Advancements in Oil-Based Mud Micro-Resistivity Imaging - How Enhanced Dynamic Range Improves Feature Detection in Low and High Resistivity Formations

Abstract Subsurface imaging is essential in exploration and field development, primarily for resolving and integrating geological complexities to the reservoir structures & depositional environments. Acquiring high resolution image data in non-conductive drilling muds has been one of the key challenges which led to the development of a new measurement technique in recent generation Oil Based Mud (OBM) imaging tools. Further challenges arise while acquiring high resolution OBM image in maintaining the quality across a broader formation resistivity range and with coverage in large borehole sizes. Among all, resolving features in both the high and low end of formation resistivity ranges was one of the most difficult to achieve. Qualification of the new generation 8-pad / multi-frequency micro-resistivity imager tool was the primary objective which was deployed throughout the field-test runs. The tool was deployed in a number of selective wells covering a wide range of trajectories, hole sizes, lithologies and formation resistivities, stand-alone or combined with other existing OBM imaging technologies that utilizes similar or different measurement techniques. The result of the field-test runs outline the added value of each measurement independently and when compared and/or combined with others. This paper delineates the principal characteristics of the new generation high resolution OBM imaging tool and presents key findings from the acquired image logs in variety of formation types, resistivity ranges and trajectories. Illustrative examples underscore the enhancement in image quality, dynamic range, coverage as well as the ability to resolve features for successful geological interpretation, decision-making, and risk management. The results from this field testing marks an outstanding milestone on the range of apparent formation resistivities that can be covered using a higher number of frequencies with a broader range, show the value of combining different OBM imaging technologies for achieving optimum results.