This disclosure provides equipment and processes for ground heat exchange. Embodiments of the ground heat exchange system may comprise a geothermal well that includes an inner tube positioned coaxially inside a borehole in geologic units, a substantially-liquid impermeable outer liner sealed at the bottom, and a liquid supply system. The outer liner may include one or more layers of a substantially-liquid impermeable fabric or coating. A fluid such as water is supplied by the liquid supply system and flows co-axially through the inner tube. The fluid pressure in the annulus between the inner tube and the outer liner presses the outer liner against the borehole wall, providing sealing contact and preventing interconnection of aquifers of the geologic units.