Response of Dual Laterolog to Fractures in Fractured Carbonate Formation and Its Interpretation

The estimation of fractures is a key to the evaluation of the fractured carbonate reservoirs. Many obstacles are present for the evaluation of this kind of reservoir because of its heterogeneously-distributed fractures and anisotropies. A three-dimensional numerical algorithm based on a macro-isotropic anisotropic model, a fast fracture-computing method, may simulate the responses of the dual-laterolog in fractured formation. Firstly, the apparent conductivity of dual-laterolog is linearly related to the porosity of fracture and to the conductivity of pore fluid. Secondly, the amplitude difference of the deep and shallow apparent resistivity logs was dependent mainly on the dip angle of the fracture. Thirdly, the response of dual laterolog of formation with dip angle fractures is approximately depicted as a function of bulk resistivity of rock, porosity of fracture and conductivity of fracture fluid, for the rapid computation of the fracture porosity. The research data show that the fracture parameters determined by the dual laterolog coincide well with the formation micro-image log.