Add the remaining 2 tablespoons of olive oil to the skillet and add the onion, carrots, celery and garlic. Cook over moderate heat, stirring occasionally, until starting to brown, about 8 minutes. Add the sugar, wine, vinegar, orange juice, capers and almonds and bring to a boil. Return the chicken to the skillet, skin side up. Cover partially and simmer over low heat until the chicken is cooked through, about 35 minutes.