A geothermal energy extraction subterranean system for extracting heat from a subterranean formation, comprising: - an injection well comprising a first well tubular metal structure arranged in a first borehole providing a first annulus therebetween and extending from surface into the subterranean formation and being configured to inject a working fluid out through a first injection opening into a production area defined in the subterranean formation and thereby generating a heated working fluid, and - a first production well comprising a second well tubular metal structure arranged in a second borehole providing a second annulus therebetween and extending from surface into the subterranean formation into the production area and extracting the heated working fluid through a first production opening, wherein the first well tubular metal structure of the injection well comprises a first annular barrier (20, 20a) and a second annular barrier (20, 20b) configured to expand in the first annulus to abut a wall of the first borehole to isolate a production zone in the production area, each annular barrier comprising: - a tubular metal part mounted as part of the first well tubular metal structure, the tubular metal part having a first expansion opening and an outer face, - an expandable metal sleeve surrounding the tubular metal part and having an inner face facing the tubular metal part and an outer face facing the wall of the borehole, each end, of the expandable metal sleeve being connected with the tubular metal part, and - an annular space between the inner face of the expandable metal sleeve and the tubular metal part, the expandable metal sleeve being expanded to abut a wall of the first borehole by entering pressurised fluid into the annular space through the first expansion opening, the first injection opening being arranged in the first well tubular metal structure between the first annular barrier (20, 20a) and the second annular barrier (20, 20b), and the production zone being arranged between the first well tubular metal structure and the second well tubular metal structure, so that the heated working fluid is extracted in the second well tubular metal structure through the first production opening. - an injection well comprising a first well tubular metal structure arranged in a first borehole providing a first annulus therebetween and extending from surface into the subterranean formation and being configured to inject a working fluid out through a first injection opening into a production area defined in the subterranean formation and thereby generating a heated working fluid, and - a first production well comprising a second well tubular metal structure arranged in a second borehole providing a second annulus therebetween and extending from surface into the subterranean formation into the production area and extracting the heated working fluid through a first production opening, wherein the first well tubular metal structure of the injection well comprises a first annular barrier (20, 20a) and a second annular barrier (20, 20b) configured to expand in the first annulus to abut a wall of the first borehole to isolate a production zone in the production area, each annular barrier comprising: - a tubular metal part mounted as part of the first well tubular metal structure, the tubular metal part having a first expansion opening and an outer face, - an expandable metal sleeve surrounding the tubular metal part and having an inner face facing the tubular metal part and an outer face facing the wall of the borehole, each end, of the expandable metal sleeve being connected with the tubular metal part, and - an annular space between the inner face of the expandable metal sleeve and the tubular metal part, the expandable metal sleeve being expanded to abut a wall of the first borehole by entering pressurised fluid into the annular space through the first expansion opening, the first injection opening being arranged in the first well tubular metal structure between the first annular barrier (20, 20a) and the second annular barrier (20, 20b), and the production zone being arranged between the first well tubular metal structure and the second well tubular metal structure, so that the heated working fluid is extracted in the second well tubular metal structure through the first production opening. - a tubular metal part mounted as part of the first well tubular metal structure, the tubular metal part having a first expansion opening and an outer face, - an expandable metal sleeve surrounding the tubular metal part and having an inner face facing the tubular metal part and an outer face facing the wall of the borehole, each end, of the expandable metal sleeve being connected with the tubular metal part, and - an annular space between the inner face of the expandable metal sleeve and the tubular metal part, the expandable metal sleeve being expanded to abut a wall of the first borehole by entering pressurised fluid into the annular space through the first expansion opening,