Heat oil in large pot and cook bacon until crisp. Stir in onions and celery and cook until tender. Stir in carrots, bay leaf, basil and oregano and toss to coat. Pour in chicken stock and tomatoes bring to a simmer. Cook for 15 minutes until potatoes are tender. Stir in green beans and shells. Cook for 6-8 minutes or until pasta is tender. Season to taste.