Oil-base Mud Micro-resistivity Scanning Imaging Methods

Formation micro-resistivity Image well logging technology play an important role in the field of oil and gas exploration, who can evaluate the cracks in thin-layer and the storage capacity of oil and gas fields, also, it can help geologists identify lithology and sedimentary structures and stratigraphic information. Formation Micro-resistivity Image tool originally use soil conductive drilling mud, who can drive conduction current to link mud, formation and instrument together. However, with the exploration to the selection of an extension of the continental shelf and the development of logging technology, oil-based mud can effectively adapt to the new logging environments, it has to increase drilling efficiency to prevent the collapse of the borehole, to make the sidewall more rules and so on, but in oil-based mud condition,the current loop is destroyed. High frequency alternating current can solve this problem. Traditional micro-resistivity image tool only need to use the Poisson equation for finite element electromagnetic modeling and simulation, and the introduction of alternating current makes the need to use the wave equation for finite element modeling and simulation, therefore there are fundamental change from principles of conduction to simulation mode. Oil-based mud micro-resistivity imaging tool’s design often emphasis on the resolution and detection depth, but in the electrode size, frequency and other parameters, it has inherent contradictions, and often can not be together.The research of this subject is based on the above background, computer simulation program has been edited for oil-based mud micro-resistivity logging instrument multi-parameter optimization of the design, calibration data, fracture evaluation. This paper use capacitive coupling method and four-point measurement as a basic measurement methods to optimize the parameters of the tool. Combined with the characteristics of the two methods, innovative instrument comes true, it can successfully not only get high resolution multi-frequency selection but also different depth of investigation as a result of introduction of multi-frequency and multi-return electrode. This paper proposes a dual-frequency with low-frequency correction method to eliminate the influence of oil-based mud. Capacitive coupling method and a four-point measurement method are used to design appropriate instrument pad. The pad structure, the overall instrument parameters and mud parameters influencing factors have been optimized for the resolution, probing depth. After that, imaging experiment has been made.In this paper, based on the information of water-based mud micro-resistivity imaging logging, the study of crack evaluation has been made and get a function.The subject of research and design work can provide theoretical guidance for the key technologies in the design of oil-based mud micro-resistivity logging tool and a solid foundation for the next step in the design.