Andrew Duguid

Leakage of CO 2 Through Abandoned Wells: Role of Corrosion of Cement

The potential leakage of CO 2 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 for North American basins, shows that a CO 2 plume and/or acidified brine may encounter up to several hundred wells. If carbon dioxide is geologically stored in regions, such as this, that have experienced intensive exploration for petroleum products, the acidified brine will come into contact with numerous abandoned wells. Corrosion of the cement that seals the well could lead to rapid leakage, so it is essential to determine the duration and intensity of exposure to the acid. Detailed numerical simulations with Dynaflow, incorporating a flash calculation to find the phase distribution and speciation in the brine, indicate that the carbonated brine may spend years in contact with the cement in abandoned wells. Preliminary results from an ongoing experimental study of cement corrosion indicate that the rate of attack is rapid, when the pH of the solution is low, so the risk of leakage will be high if the acidic brine can flow through an annulus and bring fresh acid into contact with the cement.

Chapter 10 – Leakage of CO2 Through Abandoned Wells: Role of Corrosion of Cement

The potential leakage of CO 2 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 for North American basins, shows that a CO 2 plume and/or acidified brine may encounter up to several hundred wells. If carbon dioxide is geologically stored in regions, such as this, that have experienced intensive exploration for petroleum products, the acidified brine will come into contact with numerous abandoned wells. Corrosion of the cement that seals the well could lead to rapid leakage, so it is essential to determine the duration and intensity of exposure to the acid. Detailed numerical simulations with Dynaflow, incorporating a flash calculation to find the phase distribution and speciation in the brine, indicate that the carbonated brine may spend years in contact with the cement in abandoned wells. Preliminary results from an ongoing experimental study of cement corrosion indicate that the rate of attack is rapid, when the pH of the solution is low, so the risk of leakage will be high if the acidic brine can flow through an annulus and bring fresh acid into contact with the cement.

Tracer transport test in simple fractured media

Scientific visualization is an important method for understanding complex hydrologic processes. A series of experiments was conducted using two-dimensional fracture networks built of transparent plexiglass blocks as a new approach to process visualization. A digital monitoring method was used to visualize transport of a tracer in the fracture networks. The approach for visualizing tracer transport in fractured networks provided both quantitative and quantitative data. From the experiments conducted it was found that tracer spreading in fractured media was complex even in simple networks consisting of equally spaced finite fractures. The combined effects of fracture orientation and aperture variability resulted in the complex tracer spreading.

Leakage of CO2 Through Abandoned Wells

The potential leakage of CO 2 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 for North American basins, shows that a CO 2 plume and/or acidified brine may encounter up to several hundred wells. If carbon dioxide is geologically stored in regions, such as this, that have experienced intensive exploration for petroleum products, the acidified brine will come into contact with numerous abandoned wells. Corrosion of the cement that seals the well could lead to rapid leakage, so it is essential to determine the duration and intensity of exposure to the acid. Detailed numerical simulations with Dynaflow, incorporating a flash calculation to find the phase distribution and speciation in the brine, indicate that the carbonated brine may spend years in contact with the cement in abandoned wells. Preliminary results from an ongoing experimental study of cement corrosion indicate that the rate of attack is rapid, when the pH of the solution is low, so the risk of leakage will be high if the acidic brine can flow through an annulus and bring fresh acid into contact with the cement.

The effect of CO2 sequestration on oll well cements

Publisher Summary Depleted oil- and gas-bearing formations represent likely locations for the disposal of CO2. Oil-and gas-bearing formations have proved capable of trapping fluids over geologic times. Because of the removal of hydrocarbons from these formations via wells, a potential avenue for leakage has been created. Cements are used in the construction (primary cement) and abandonment (plug cement) of oil and gas wells. Because wells represent a potential leakage pathway, it is important to study the effects of sequestration on the integrity of materials used to make them. Experiments are conducted to examine the effects of CO2 sequestration conditions on cements used to construct and abandon oil and gas wells. The experimental conditions consist of two influent pH 2.4 and 3.7, and two temperatures, 23° and 50°C, are considered likely for potential sequestration formations. The results show that significant damage, including complete loss of the calcium hydroxide phase, can take place over a time span as short as seven days.