Heaat oil in a large Dutch oven or stockpot on medium. Add onion, carrots and celery; season with salt and black pepper and cook until soft, about 8 minutes. Add jalapeno, paprika and thyme and cook for 1 minute, stirring well. Add 3 cups water, increase heat and bring to a boil. Add potatoes and reduce to a simmer until just tender, 7 to 8 minutes. Add corn and milk, season with salt (1/4 tsp. minimum) and black pepper, and simmer 3 more minutes. Remove from heat.
Pour 3 cups corn mixture into a blender, covering opening loosely with a kitchen towel to prevent splatters (steam from the hot liquid may cause the blender's lid to pop off) and puree. Transfer puree back to pot, stir to combine and return to medium heat; bring to a simmer.
Add scallops to pot and simmmer for 3 minutes(time should begin when liquid resumes to simmer). Add shrimp and simmer for 2 minutes or until shellfish are opaque in center. Remove from heat and taste for seasoning. Ladle into bowls, sprinkle with scallions, dividing evenly and serve.