Bibliography - A. Duguid

1. Scherer, George, B. Kutchko, N. Thaulow, A. Duguid, and Bryant Mook, 2011: Characterization of cement from a well at Teapot Dome Oil Field: Implications for geological sequestration. International Journal of Greenhouse Gas Control, Elsevier, (5), doi:10.1016/j.ijggc.2010.06.010 115-124
   [ Abstract ]

   Wellbores represent the weakest link in terms of CO₂ storage permanence. As a result, special attention to the numerous existing wells that perforate storage formations is needed. The pre-injection condition of the cement can influence the rate (and type) of alteration by the injected CO₂ plume. The condition of the existing well cement depends on a variety of factors including wellbore/formation and wellbore/brine interactions as well as the composition and type of cement placed in the well (i.e. type of admixtures used, water/solids ratio, sulfate resistant mixes, etc.). In this paper, the details of recovering wellbore cement from an older well to determine pre-injection seal integrity are described. Petrographical and chemical analyses are presented for samples of cement that were retrieved from a 19-year-old well at Teapot Dome in Wyoming. Examination revealed that the retrieved cement had altered as a result of original slurry composition and with respect to the local downhole wellbore environment. Although samples were obtained from a single well, significant differences were observed in their alteration and condition. Sulfate attack resulted in abundant ettringite formation in a cement sample taken adjacent to the Wall Creek sandstone (3060 ft), while cement taken adjacent to the Tensleep formation (5478 ft) was decalcified and enriched in magnesium, owing to reaction of calcium hydroxide in the cement with the dolomitic formation.

2. Duguid, A., and George Scherer, 2010: Degradation of oilwell cement due to exposure to carbonated brine. International Journal of Greenhouse Gas Control, 4, doi:10.1016/j.ijggc.2009.11.001 546–560
   [ Abstract ]

   The growing interest in geologic carbon sequestration has highlighted the need for more data on how well cements react to CO₂ exposure. This paper describes a series of experiments that was conducted to examine the effects of flowing carbonated brine on well cements. Class H cement pastes were exposed to the ranges of temperature (20–50 °C) and pH (2.4–5) characteristic of geosequestration conditions at a depth of about 1 km. The exposed cements and the reactor effluents were analyzed using multiple techniques including optical microscopy, X-ray diffraction, EPMA, and ICP-OES. The results showed that if the solution was pre-equilibrated with calcium carbonate, as would be expected in a limestone formation, there was no detectable attack. However, under the pH and temperature conditions to be expected in a sandstone formation, the initial rate of attack was on the order of millimeters per month. The outer layers of the cements reacted under sandstone-like conditions were fully degraded based on the results of the XRD and EPMA analyses. Inside the degraded layers there was a calcium carbonate-rich layer, a layer depleted of calcium hydroxide, and an unreacted cement core. The rate of degradation of the cement in these experiments was controlled by the rate of dissolution of the calcium carbonate-rich layer, after its formation, and diffusion through the fully degraded layers.

3. Duguid, A., M. Radonjic, and George Scherer, 2007: The Effect of Carbonated Brine on Well Cement Used in Geologic Formations. Proceedings of the 12th ICCC, eds. J.J. Beaudoin, J.M. Makar, L. Raki (Canada), paper TH4-10.2,
   [ Abstract ]

   Carbon sequestration in abandoned petroleum fields may be a short-term solution to reducing anthropogenic emissions of CO₂. If sequestration is adopted on a large scale, it will be important to understand how CO₂ may leak out of sequestration formations via abandoned wells. Within an abandoned petroleum well there are multiple pathways that CO₂ may use to escape to the atmosphere. These include leakage through the cement that makes up the primary and/or plug cement in the well, leakage through the interface between the primary cement and the geologic formation, and leakage through the interface between the well cement and the well casing. As the plume of carbonic acid created by sequestration reaches an abandoned well, the first potential pathway with which it come in contact is the interface between the geologic formation and the primary well cement. In order to better understand what takes place when carbonic acid reaches the cement-rock interface, a series of batch experiments was conducted. This paper describes experiments that were conducted on composite samples that were made from Class H well cement and Salem limestone or Berea sandstone.

