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Gas Well Productivity Loss

Jagannathan MahadevanPetroleum Engineering, University of Tulsa, Tulsa, OK
Jagannathan Mahadevan

Productivity Loss in Unconventional Natural Gas Wells Due to Salt Crystallization

Jagannathan MahadevanPetroleum Engineering, University of Tulsa, Tulsa, OK

“The Petroleum Research Fund was my first successful sponsor, and the grant allowed me to conduct the research that I like the most,” states Dr. Mahadevan. “Because there are not a lot of strings attached to the funding, it supports novel and creative approaches, and gives the grantee a lot of flexibility in how he or she brings the research forward.”

Members of the research team Members of the research team including (from left to right) Gaurav Seth, Dinesh Dabholkar, Jagannathan Mahadevan, Hai Hoang, Ying Li, Jamie Sampayo, and Alfredo sampayo.

Dr. Mahadevan’s curiosity has led him to investigate natural gas recovery from unconventional onshore resources. “I started as a chemical engineer in an academic setting, which brought me to chemical and natural gas processing plants,” says Dr. Mahadevan. “I was very keen on working on energy, especially natural gas, since natural gas is one of the largest and cleanest energy resources we have right now. After a brief exposure to natural gas production facilities I was curious to learn about the source of natural gas which led me to explore subsurface engineering.”

Most of the research in natural gas recovery has focused on conventional resources–existing reservoirs that allow for relatively easy gas extraction. Dr. Mahadevan and his team study how to recover gas locked away in very tight conditions or states of low permeability such as tight gas sandstone or shale gas. In particular, the scientists have focused on the pore scale phenomena affecting natural gas flow such as crystallization of salt and its impact on the productivity of natural gas reservoirs. Generally, natural gas occurs along with brine which is generally high in dissolved salt content. When gas is produced, brine evaporates due to gas expansion resulting in super saturation and subsequent crystallization. Capillary effects can be important as liquid migrates due to capillary effects, bringing more salt that may even plug the well completely. Thanks to his research, Dr. Mahadevan has created a model that helps predict permeability and porosity in the cases in which salt crystallization occurs. “We now know exactly how to predict when the salt deposition will be important, and once we have this condition, we can treat the wellbore with chemicals so that the migration due to capillary effects stops,” according to Dr. Mahadevan.

In the work that has just concluded, Dr. Mahadevan focused on tight gas, but moving forward, he hopes to explore the effects of salt crystallization on shale gas recovery as well. “The problem with offshore deposits of oil is that they are very hard to recover. One has to go to great water depth, which leads to environments that can’t easily be controlled if an accident occurs. The work that I am doing will help produce clean, natural gas from onshore resources,” indicates Dr. Mahadevan. “Natural gas burns much cleaner than other resources and can be a very good bridge fuel to alternative energy resources such as wind and solar power, helping us transition into a cleaner energy strategy.”

“Although the PRF funds were much less than those from other projects I had, they enabled me to produce the most research,” Dr. Mahadevan says with pride. His research has resulted in one published paper with another in the works, supported two undergraduate research scholars who later went on to do graduate studies, and has been integrated into the course he currently teaches titled “Transport in Porous Media”.