In an abandoned wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids, there are various pathways for the leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column of CO2Carbon dioxide to overlying permeable intervals or to the surface (Nygaard and Lavoie, 20102010 - Runar Nygaard, Robert LavoieWell Integrity and Workover Candidates for Existing Wells in the Wabamun Area CO2 Sequestration Project (WASP)see more; Duguid and Tombari, 20072007 - A. Duguid, J. TombariTechnologies for measuring well integrity in a CO2 fieldsee more; Syed and Cutler, 20102010 - Talibuddin Syed, Thor CutlerWell integrity technical and regulatory considerations for CO2 injection wellssee more). These include:
- CO2Carbon dioxide migrationThe movement of fluids in reservoir rocks through the pathways and/or pores of 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 cement (both for cement plugs in the wellboreThe physical hole that makes up 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, it can be cased, open, or a combination of both; open means open for fluid migrationThe movement of fluids in reservoir rocks laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migrationThe movement of fluids in reservoir rocks and for the cement behind the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled, in the production casingA pipe which is inserted to stabilise the borehole of a well after it is drilled/outer casingA pipe which is inserted to stabilise the borehole of a well after it is drilled annuli),
- CO2Carbon dioxide leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column through the annular space between the production casingA pipe which is inserted to stabilise the borehole of a well after it is drilled and the cement behind the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled,
- CO2Carbon dioxide leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column through the annular space between the cement behind the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled and the formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it,
- CO2Carbon dioxide leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column through damaged casingA pipe which is inserted to stabilise the borehole of a well after it is drilled and
- CO2Carbon dioxide leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column through damaged bridge plugs or other mechanical plugging equipment set in the wellboreThe physical hole that makes up 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, it can be cased, open, or a combination of both; open means open for fluid migrationThe movement of fluids in reservoir rocks laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migrationThe movement of fluids in reservoir rocks.
The most common cause of leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column from abandoned wells is failure of the cement to prevent CO2Carbon dioxide flow. This can be either due to failures in the proper application of primary casingA pipe which is inserted to stabilise the borehole of a well after it is drilled cement jobs, cement squeeze jobs and cement plugs or due to cement deterioration when the cement is exposed to both CO2Carbon dioxide and the water acidified by the presence of CO2Carbon dioxide. Although a study on the analysis of the cement in an oil wellManmade hole drilled into the earth to produce liquids or gases, or to allow the injection of fluids with 30 years of CO2Carbon dioxide exposure showed that the cement retained its capacity to prevent any significant flow of CO2Carbon dioxide (Carey et al., 20072007 - J. W. Carey, M. Wigand, S. J. Chipera, G. WoldeGabriel, R. Pawar, P. C. Lichtner, S. C. Wehner, M. A. Raines and G. D. GuthrieAnalysis and performance of oil well cement with 30 years of CO2 exposure from the SACROC Unit, West Texas, USAsee more), various laboratory studies (Carey et al., 20102010 - J. William Carey, R. Svec, R. Grigg, J. Zhang and W. CrowExperimental investigation of wellbore integrity and CO2-brine flow along the casing-cement microannulussee more; Brandvoll et al., 20092009 - Ø. Brandvoll, O. Regnault, I. A. Munz, I. K. Iden and H. JohansenFluid-solid interactions related to subsurface storage of CO2 Experimental tests of well cementsee more) demonstrate the deteriorative effect of CO2Carbon dioxide and CO2Carbon dioxide-brine mixtures on cements. Research has demonstrated that there may be CO2Carbon dioxide leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column even from wells which are properly cemented and abandoned, mainly because of the weak acid formed by the interaction of CO2Carbon dioxide with formation waterWater that occurs naturally within the pores of rock formations which deteriorates the cement quality.
A study performed to investigate the factors affecting 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 leakage(in CO2 storage) The escape of injected fluid from the storage formation to the atmosphere or water column in Alberta, Canada (Watson and Bachu, 20092009 - T.L. Watson, S. BachuEvaluation of the potential for gas and CO2 leakage along wellboressee more), indicates that the factors which have the greatest impact are:
- Geographical location: The study showed that wells at certain regions demonstrated a higher probability of leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column. This may be due to the geological settingThe geological environment, site-specific problems with drilling, completion(well) Refers to the cementing and perforating of casingA pipe which is inserted to stabilise the borehole of a well after it is drilled and stimulation to connect a well bore to reservoir and cementing, and varying operating practices applied by different companies operating in different regions.
- WellboreThe physical hole that makes up 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, it can be cased, open, or a combination of both; open means open for fluid migrationThe movement of fluids in reservoir rocks laterally between the wellbore and surrounding formations; cased means closing of the wellbore to avoid such migrationThe movement of fluids in reservoir rocks deviation: Compared to vertical wells, the occurrence of leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column was higher in deviated wells. The reason may be improper casingA pipe which is inserted to stabilise the borehole of a well after it is drilled cementation in deviated wells due to casingA pipe which is inserted to stabilise the borehole of a well after it is drilled centralisation problems and cement slumping, increasing the probability CO2Carbon dioxide migrationThe movement of fluids in reservoir rocks behind the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled.
- 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 type: Cased wells have higher potential for CO2Carbon dioxide leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column compared to drilled and abandoned wells without casings. The reason can be more stringent abandonment(wells) Actions taken to ensure permanent isolation of the fluids and pressures of exposed permeable zones within 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 from the surface and from lower pressured zones procedures required for drilled and abandoned wells and also, additional pathways for CO2Carbon dioxide migrationThe movement of fluids in reservoir rocks existing in cased and perforated wells.
- Abandonment(wells) Actions taken to ensure permanent isolation of the fluids and pressures of exposed permeable zones within 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 from the surface and from lower pressured zones method: For cased and completed wells, the most commonly used abandonment(wells) Actions taken to ensure permanent isolation of the fluids and pressures of exposed permeable zones within 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 from the surface and from lower pressured zones technique in Alberta is setting bridge plugs capped with cement. The study showed that 10% of these types of abandonment(wells) Actions taken to ensure permanent isolation of the fluids and pressures of exposed permeable zones within 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 from the surface and from lower pressured zones applications will fail in long term (hundreds of years). In comparison, other methods such as setting a cement retainer and squeezing cement through perforations or placing a cement plug across perforations is expected to have a lower failure rate. The damaging effect of CO2Carbon dioxide on the elastomers and metal elements of bridge plugs may also add to the failures of such mechanical plugging equipment.
- Oil price and regulatory changes: As the oil price increases, the driveFluid flow created in formations by pressure differences arising from borehole operations to achieve more with lower cost may have led to lower quality of performed primary cement jobs. Regulatory changes, imposing stricter procedures for 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 abandonment(wells) Actions taken to ensure permanent isolation of the fluids and pressures of exposed permeable zones within 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 from the surface and from lower pressured zones, are expected to improve the abandoned 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.
- Uncemented casingA pipe which is inserted to stabilise the borehole of a well after it is drilled/hole annulus: Low cement tops behind casings were found to be the most important factor for CO2Carbon dioxide leakage(in CO2Carbon dioxide storage) The escape of injected fluid from the storage formationA body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it to the atmosphereThe layer of gases surrounding the earth; the gases are mainly nitrogen (78%) and oxygen (around 21%) or water column in the Alberta study. The absence of cement behind the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled increased the external corrosion of the casingA pipe which is inserted to stabilise the borehole of a well after it is drilled significantly and also allowed the CO2Carbon dioxide to move up the uncemented pathway.