Heat the olive oil in a large pot over medium heat.
Add the diced onion, carrots, and celery, sautéing until the vegetables are softened and the onions are translucent.
Stir in the minced garlic and diced chicken breast, cooking until the chicken is lightly browned on all sides.
Add the cannellini beans, chicken broth, dried oregano, sea salt, and black pepper to the pot.
Bring the soup to a gentle boil, then reduce the heat and simmer for 15 minutes to allow the flavors to meld.
Stir in the chopped kale and cook for 2-3 minutes until it is wilted and bright green.
Remove from heat and stir in the fresh lemon juice before serving.