Can car jack go under the oil pan 1991 buick park ave?

I wouldn't do that! You may puncture, crack or dent the oil pan and have a bigger problem. Even if you use a board to spread the load around, the weight of the engine will squeeze the gaskets or deform the pan and probably cause oil leaks later. I would look for other areas to use if you must raise the engine. Typically they use a hoist to lift it. This is just my humble opinion and you might check with a good mechanic to get a better answer. Heck no, don't, use the frame rail, never the oil pan.