Hydrocarbons production installation and method

A heavy-oil-based hydrocarbons effluent production method in an installation that comprises an effluent-lightening fluid injection system at a bottom of a well, an effluent-evacuation pump, a plurality of sensors measuring physical units relating to the installation and an automated device, the method comprising:

• in a phase of stable and continuous production mode, implemented by the automated device, the phase of stable and continuous production mode comprising the optimization of the lightening-fluid injection flow-rate and the regulation of the pump speed according to the physical units and a target production value, the pump speed and the physical units each being comprised within a predetermined range of values, wherein the lightening-fluid injection flow-rate is proportional to a gravity index of the effluent, the automated device performing a real-time calculation of the gravity index of the effluent, wherein the installation comprises a first pressure sensor located at a wellhead and a second pressure sensor located at the pump discharge, measurement of the pump discharge pressure, combined with measurement of the wellhead pressure, allowing the automated device to calculate the gravity index of the effluent.