Over the last two decades, the continuing integration of distance-to-boundary logging while drilling (LWD) workflows with the directional drilling processes, has dramatically improved geosteering of deviated and horizontal wells. However, the interpretation of underlying propagation azimuthal electromagnetic measurements has remained challenging in complex thin and multi-layered geologies. Recent technology advancements in LWD electromagnetic propagation resistivity coupled with significant software enhancements provide an opportunity for improving the formation evaluation to reduce wellbore position uncertainty, accurately detecting physical parameters such as layer resistivity and anisotropy, formation dip and azimuth. A newly developed multilayer mapping-while-drilling service with full azimuthal sensitivity is introduced for use in geosteering and formation evaluation while drilling applications. The tool offers the industry's first combination of axial, tilted and transverse antennas to produce a complete measurement set to enable the interpretation of complex and anisotropic formation. Advanced application algorithms are used to calculate a high-definition map of the formation providing horizontal and vertical resistivity (anisotropy), as well as dipping angle and azimuth. Furthermore, the tool can provide deep resistivity borehole images while drilling in real time. The new measurement set, more comprehensive than any other directional propagation resistivity tool in the industry, is discussed in detail. The measurements, combined with a new deterministic inversion, enable reconstruction of the resistivity of up to eight formation layers, and significantly outperforms existing directional propagation resistivity services. The new measurements and data processing workflow are demonstrated with several synthetic and field data. Examples show that this newly developed tool can provide a reliable two-in-one service: geosteering and advanced formation evaluation.

Faulting is one type of structural trap for hydrocarbon reservoirs. With more and more fields moving toward the brownfield or mature operations stage of life, the opportunity to target bypassed or attic oil in the vicinity of bounding fault(s) is becoming more and more attractive to operators. However, without an effective logging-while-drilling (LWD) tool to locate and map a fault parallel to the well trajectory, it has been challenging and potentially high risk to optimally place a well to drain oil reserves near the fault. Operators often plan these horizontal wells at a significant distance away from the mapped fault position to avoid impacts to the well construction and production of the well. Often, the interpreted fault position, based on seismic data, can have significant lateral uncertainty, and uncertainties attached to standard well survey measurements make it challenging to place the well near the fault. This often results in the wells being placed much farther from the fault than expected, which is not optimal for maximizing recovery. In other cases, due to uncertainty in the location of the fault, the wells would accidentally penetrate the side faults and cause drilling and other issues. Conventional remote boundary detection LWD tools do not assist with locating the fault position, as they only detect formation boundaries above or below the trajectory and not to the side. In this paper, the authors propose a novel approach for mapping features like a fault parallel to the well trajectory, which was previously impossible to map accurately. This new approach utilizes a new class of deep directional resistivity measurements acquired by a reservoir mapping-while-drilling tool. The deep directional resistivity measurements are input to a newly devised inversion algorithm, resulting in high-resolution reservoir mapping on the transverse plane, which is perpendicular to the well path. These new measurements have a strong sensitivity to resistivity in contrast to the sides of the wellbore, making them suitable for side fault detection. The new inversion in the transverse plane is not limited to detecting a side fault; it can also map any feature on the transverse plane to the well path, which further broadens the application of this technology. Using the deep directional resistivity data acquired from a horizontal ultra-ERD well recently drilled in the Wandoo Field offshore Western Australia, the authors tested this approach against the well results and existing control wells. Excellent mapping of the main side fault up to 30 m to the side of the well was achieved with the new approach. Furthermore, the inversion reveals other interesting features like lateral formation thickness variations and the casing of a nearby well. In addition, the methodology of utilizing this new approach for guiding geosteering parallel to side fault in real time is elaborated, and the future applications are discussed.

Deep directional resistivity logging-while-drilling technology and its measurement processing are instrumental in strategic well placement, landing, geosteering, and reservoir understanding. However, since the measurements are truly at the reservoir scale, reservoir complexities limit the applicability of 1D and sometimes even 2D interpretation models and inversions. A new full-3D imaging inversion is introduced to accurately map reservoir sections where 1D and 2D models are not adequate to represent the reservoir. The imaging inversion uses a 3D EM simulator and accounts for both resistivity and resistivity anisotropy and is fully consistent with the 1D and 2D inversion results in sections of lower complexity. The inversion is validated with a realistic 3D reservoir model and applied to field datasets from the North Sea, revealing complex 3D detail consistent with all the data.

