An integrated hydrothermal process for upgrading heavy oil, the integrated hydrothermal process comprising the steps of: increasing a pressure of a petroleum feed in a feed pump to produce a pressurized feed, wherein a pressure of the pressurized feed is greater than the critical pressure of water; increasing a temperature of the pressurized feed in a feed heater to produce the heated feed, wherein the heated feed is at a feedstock temperature less than 300 deg C; increasing a pressure of a water stream in a water pump to create a pressurized water, wherein a pressure of the pressurized water is greater than the critical pressure of water; increasing a temperature of the pressurized water in a water heater to produce the heated water stream, wherein the heated water stream is supercritical water; mixing the heated water stream and the heated feed in a mixer to produce a mixed fluid; introducing the mixed fluid to a reactor unit to produce a reactor effluent; allowing conversion reactions to occur in the reactor unit, wherein the reactor unit is maintained at a temperature greater than the critical temperature of water and at a pressure greater than the critical pressure of water, wherein the conversion reactions are operable to upgrade the hydrocarbons in the mixed fluid such that the reactor effluent comprises light fractions having a True Boiling Point 90% of less than 343 deg C (650 deg F), heavy fractions having a True Boiling Point 10% greater than 343 deg C (650 deg F), and water; cooling the reactor effluent in a cooling device to produce a cooled fluid, where the cooled fluid is at a temperature less than the critical temperature of water and less than the temperature of the reactor effluent; depressurizing the cooled fluid in a depressurizing device to produce a depressurized fluid, where the depressurized fluid is at a pressure less than the steam pressure corresponding to the temperature of the cooled fluid such that water in the depressurized fluid is present as steam; introducing the depressurized fluid to a flash drum; separating the depressurized fluid in the flash drum to produce a light fraction stream and a heavy fraction stream, wherein the light fraction stream comprises the light fractions and water, wherein the heavy fraction stream comprises the heavy fractions and water, wherein the heavy fraction stream comprises a water content between 0.1 wt% and 10 wt %; introducing the heavy fraction stream to an aqueous reforming unit; and allowing upgrading reactions to occur in the aqueous reforming unit to produce an aqueous reforming outlet, wherein the aqueous reforming unit comprises a catalyst, wherein the catalyst is operable to catalyze the upgrading reactions in the presence of steam, wherein the aqueous reforming outlet comprises a greater concentration of light fraction relative to the petroleum feed. increasing a pressure of a petroleum feed in a feed pump to produce a pressurized feed, wherein a pressure of the pressurized feed is greater than the critical pressure of water; increasing a temperature of the pressurized feed in a feed heater to produce the heated feed, wherein the heated feed is at a feedstock temperature less than 300 deg C; increasing a pressure of a water stream in a water pump to create a pressurized water, wherein a pressure of the pressurized water is greater than the critical pressure of water; increasing a temperature of the pressurized water in a water heater to produce the heated water stream, wherein the heated water stream is supercritical water; mixing the heated water stream and the heated feed in a mixer to produce a mixed fluid; introducing the mixed fluid to a reactor unit to produce a reactor effluent; allowing conversion reactions to occur in the reactor unit, wherein the reactor unit is maintained at a temperature greater than the critical temperature of water and at a pressure greater than the critical pressure of water, wherein the conversion reactions are operable to upgrade the hydrocarbons in the mixed fluid such that the reactor effluent comprises light fractions having a True Boiling Point 90% of less than 343 deg C (650 deg F), heavy fractions having a True Boiling Point 10% greater than 343 deg C (650 deg F), and water; cooling the reactor effluent in a cooling device to produce a cooled fluid, where the cooled fluid is at a temperature less than the critical temperature of water and less than the temperature of the reactor effluent; depressurizing the cooled fluid in a depressurizing device to produce a depressurized fluid, where the depressurized fluid is at a pressure less than the steam pressure corresponding to the temperature of the cooled fluid such that water in the depressurized fluid is present as steam; introducing the depressurized fluid to a flash drum; separating the depressurized fluid in the flash drum to produce a light fraction stream and a heavy fraction stream, wherein the light fraction stream comprises the light fractions and water, wherein the heavy fraction stream comprises the heavy fractions and water, wherein the heavy fraction stream comprises a water content between 0.1 wt% and 10 wt %; introducing the heavy fraction stream to an aqueous reforming unit; and allowing upgrading reactions to occur in the aqueous reforming unit to produce an aqueous reforming outlet, wherein the aqueous reforming unit comprises a catalyst, wherein the catalyst is operable to catalyze the upgrading reactions in the presence of steam, wherein the aqueous reforming outlet comprises a greater concentration of light fraction relative to the petroleum feed.