high-density medium density and low density sand for exploring more oil and gas , Ceramic Proppant is divided into ... , 12-20 mesh, 16-20 mesh, 16-30 mesh, 20-40 mesh between 30-50 mesh, 40-60 mesh, 40-70 mesh ... be closed because of the released force when extracting oil by high closed fracturing, thereby to maintain the high conductivity of ...