Abstract: Systems and methods for casing drilling riserless sections of a subsea bore may include casing drilling a section of a bore for a casing of the subsea bore to a predetermined depth. The method also may include, while casing drilling the section of the bore, obtaining information indicative of pore pressure and fracture pressure of a geological formation through which the section is casing drilled, and determining a pressure range based at least in part on the pore pressure, the fracture pressure, and a modification to mechanical properties of the geological formation due to the casing drilling of the section. The method further may include selecting, based at least in part on the pressure range and the predetermined depth, a pressure of the bore for casing drilling the section.