4. Duguid, A., 2006: The Effect of Carbonic Acid on Well Cements. Ph.D. thesis for Civil and Environmental Engineering, Princeton University, http://proquest.umi.com/pqdlink?Ver=1&Exp=09-27-2014&FMT=7&DID=1192184611&RQT=309&attempt=1&,
   [ Abstract ]

   Sequestration in abandoned petroleum fields has the potential to reduce atmospheric emissions of CO₂ if adopted on a large scale. When CO₂ comes in contact with brine in the sequestration formation, it will form carbonic acid. The acid may damage cement that is used to construct and abandon wells in the sequestration formation, allowing the wells to leak. CO₂ release from a sequestration formation through abandoned wells to the vadose zone and then from the vadose zone into a residence could cause exposure to high levels of CO₂. This study presents the results of two types of experiments that were conducted in order to understand how CO₂ will affect well cements. This dissertation also presents a hypothetical risk assessment that examines the risks that a sequestration site may pose. The experiments examine how well cements react when exposed to carbonated brines at 20° and 50°C. Month-long flow-through experiments were conducted on samples made from Class H neat paste and Class H cement containing 6% bentonite under conditions that simulated sandstone (pH 2.4 and 3.7) and limestone (pH 5) sequestration formations. Year-long batch experiments were conducted on composite samples made from Class H well cement and either sandstone or limestone in order to determine how carbonated brine affects the cement-stone interface. The results of the flow-through experiments showed that calcium-containing phases in cement may be completely degraded and the formation of the calcium carbonate layer acts to slow, but not stop, degradation. The results of the batch experiments showed that carbonated brines can degrade cement and damage the integrity of the cement-stone interface. The damage to the cement at the cement-stone interface caused an order-of-magnitude increase in permeability in the sandstone-cement samples. The risk assessment identifies two potential screening levels. The assessment then uses a semianalytical wellfield model coupled with analytical models of diffusion through the vadose zone and foundation walls to establish CO₂ concentrations in residential basements. The results show CO₂ levels may not reach either screening level unless the value of the air-exchange rate in the houses is small.

5. Duguid, A., and Michael Celia, May 2006: Geologic CO₂ sequestration in abandoned oil and gas fields and human health risk assessment. Proceedings of the 5th Annual Conference on Carbon Capture and Sequestration,
   [ Abstract ]

   Sequestration in abandoned petroleum fields has the potential to reduce atmospheric emissions of CO₂ if it is adopted on a large scale. However, sequestration sites may pose risks to people who live in their vicinity. CO₂ release from the sequestration formation through abandoned wells to the vadose zone and then from the vadose zone into people’s houses could cause exposure to high levels of CO₂. CO₂ is different from many other chemicals that may be released into the environment because its effects are acute instead of chronic. Existing literature on the health effects of CO₂ in humans was surveyed to establish risk-based screening levels that could be used near a sequestration site. Two potential screening levels were identified: (1) one person in a million becomes dizzy from inhalation of CO₂ in the basement of a house (3.7780% CO₂), and (2) one person in a million loses consciousness from exposure to CO₂ (6.6744% CO₂). A hypothetical risk assessment was conducted using a semianalytical wellfield model developed at Princeton University coupled with analytical models of diffusion through the vadose zone and foundation walls. The assessment assumed that a wellfield in Alberta, Canada, was transformed into a sequestration site with an injection rate of 43,200 t-CO₂/day and that a subdivision has been built near the site. The results showed that CO₂ levels on the site will not reach either of the identified screening levels unless the value used for the exchange rate for air in the houses is very small.

