Numerical And Experimental Simulations Of Multi-Array Azimuthal Laterolog Sonde Responses In Fracture-Vug Reservoirs

A Multi-array Azimuthal Laterolog Sonde(MALS)is presented here which was designed to evaluate fractures and caves occurrences,fracture-developed zones in carbonates,volcanics or some other complex reservoirs.Through the comparative analysis of the 3D FEM numerical and experimental simulations in fractured reservoirs,we studied the responses of MALS with different fracture and vug parameters.This paper introduced a novel MALS tool which combines the laterolog(which can realize radial investigation)with the azimuthal resistivity together.Its advanced manufacturing techniques shortens the length of tool while maintaining its excellent vertical resolution,which is greatly convenient for actual logging.The length of MALS used here is 6 meters,and there are four working modes(AL0 to AL3)which can be operated simultaneously,and each mode represents an investigation depth,six azimuth resistivity curves.In total,there are 21 resistivity curves including five lateral resistivity curves.The MALS can more accurately characterize in highly-deviated wells and horizontal wells,thin interbed and fractured and caved reservoirs which distinguishes primary fracture and induced fracture caused by drilling.According the resistivity supported by MALS,we can fulfill well bore imaging.In numerical simulations,we established the simplified mathematical model.Variational method could naturally convert complex segmentation into a variational functional optimization problem.Finite element and COMSOL method calculate the mathematical model.We set up the resistivity formula depending on model's requirements,discretized the computational domain,and pick an interpolating function.The frontier solution is applied to achieve the forward calculation finally.To verify the effectiveness of MALS response in fractured reservoir,we designed a scaled-down MALS experimental instrument according to the similarity criterion of the experimental model.The environment of fractured and caved reservoir also has been simulated during the experimental use of the instrument.The study found that the response of MALS in fractured reservoir relates with dip angle,opening and the contrast of resistivity.In caved reservoir,the radius,resistivity and distance effect the response of tools.