Muddy horse corral need help with drainage?

I have a 30x30 corral that is getting alot of water build up. I need to get the water moved out of the area. I though about putting a french drain in, but my nearest negative fall to daylight it is about 200' away. I also thought about a putting a large dry well but i have very heavy clay that doesn't drain well. i need to clear out about 6" of mud. Any ideas would help, also not sure exactly what to put on top, layer with drain rock then sand or all sand.