Simulation And Application Of Dual Laterolog In Fracture Formation

In fracture formation such as carbonate and volcanic rocks,dual laterolog plays an important role in fracture identification and evaluation.In order to further study the response characteristics of dual laterolog in fracture formation and establish interpretation model,this paper carries out the numerical simulation and physical simulation experiments of dual laterolog in scaling-down fracture formation and proposes a real-time extraction method of carbonate fracture parameters by using dual laterolog data,based on the idea of "numerical simulation-physical simulation-application".The article makes a reasonable abstraction and simplification of complex geological model,after carefully analyzing the physical properties of fractures.According on electromagnetic theory,structure and logging principle of the dual laterolog,a mathematical model is established and the article uses 3-D finite element method to simulate the dual laterolog response of single fracture and parallel frature with equal spacing.Based on the numerical simulation results,the paper optimizes the scaling-down parameters of the formation model and establishes the scaling-down dual laterolog physical simulation system.To realize the physical experiment controlled,the bedrock is simulated by Nacl solution,and the cracks are simulated by galvanized sheet.Physical simulation results and numerical simulation results are mutually validated.After systematically studying the influence of fracture on the response of dual laterolog,we found specific relationships between dual laterolog responses and fracture dipping angle,fracture aperture,bedrock resistivity and fluid resistivity in fractures.According to the basic vector theory in functional analysis,we select a "complete" base vector such as polynomial to fit the relationship between dual laterolog values and fracture parameters of the formation,and obtain a set of simplified mathematical expression of dual laterolog response in fracture formation.By using simplified mathematical formula and the idea of mathematical dichotomy,we obtains an improved fast calculation method of fracture parameters in fractured formation.Compared with the traditional iterative inversion algorithm,it avoids the repeated 3-D finite element numerical simulation of dual laterolog response in fracture formation,greatly reduces the time of calculating fracture parameters,thus realizes the real-time extraction of fracture porosity and the rough judgement of fracture dipping angle.The improved fast calculation method can be conveniently and quickly applied to the actual logging data processing and interpretation.