Deep-directional-resistivity (DDR) logging-while-drilling (LWD) technology has gained acceptance as an efficient method for horizontal well landing, geosteering, and reservoir and fluidcontact mapping. The largest part of the value lies in the automatic inversion of the measurements, improving the detection of geologic and fluid boundaries within a radius of investigation of more than 30 m around the wellbore in real time. The tool and its sensors were designed to acquire a data set with sensitivity to a number of formation properties ensuring the concurrent deployment of a robust inversion. Based on this, an inversion method implemented on computer clusters statistically samples (or explores) the multidimensional inversion space, returning the distribution of formation models that fit the available data. The most noticeable aspect to operators is that this is done without introducing bias. There is no need to commit to a number of layers or to the position, thickness, resistivity, or dip of the layers to generate the continuous images on which all DDR interpretation is based, which translates into several theoretical and practical advantages. In practice, this gives users a higher level of quality control and more confidence in interpreting the subsurface within a larger diameter around the wellbore, which is useful for integrating the information into a geomodel. This derisks current and future operation, improves real-time and planning decisions, and ultimately drives better well placement, completion, production, and return on investment.

The last decade has shown a significant development in resistivity measurement technology providing directional resistivity at a larger scale than conventional logging tools. The latest development can identify resistivity contrasts ten's of meters around the wellbore. Statoil has tested deep look-around resistivity on a range of fields during the last 2 years and recorded data in more than 10 wells on the Norwegian Continental Shelf. The look-around images provides information at a scale that bridges the gap between conventional logging and seismic and adds important new pieces to the reservoir characterization puzzle. In good reservoir conditions, resistivity contrast up to 30 m away from the well-bore has been observed. This study will focus on results from the Visund and Åsgard fields, and will demonstrate how the device was used in a range of different applications in the geosteering operation: Detection of the reservoir boundary up to 20m TVD away. Detection of oil bearing reservoir from within underlying shale, through a water zone. Detection of Gas-Oil Contact (GOC). Detection of Oil-Water Contact (OWC) up to 20m TVD away. Detect faulting of the reservoir. These examples will highlight why deep look-around resistivity is a step change related to the possibility for doing pro-active well placement of highly deviated wellbores as well as for gaining a larger reservoir understanding. The imaged variation in resistivity contrasts can be related to geologic zonation and fluid content on the reservoir scale, which opens up a much better cross-disciplinary communication between geophysicists, geologists, petrophysicists and reservoir engineers. Finally, the deep resistivity images contribute in optimization of completion solutions when incorporating information on the reservoir scale.

The advent of deep-reading directional electromagnetic logging-while-drilling measurements brings opportunities in imaging complex formations around the wellbore. In this context, basing the inversions on an assumption of a layered medium is not always sufficient to decouple geometrical effects in complex formation scenarios.Rather than attempting to invert all variables of a generic 2D formation model simultaneously, we describe in this paper how the use of 2D inversions can be enabled through a robust workflow specifically designed for a class of formation models, in this case the angular unconformity. We demonstrate how the successive application of 1D inversion to subsets of tool data gradually builds a formation model for use as input to a 2D inversion, which accounts for complex couplings present in the data in such environments.The validity and the performance of the method are established through synthetic and field datasets. IntroductionSince the introduction in 2005 of deep and directional logging-while-drilling (LWD) electromagnetic (EM) measurements, thousands of wells have been geosteered based on remote boundary imaging, in a variety of reservoirs and geological environments. The standard processing applied to the measurements is a multilayer 1D inversion. Although this type of processing is valid in a large number of cases and has supported many successful operations, this paper introduces a different way of processing measurements to produce a more structured image of the formation around the wellbore and successfully address nonlayered scenarios in which the risks associated with the errors in running the standard processing might increase beyond desirable levels.We present a processing workflow running automatically through multiple inversion steps and minimizing the bias introduced by users. The steps gradually build a richer model of the subsurface, while introducing measurements with sensitivities matching the model features added at each step. The concept was implemented and tested on a specific family of nonlayered scenarios, the angular unconformity.The first sections summarize the LWD tools and the traditional 1D and 2.5D forward modeling and inversion concepts used in the workflow and throughout the industry. Then, the characteristics of the angular unconformity scenarios are defined, before some arguments are given to justify the need for an imaging workflow rather than a single inversion in the first place as is standard. The workflow steps are detailed next, and in the final sections the results and stability on synthetic and field examples are discussed.

New technologies have been developed to achieve a higher degree of accuracy in well positioning as operators have been drilling increasingly challenging hydrocarbon pockets.The Nini East Field, Danish North Sea sector, represents a significant drilling challenge. The target is a postdepositionally remobilized sand reservoir of 2 15 meters thickness. Because of the reservoir's remobilized nature and its low resistivity, none of the standard well placement methods or the current bed-boundary mapping tools were suitable solutions for the well objectives. Previous wells drilled in this type of reservoir have been marginally economical due to sidetracks and net-pay ratios below 0.5.In view of these challenges, DONG E&P decided to collaborate to the field test of the next generation bed-boundary mapping tool to geosteer their two upcoming production wells. The technology currently in field test provides a real-time mapping of the reservoir several meters away from the wellbore. As the depth of investigation of the tool is within the same range as surface seismic measurements, the two data sources were integrated while drilling to provide look-ahead information.The two producers achieved an outstanding 0.99 and 0.96 net-pay ratio with no sidetracks or delays and were completed within budget.The inversion processing of deep directional resistivity measurements clearly shows the capability of this new generation tool to map the internal variations of the reservoir structure, enabling further understanding of its nature and depositional history and allowing optimization of the field development.

Statoil has played a key role in testing and development of the new ultra-deep directional resistivity (DDR) logging while drilling (LWD) measurements for high angle and horizontal wells the last 4 years. Inverted resistivity images provide an overview of geological structures and fluid contacts tens of meters around the wellbore. The ultra-deep look around measurements, sensitive to resistivity contrasts up to 30 m away or even more in favorable conditions, are a step change, when it comes to possibility to position the wellbore strategically in the reservoir and to characterize reservoir structure and properties. This paper will present how the new DDR measurements have been applied with success in an operating license on the Norwegian Continental Shelf (NCS). Long horizontal wells in the reservoir sections have been identified as a key strategy to increase recovery. The main benefits from the DDR measurements in the license have been to maximize reservoir exposure by active geosteering, to optimize well placement above oil-water contact, and to increase subsurface understanding which is important input for future well plans.The DDR measurements are already a commercial service with regard to well placement and reservoir landing. Statoil is however also actively pushing for improved reservoir characterization, by coupling geomodels and DDR modeling and inversion software. This paper will also present how standard LWD logs and images can be combined with the DDR inversion results, to build a near-wellbore 3D structural model supporting all available data. This is an important step towards an extended use of the new data not only for well placement, but also for increased subsurface understanding and geomodel update.