Preheat oven to 375 degrees Fahrenheit. In a Dutch oven cook two-thirds of the celery and onion in hot oil over medium heat for 3 minutes. Add chicken, pepper, thyme and salt to Dutch oven; cook for 2 minutes. Add the water. Bring to boiling; reduce heat. Simmer, covered, for 20 to 25 minutes until chicken is no longer pink.