Abstract: A method of hydraulic fracturing of a hydrocarbon reservoir in a rock layer uses a method of providing a reservoir description. Firstly, a reservoir description is provided for the hydrocarbon reservoir. This reservoir description comprises a distribution of stresses within a rock layer affecting propagation of a hydraulic fracture. This reservoir description can be used to calculate a fracture plan to for hydraulic fracture of the hydrocarbon reservoir according to the distribution of stresses in the reservoir description to provide one or more predetermined fracture properties. Hydraulic fracturing of the hydrocarbon reservoir can then follow according to the fracture plan. A method determines minimum horizontal stress in a rock region.