The d-realisation number of a graph G counts, roughly speaking, the number of equivalent d-realisations of a generic d-realisation of G. It is known that this number is finite if and only if G is d-rigid. For a minimally 2-rigid graph, we give a way of computing this number as the tropical intersection number of the Bergman fan of the graphic matroid of G with its “reciprocal”. This description allows us to bound the realisation number with some matroid invariant.