Obviously hydrocarbon storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere operations can be labelled as a more mature technology, with experiences dating back for almost a century (Perry, 2004). At least in case of the US and the EUEuropean Union, monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions of hydrocarbon storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere uses a number of quite similar monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions approaches and methods as proposed for CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere. These include PVT inventory verification(CO2 storage) The proof, to a standard still to be decided, of the CO2 storage using monitoring results; (in the context of CDM) The independent review by a designated operational entity of monitored reductions in anthropogenic emissions, surface and deep wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions (and reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids testing), gas sampling and tracing and last but not the least, caprockRock of very low permeability that acts as an upper seal to prevent fluid flow out of a reservoir integrity evaluation. In case of natural gasGas stored underground; It consists largely of methane, but can also contain other hydrocarbons, water, hydrogen sulphide and carbon dioxide, these other substances are separated before the methane is put into a pipeline or tanker storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions (wells penetrating the reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it and potable aquifers) seems to be the most important monitoringMeasurement and surveillance activities necessary for ensuring safe and reliable operation of a CGS project (storage integrity), and for estimating emission reductions method for leak detection (Perry, 2004).