CO2Carbon dioxide leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column from the storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere reservoirA subsurface body of rock with sufficient porosity and permeability to store and transmit fluids through operating and especially orphaned, abandoned and even old wells is considered to be a potential leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column pathway for a CCSCarbon dioxide Capture and Storage project, which is worth considering carefully (Ide et al.,2006). The possible reasons why a wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids may be leaking are (Kuuskra and Godec, 2007):
- The wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids was poorly designed or completed, allowing gas migrationThe movement of fluids in reservoir rocks along the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids or wellboreThe physical hole that makes up the well, it can be cased, open, or a combination of both; open means open for fluid migration laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migration;
- An unanticipated wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids failure occurred (such as parted casingA pipe which is inserted to stabilise the borehole of a well after it is drilled);
- When abandoned, the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids was inadequately plugged and sealed.
In contrast to the natural geological system, the wellboreThe physical hole that makes up the well, it can be cased, open, or a combination of both; open means open for fluid migration laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migration system is an engineering structure(geology) Geological feature produced by the deformation of the Earth’s crust, such as a fold or a fault; a feature within a rock such as a fracture; or, more generally, the spatial arrangement of rocks. A general downhole wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids configuration consists of multiple casings, usually made of steel. In many cases the annular space between geological formationA lithostratigraphic subdivision within a sedimentary succession within which distinct rock layers can be found and mapped and the steel casingA pipe which is inserted to stabilise the borehole of a well after it is drilled is (partly) filled with cement. InjectionThe process of using pressure to force fluids down wells or production wells often are equipped with injectionThe process of using pressure to force fluids down wells or production tubing. Abandoned wells will be sealed with several cement and potentially mechanical plugs (Guidance Document 2, ECEuropean Commission, 2011b).
Wells drilled for the purpose of CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere operations can be designed, completed and abandoned according to requirements applicable to long-term containmentRestriction of the movement of a fluid to a designated volume (e.g. reservoir). Even previously drilled wells, configured without taking into account future CO2Carbon dioxide storage(CO2) A process for retaining captured CO2, so that it does not reach the atmosphere purposes, can often be modified to comply with requirements. The main problem lies with already abandoned wells that are no longer accessible. WellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids flaws leading to leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column through or along the wellboreThe physical hole that makes up the well, it can be cased, open, or a combination of both; open means open for fluid migration laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migration is nothing new. The oil and gas industry has decades of experience and offers standard techniques as wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids as advanced technologies to repair leaks in the various parts of a wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids. If required, injectionThe process of using pressure to force fluids down wells tubing and packers can be replaced, leaking casingA pipe which is inserted to stabilise the borehole of a well after it is drilled can be repaired, or cement can be squeezed behind the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled. In the case of a blow-out(well) Refers to catastrophic failure of a well when the petroleum fluids or water flow unrestricted to the surface, standard oil and gas industry techniques are available to 'kill' a wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids (e.g. injecting heavy mud/weighted brine into the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled). A good overview of wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids remediation measures is provided by Meyer (2007).
In case of leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column of injectionThe process of using pressure to force fluids down wells tubing, first of all the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids must be "killed". After killing the wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids e.g. by injecting heavy mud or weighted brine into the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled, the failed tubing string needs to be pulled out of the hole. At the surface the tubing can be hydrotested, after which the leaking tubing joint can be replaced. In case no leaks are detected, failure may have occurred in a tubing collar which was remedied as the tubing was rerun.
Leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column of casingA pipe which is inserted to stabilise the borehole of a well after it is drilled is usually caused by a damage to casingA pipe which is inserted to stabilise the borehole of a well after it is drilled steel due to, e.g, mechanical erosion or chemical degradation. There are many measures available to repair such damage (Meyer, 2007):
- A squeeze job, forcing cement or a chemical sealant through leaks or intentional perforations into specified locations of the annulus, may prevent communication between the inside casingA pipe which is inserted to stabilise the borehole of a well after it is drilled and casingA pipe which is inserted to stabilise the borehole of a well after it is drilled-formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it or casingA pipe which is inserted to stabilise the borehole of a well after it is drilled-casingA pipe which is inserted to stabilise the borehole of a well after it is drilled annuli.
- Alternatively, a new liner (either fiberglass or steel) can be placed over the leaking section, effectively covering the leak.
- A special application of the latter involves the use of expandable tubulars. This technology enables expansion of the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled or liner by up to 20% in diameter after being run down-hole. For this purpose, an expansion tool that exceeds the inner diameter of the tube by the required amount of expansion is forced through the pipe.
In case of leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column behind the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled due to lacking or inadequate cement sheath, several methods can be applied to remediate the cement sheath and achieve isolation (Arts et al., 20092009 - R. Arts, van den Belt F., Benedictus T., Blom M., A. de Buck, H. Croezen, C. Hofstee, Ch. Kolesar, T. Koryl, M. Lewitt, M. Nepveu, H. Stoiber, S. Wartmann, T. WildenborgSupport to the Introduction of the Enabling Legal Framework on Carbon Dioxide Capture and Storage (CCS)see more):
- Squeeze cementing involves the process of forcing by pressure cement slurry into a specified location in a wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids through perforations in the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled or liner. Once the slurry encounters a permeable formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it, the cement solids are filtered out of the slurry as the liquid phase is forced into the formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it matrix in the form of cement filtrate. Squeeze cementing is a remedial cementing technique used to repair flaws in primary cement or damage incurred by corrosive fluids. A properly designed squeeze-cement operation will fill the relevant holes and voids with cement filter cake that will cure to form an impermeable barrier. Also chemical sealants are available for squeeze jobs.
- Block cementing is used to isolate a permeable zone. To this purpose the sections above and below the target formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it are perforated and squeezed.
- A circulating squeeze involves circulating cement between two sets of perforations, isolated in the string by a packer or cement retainer. The operations consist of an initial circulation with water or acid as receding fluid, a subsequent circulation of the interval with a cleaning wash fluid, and pumping and displacing of the cement slurry. This method is a low pressure squeeze. Except for some increase in hydrostaticPertaining to the properties of a stationary body of water pressure resulting from the increasing cement column in the annulus, no pressure build-up is associated with this type of cement squeeze. The exact amount of required cement is unknown, leading to the use of excess cement. This holds the riskConcept that denotes the product of the probability of a hazard and the subsequent consequence of the associated event that cement slurry enters the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled above the packer or retainer. If this cement would cure, the tubing may become stuck in the hole.
- Alternatively, expandable tubulars could be applied on the outside of the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled.
Leaking injectionThe process of using pressure to force fluids down wells and observation wells where repair is impossible should be plugged and abandoned. The same goes for leaking old abandoned wells that need to be re-plugged. Procedures of wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids abandonment(wells) Actions taken to ensure permanent isolation of the fluids and pressures of exposed permeable zones within a well from the surface and from lower pressured zones are wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids-known from the oil and gas industry (Randhol et al., 2007).