Heat a large, heavy duty skillet over medium-high heat. Add oil, and swirl the skillet to coat the bottom. Add the shrimp into the skillet and arrange in one even layer. Cook for about 4 minutes, flipping halfway through, or until the shrimp is pink, but not 100% cooked through.
Make a well in the center of the skillet by moving the shrimp to the edges. Add your butter and garlic into the center of the pan, and cook for about 1 minute, or until the butter is fragrant.
Add in the chili powder, paprika, celery salt, oregano, and salt and pepper. Toss the shrimp to coat in the garlic, butter, and spices. The shrimp should be cooked all the way through by now, but if it isn't, just continue cooking it on medium until fully cooked.