The Buick Piston Rings set has three of them present that have to be correctly installed on each piston they are placed on. The upper two piston rings are called the compression rings. They are what seal the moving piston and the cylinder walls so none of the gases can pass by this joint when the explosion occurs in the combustion chamber on your Buick engine.
The lower Buick piston ring is the oil ring. It is made of three rings that work together so the cylinder walls and the piston are properly lubricated with the engine oil in the reduction of friction as this component moves up and down.
When the blue smoke is billowing out of the tail pipe, the most likely culprit is the compression piston rings. They will in time lose their ability to contain the gases in the combustion chambers and a reduction in the amount of force the explosion produces by leaking by them. As a side effect, the oil from the oil rings seeps into the combustion chamber and is the source of the blue oil smoke you see emanating from your Buick's exhaust system.
A compression tester has to be used so the owner will know the amount each cylinder is producing. As quick check place a finger or thumb over the spark plug hole and have the engine turned over. If your hand is forced away from the hole, it has sufficient compression to operate. If you can hold your hand over the hole, you have only minimum compression and the piston rings should be replaced.
The replacing of the piston rings on your Buick engine does require each of the pistons to be pulled. The cylinder also has to be honed before a new seal can be formed in the combustion chamber.