Generously coat the bottom of a large pot or Dutch oven with olive oil and place over medium heat. Add diced onion, carrot, and celery. Cook and stir for about 5 minutes or until vegetables have softened a bit. Add diced green chiles, garlic, salt, pepper, chili powder, cumin, and oregano. Cook and stir for another minute or two. Add the chicken broth, enchilada sauce and diced tomatoes. Turn heat up to medium high and bring to a low boil. Reduce heat to low and simmer for 10 minutes to blend flavors.