6. Duguid, A., M. Radonjic, and George Scherer, June 2006: The effect of carbonated brine on the interface between well cement and geologic formations under diffusion controlled conditions. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8),
   [ Abstract ]

   A series of experiments was conducted on composite samples made from Class H well cement and either sandstone or limestone in order to determine the effect on the cement-stone interface in a petroleum well from exposure to carbonated brine. The experiments were carried out over the course of a year and showed that carbonated brines can degrade cement at the cement-stone interface.

7. Duguid, A., M. Radonjic, and George Scherer, 2005: Degradation of well cements exposed to carbonated brine. Proceedings of the 4th Annual Conference on Carbon Capture and Sequestration, http://www.netl.doe.gov/publications/proceedings/05/carbon-seq/Tech%20Session%20Paper%20186.pd,
   [ Abstract ]

   With increased attention on how people affect the climate, interest has grown in the anthropogenic emissions of greenhouse gases such as carbon dioxide. Subsurface carbon sequestration in abandoned petroleum fields may represent a chance to reduce CO₂ emissions. In order to understand how CO₂ may escape from the storage formation back to the atmosphere through abandoned wells, a set of four experiments was conducted. The experiments looked at how well cements reacted to carbonated brines at 20° and 50°C at pH 2.4 and 3.7. The results showed severe degradation to samples made from Class H well cement. The degradation occurred over the course of 31 days.

8. Duguid, A., M. Radonjic, and George Scherer, April 2005: Durability of well cements: corrosion by carbonic acid. Proceedings of the 107th Annual Meeting of the American Ceramics Society,
   [ Abstract ]

   With an increased focus on how people affect the climate, interest has grown in the anthropogenic emissions of greenhouse gases such as carbon dioxide. Subsurface carbon sequestration in abandoned petroleum fields may represent a chance to reduce CO₂ emissions. In order to understand how CO₂ may escape from the storage formation back to the atmosphere through abandoned wells, a set of four experiments was conducted. The experiments looked at how well cements reacted to carbonated brines at 20° and 50°C at pH 2.4 and 3.7. The results showed severe degradation to samples made from Class H well cement, the degradation occurring over the course of 31 days.

9. Scherer, George, Michael Celia, Jean Hervé Prévost, , R. Bruant, A. Duguid, R. Fuller, S. Gasda, M. Radonjic, and W. Vichit-Vadakan, 2005: Leakage of CO₂ through Abandoned Wells: Role of Corrosion of Cement. The CO₂ Capture and Storage Project (CCP), Volume II, Chapter 10, 823-844
   [ Abstract ]

   The potential leakage of CO₂ from a geological storage site through existing wells represents a major concern. An analysis of well distribution in the Viking Formation in the Alberta basin, a mature sedimentary basin representative of North American basins, shows that a CO₂ plume and/or acidified brine may encounter up to several hundred wells. A review of the literature indicates that cement is not resistant to attack by acid, but little work has been reported for temperatures and pressures comparable to storage conditions. Therefore, an experimental program has been undertaken to determine the rate of corrosion and the changes in properties of oil well cements exposed to carbonated brine. Preliminary results indicate a very high rate of attack, so it is essential to have accurate models of the composition and pH of the brine, and the time that it will remain in contact with cement in abandoned wells. A model has been developed that incorporates a flash calculation of the phase distribution, along with analysis of the fluxes and pressure of the liquid, solid and vapor phases. A sample calculation indicates that wells surrounding the injection site may be in contact with the acidified brine for years.

10. Duguid, A., M. Radonjic, R. Bruant, T. Mandecki, George Scherer, and Michael Celia, 2004: The Effect of CO₂ Sequestration on Oil Well Cements. Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies, (GHGT-7), http://www.princeton.edu/~cmi/research/Vancouver04/GHGT7Duguid.pdf,
    [ Abstract ]

    Experiments were conducted to examine the effects of CO₂ sequestration conditions on cements used to construct and abandon oil and gas wells. The results showed that significant damage, complete loss of the calcium hydroxide phase, can take place over a time span as short as seven days.

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