The Al Shaheen field has been on production for 25 years and is developed using waterflood and ERD wells, some of which are openhole. Production logging Tools are occasionally required to assess waterflood performance, and the implementation of appropriate mitigation steps. Wellbore architecture and offshore facility limitations make conventional production logging challenging. Therefore to identify swept zones or non-conformances an ERD producer and injector, a novel data acquisition plan based on Ultra-deep resistivity LWD measurements and more conventional open hole measurements was designed to overcome these challenges. Ultra-deep directional resistivity measurements recorded in the injector well were used to map the reservoir structure and fluid distribution up to 100 feet above and below from the injector well. In addition to time lapse resistivity logging, a novel 2D deep azimuthal imaging using extended set of ultra-deep directional resistivity measurements with 3D sensitivities were used to identify movement of fluid in horizontal direction towards the producer well. Full 3D modeling of deep directional resistivity responses was performed before the data acquisition to evaluate sensitivities and signatures of invaded fracture swarms of variable fracture density on measurements and real-time interpretation based on 1D inversions. The 2D deep azimuthal imaging using the extended 3D set of ultra-deep directional resistivity measurements provided resistivity maps used to identify the fluid fronts and evaluate movement of fluids in lateral direction and heterogeneities not only above and below but also left and right up to 100ft away from the wellbore. The identified flooded zones were consistent with time-lapse resistivities. The 3D modeling and 1D inversion helped to understand patterns in real-time deep directional resistivity interpretation. Detailed analysis of resistivity responses and original while drilling images confirmed identified fracture swarm zones. Besides overcoming challenges with conventional production logs, the methodology provides a unique 3D view of the reservoir from LWD logs at the scale of inches to 100ft. The case study demonstrates the potential of newly developed deep azimuthal 2D imaging using ultra-deep directional resistivity data to refine the 3D structural interpretation and evaluate the fluid distribution up to 100 feet away from the injector well. This information will be critical to build for the first time consistent 3D interpretation from the wellbore to reservoir scale, calibrating 4D seismic in challenging Middle East carbonates reservoir and bridging the gap between the time-lapse conventional resistivity logs and 4D seismic.

Deep-directional electromagnetic (EM) logging-while-drilling technology can map reservoir boundaries and fluid contacts for strategic geosteering, reservoir navigation, and more recently, for reservoir characterization. The inversion-based resistivity mapping is used to make real-time geosteering decisions and to refine and update the reservoir model during and after drilling. Traditional 1D and 2D inversion approaches ignore the lateral changes of the reservoir, which are contained in the azimuthally sensitive measurements and only provide a longitudinal 2D representation of the 3D reservoir structure around the well. A new 2D lateral imaging inversion uses the full azimuthal sensitivity of the measurements to map the vertical and lateral resistivity heterogeneities around the wellbore. A 2.5D EM solver is run in a Gauss-Newton optimization to reconstruct the measurements in complex scenarios and determine the 2D anisotropic resistivity distribution in an imaging plane along with the orientation of the formation invariant direction with respect to the wellbore. Continuous 2D imaging along the well path generates a 3D reservoir resistivity map in the proximity of the wellbore.

The performance and potential ambiguity in casing thickness evaluation using pulsed eddy current (PEC) measurement interpretation based on response time to depth mapping is assessed for realistic downhole settings. Casing eccentering sensitivity analysis based on 3D fmite-element method is performed for PEC sensors of variable lengths. The effect of defect size, approaching defects and casing collars for three casing configurations is also studied to highlight the increased interpretation uncertainty in realistic noncentered environments.

The concept of apparent thicknesses is introduced for the inversion-based, multicasing evaluation interpretation workflow using multifrequency and multispacing electromagnetic measurements. A thickness value is assigned to each measurement, enabling the development of two new preprocessing algorithms to remove casing collar artifacts. First, long-spacing apparent thicknesses are used to remove, from the pipe sections, artifacts ("ghosts") caused by the transmitter crossing a casing collar or corrosion. Second, a collar identification, localization, and assignment algorithm is developed to enable robust inversion in collar sections. Last, casing eccentering can also be identified on the basis of opposite deviation of short-spacing phase and magnitude apparent thicknesses from the nominal value. The proposed workflow can handle an arbitrary number of nested casings and has been validated on synthetic and field data.

