White Bean And Pasta Soup

Name: White Bean And Pasta Soup
Ingredients: 3 tablespoons olive oil; 2 cups chopped onions; 2/3 cup chopped carrot; 2/3 cup chopped celery; 3 1/2 cups (or more) water; 2 to 2 1/2 cups cooked white beans with 3/4 cup reserved cooking liquid; 1 large tomato, seeded, finely chopped; 1 cup small pasta (such as farfalline); 1/3 cup chopped green onions (white and pale green parts only; about 2); Extra-virgin olive oil (for drizzling)