as rock to store and transmit fluids, fault(geology) A surface at which strata are no longer continuous, but are found displaced and wells at the specific site. This monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions will be closely linked with the site-specific riskConcept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event. To assess fault(geology) A surface at which strata are no longer continuous, but are found displaced integrity repeated 3D seismic surveys and pressure interference can be employed. The operator is required to perform monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions with a frequency that gives sufficient input to dynamic modelling. The optimal schedule for seismic surveys is site-specific and depends on the model parameters, dominant 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 mechanism, target depth, caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir and overburdenRocks and sediments above any particular stratum etc. The wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injectionThe process of using pressure to force fluids down wells of fluids integrity (annular pressure, wireline logging, optical wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injectionThe process of using pressure to force fluids down wells of fluids logging, cement bond logging, soil gas measurements) needs to be measured in the order of months during the injectionThe process of using pressure to force fluids down wells phase.
- Optional contingency monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions (site-specific). The third category refers to a contingency monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions system which will be used in the event of irregularities. Contingency monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions needs to be considered and planned for at an early stage in the project and should be based on the site-specific riskConcept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event analysis. For example, microseismic monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions (geophones behind casingA pipe which is inserted to stabilise the borehole of a well after it is drilled of a wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injectionThe process of using pressure to force fluids down wells of fluids) can be a useful method for contingency monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions during the injectionThe process of using pressure to force fluids down wells phase.
Different phases of the project require different frequency of monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions (cf. Chapter 1). The monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions frequency during baseline survey and baseline data collection in the pre-injectionThe process of using pressure to force fluids down wells phase will typically be same as or higher than during the operational phase. In the event of an irregularity, higher frequencies of monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions and possibly additional monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions tools will be required.