The invention is a method for defining the development conditions of a hydrocarbon reservoir by updating a velocity model by means of log data. A first seismic depth image representative of the reservoir is established by using seismic data and a velocity model. A series of log data is acquired from wells. Differences between seismic reflector depths observed in the first seismic depth image and depths for these reflectors identified in the wells are measured. The velocity model is modified to minimize these errors, using a prestack kinematic inversion technique allowing constraints to be taken into account. A new seismic depth image from which the development conditions of the hydrocarbon reservoir are determined is deduced therefrom. The invention has application for hydrocarbon reservoir development.