Utilisation of Seismic and Resistivity Data for Fracture Characterisation and Simulation

Characterisation of the heterogeneous naturally fractured reservoirs is an essential and significantly challenging task, especially due to the limited data availability. This paper presents a foundation relationship between P-wave / S-wave velocity and formation resistivity for improved fracture characterisation. Rock matrix and fluid volumetrics are combined with the basic correspondence between formation factor and porosities. Additional variables such as secondary porosity, tortuosity, cementation exponent, partitioning coefficient, crystallisation and mineralisation are also considered to account for variances between the fractured and conventional pore-matrix media. The seismic-resistivity relationship, being novel in fracture heterogeneity, is verified by data from a naturally fractured gas reservoir. The results show very good correlation, highlighting the efficiency of the approach. Analysis on zones of relatively lower correlation suggests that additional variables (lithology and temperature changes) need to be accounted for. Resistivity profile can be obtained at inter-well regions from electromagnetic surveys, thus, allows higher definition of the rock matrix/fracture system and pore/fracture fluids. Comparison of the calculated resistivity profile from the derived equation with the measured values gives a direct indication of changes in lithology (including mineral deposition in fractures, matrix density profile, and hydrocarbon distribution) and this information is highly beneficial at inter-well regions. Key-Words: Discrete fracture network, Seismic, Electromagnetic, Controlled source electromagnetic surveying, Artificial neural network.