Modelling a Fractured Dolomite Reservoir Without Substantial Information – a case study

A fractured dolomite reservoir of an alpine thrust nappe, influenced by several deformations, was modelled for simulation requirements. A three step workflow (data analysis - conceptual model - reservoir model) was initiated to deal with the limited data situation. Log, core and test data as well as 3D seismic were insufficient to describe the reservoir situation. An outcrop study extended the limited data set and resulted in 6 deformation cycles, several fracture and fault rock types. The rock types were grouped to 4 pseudo facies types (matrix, micro-fractured, fractured and fault rock) and log-calculated porosity was split up on these 4 pseudo facies. Using different synthetic phi/k functions permeability was calculated for each pseudo facies. A large number of production tests approved the calculated permeability. As a dual porosity / dual permeability approach was planned for simulation, the 4 pseudo facies types had to be combined in two sets of contrasting properties. Fault rock with very high permeability represents the simulation fracture set, whereas matrix, microfractures and fractures with poor to medium permeability act together as simulation matrix set. Both sets have their own phi and k properties. Without major adjustments a good history match was achieved.