A computer-based method of determining a migration pathway of a subterranean fluid through a geological volume, wherein determining a migration pathway comprises determining the location of a starting object within the geological volume based on seismic data relating to the geological volume, the starting object defines an initial fluid boundary, data points are distributed through the geological volume, wherein the data points are associated with values of one or more geological attributes derived from seismic data of a seismic survey corresponding to the geological volume, the method including the steps of: defining, on a computer, an expression which determines a change in position of the fluid boundary at the data points over an iteration of the expression based on the values of the one or more attributes; and applying, on a computer, the expression at the data points for successive iterations to evolve the fluid boundary over the successive iterations, whereby the migration pathway of the subterranean fluid through the geological volume is determined from the evolution of the fluid boundary; characterised in that the expression is based on forces that are applied to the fluid boundary and that are derived from the values of the one or more geological attributes, according to the following equation: φ t + F n x ‖ ∇ φ ‖ + F e x ⋅ ∇ φ − F c x κ ‖ ∇ φ ‖ = 0 wherein φ t is a partial derivative with respect to time of a level set function φ that corresponds to the fluid boundary, F n (x) is a force in a direction normal to the object boundary, F e (x) is a force in the direction of the object motion, k is the boundary mean curvature and F c (x) is the curvature force, wherein: κ = ∇ ⋅ ∇ φ ∇ φ = φ 1 2 φ 22 + φ 33 + φ 2 2 φ 11 + φ 33 + φ 3 2 φ 11 + φ 22 φ 1 2 + φ 2 2 + φ 3 2 3 / 2 − 2 φ 12 φ 1 φ 2 + φ 23 φ 2 φ 3 + φ 13 φ 1 φ 3 φ 1 2 + φ 2 2 + φ 3 2 3 / 2 wherein φ i, i = (1,2,3) denotes the partial derivative of φ with respect to x i. defining, on a computer, an expression which determines a change in position of the fluid boundary at the data points over an iteration of the expression based on the values of the one or more attributes; and applying, on a computer, the expression at the data points for successive iterations to evolve the fluid boundary over the successive iterations, whereby the migration pathway of the subterranean fluid through the geological volume is determined from the evolution of the fluid boundary; characterised in that the expression is based on forces that are applied to the fluid boundary and that are derived from the values of the one or more geological attributes, according to the following equation: φ t + F n x ‖ ∇ φ ‖ + F e x ⋅ ∇ φ − F c x κ ‖ ∇ φ ‖ = 0 wherein φ t is a partial derivative with respect to time of a level set function φ that corresponds to the fluid boundary, F n (x) is a force in a direction normal to the object boundary, F e (x) is a force in the direction of the object motion, k is the boundary mean curvature and F c (x) is the curvature force, wherein: κ = ∇ ⋅ ∇ φ ∇ φ = φ 1 2 φ 22 + φ 33 + φ 2 2 φ 11 + φ 33 + φ 3 2 φ 11 + φ 22 φ 1 2 + φ 2 2 + φ 3 2 3 / 2 − 2 φ 12 φ 1 φ 2 + φ 23 φ 2 φ 3 + φ 13 φ 1 φ 3 φ 1 2 + φ 2 2 + φ 3 2 3 / 2 wherein φ i, i = (1,2,3) denotes the partial derivative of φ with respect to x i.