The invention relates to a method of controlling the production of oil or gas from a formation (1) comprising that a first and second drilled production well (105, 110) are formed next to each other that extend essentially horizontally, that, at the drilled production wells, a further drilled well (115) is formed that extends between the first and the second drilled production well (105, 110), that the production of oil or gas is initiated, and that, while oil or gas is being produced, a liquid is conveyed to said further drilled well (115) and out into the formation (1) for a first period of time T.sub.1. The invention is characterised in that the pore pressure of the formation is influenced during the period T.sub.1 with the object of subsequently controlling the formation of fractures along a drilled well, typically across large distances in the reservoir. Such influence is accomplished partly by production in adjacent wells, partly by injection at low rate without fracturing in the well in which the fracture is to originate. Injection at low rate presupposes that an at least approximated determination is performed of the maximally allowable injection rate I.sub.max for the period T.sub.1 in order to avoid fracturing ruptures in said further drilled well (115) when liquid is supplied by the injection rate I for the liquid supplied to the further drilled well being kept below said maximally allowable injection rate I.sub.max for said first period of time T.sub.1 when the relation .sigma.'.sub.hole,min<=.sigma.'.sub.h has been complied with.