By approaching to the last production stages of reservoirs in the Danish North Sea, reliable clogging of production and injection wells becomes more important. How can we make sure that an abandoned well is properly sealed so that there will be no environmental concern regarding hydrocarbon leakage 100 years from now?
There are several potential approaches for the safe plugging of wells and formations, and the injection of bacteria is one of them. Yes, it is a little hard to believe that these tiny microorganisms can help us to plug a high-pressure formation, but it seems that have a role to play. An important section of my research is to find out which bacterial species are willing to work alongside us to avoid potential pollution of the environment!
The objective of this study is to considerably reduce the permeability of porous media by inducing the precipitation of carbonate minerals. This approach relies on creation of an aqueous system that is supersaturated with carbonate and calcium ions, which will be followed by calcite precipitation. By establishing a high pH environment, the carbonate equilibria will be moved toward the ionization of carbonic acid/bicarbonate and release of carbonate ions. Adding calcium ion to this system will simply result in calcite precipitation.
There are different microbial species (e.g., ureolytic bacteria and nitrate-reducing microorganisms) that contribute to creation of a high pH system. That’s why it is being called microbially induced calcite precipitation (MICP). MICP has applications in different fields of studies such as water remediation and selfhealing cement; however, the absence of oxygen is not usually a big concern in such fields. Therefore, anaerobic MICP process (reservoir condition) has not been thoroughly investigated. Moreover, for reliable sealing of an abandoned formation, it is favorable to have stable precipitates that create and maintain a zero-permeability media, which is not thoroughly studied.
In this PhD program, the applicability as well as the efficiency of various methods for controlled clogging of porous media will be evaluated, so that we can answer the following questions:
1. How efficient and fast are these methods at the pore scale and well-scale?
2. What are the optimum conditions for the idea to work?
3. Would the produced minerals stay as a solid material and seal the formation forever?