Warm the oil in a medium pot set over medium heat. Add the shrimp shells, onions, carrots, and celery and cook for 15 minutes, until lightly browned. Add the garlic and cook for one more minute. Add 1 1/2 quarts water, the wine, tomato paste, thyme, 1 tablespoon salt, and 1 1/2 teaspoons pepper. Bring to a boil, lower the heat, and simmer for one hour. Strain through a sieve, pressing on the solids. You should have approximately 1 quart of stock. If not, add enough water or white wine to make 1 quart.
Cool completely, transfer to containers, and refrigerate for up to 3 days or freeze for up to 1 month.