Summary Success of horizontal infill wells targeting bypassed zones are challenged by uncertainties in the reservoir description but also by fluid content variation generated by differences in sweep efficiency over time. Optimizing well placement of such producer wells has a direct impact on cost and recovery where more marginal and complex targets are a natural consequence of increasing number of infill wells. This could, also, potentially unlock targets not accessible today with currently used methods and technologies. Innovative interpretation methods based on efficient measurements to map structure and fluids around high angle and horizontal wells while drilling are critical for future success in a marginal, but increasingly strategical, business on the Norwegian Continental Shelf. This paper presents field case results of a new inversion method called 2D azimuthal inversions providing 2D azimuthal resistivity images in a plane transverse to the wellbore. This algorithm takes advantage of the full 3D sensitivities of ultra-deep directional resistivity measurements to map the 2D resistivity distribution in an imaging plane and find the dominant formation trends. Continuous deep azimuthal 2D imaging along the well path generates a 3D resistivity distribution in the proximity of the wellbore. Thus, for the first time resistivity distributions can be interpreted laterally to the well tens of meters from the wellbore. This is key information to update local 3D geomodels around the wellbore and to identify structural and potential flooding events laterally to the well. Sidetrack planning is another obvious application of this new inversion result that also will be presented in this paper. The future challenge is to develop effective tools for updating local 3D geomodels during drilling to validate advanced interpretation based on 2D deep azimuthal inversions, as well as to quantify artefacts on 1D and 2D inversions produced by 3D effects. Operator and service companies need to work on effective workflows together to fully exploit the measurement potential for 3D mapping of geologic formations and fluids around the well.

Summary The development of the EMLA system adds a new powerful real-time LWD tool to the toolbox. The true look-ahead sensitivity makes it possible for the first time in the industry to react timely to changes in formation resistivity several meters to tens of meters ahead of the bit for vertical and low-angle wells. It will be demonstrated through field applications how the technology has reduced the risk and cost of drilling operations, by assisting in optimizing the well design.

Abstract The Byrding asset on the Norwegian Continental Shelf (NCS) successfully drilled a two-branched horizontal producer in a structuraly complex area with many faults, changes in reservoir properties laterally, and an uncertainty on oil-water contact (OWC) levels along the trajectories. The key inputs for optimal well placement of the two branches were measurements to map the reservoir top while drilling and the OWC up to approximately 20 - 30m TVD from the wellbore. Before deploying the ultra-deep directional resistivity tool, it was critical before drilling to evaluate how top reservoir and OWC would be mapped by inversion of electromagnetic measurements. The reservoir conditions were challenging with a low resistivity contrast towards reservoir top and a gradually changing resistivity towards the OWC. It was, therefore, critical in the pre-job phase to help all involved in the future geosteering operation to get familiar with using the ultra-deep resistivity real-time interpretation to meet the objectives and to update the geomodel after drilling. To plan the well placement job a new workflow was applied to build a realistic geomodel based on geological understanding, legacy offset wells measurements, and seismic interpretations. Then potential scenarios generated from this geomodel were used to simulate synthetic ultra-deep directional resistivity responses and inversions results, synthetic standard LWD-data, and seismic. Finally, an updated geomodel was built after the drilling campaign, validated through "Model-Compare-Update" traditional iterative process using synthetic and real data. In conclusion, the pre-job analysis was important to understand how to interpret reservoir top and OWC. This knowledge was used in real-time while drilling and post-operation to update reservoir top interpretation and the OWC position. This case study describes the importance of having a workflow to build a realistic high resolution geomodel that is validated with all the subsurface measurements at different scales. Deployment of such highly integrated workflow open new horizon for the collaboration between service company and operator for improved pre-job planning, real-time decisions and post-job integrated interpretation. Furthermore, integrated interpretation of data from the two wells with seismic performed over the post drilling analysis is proven to be essential to ensure future production steering of the two-branched horizontal producers. An alternative ultra-deep azimuthal resistivity inversion algorithm was successfully used while drilling along with the standard inversion to better interpret reservoir top in the context of low resistivity contrast from this case study. An important, and unprecedented effort of pre-job planning was conducted to select optimal LWD real time dataset required. IT and "cross-platform-data-exchange" challenges were overcome to allow an extensive and innovative use of realistic geomodel scenarii for multiple measurements simulation, including from synthetic ultra-deep resistivity inversions results, standard LWD-data, to seismic interpretation.

Abstract In this case study, we present the use of a new look-ahead resistivity technology to solve a challenge on the Valemon field where the top of the reservoir could not be mapped from surface seismic. The objective was to extend the overburden section deep enough to secure sufficient formation strength at the casing shoe while eliminating the risk of accidental drilling into the reservoir below. The application of the new technology secured standard casing design, and eliminated the extra time and costs associated with implementation of the managed pressure drilling technique. The target was to extend the 12 ¼-in overburden section 10-15m TVD into the Viking Group, as this formation generally provides sufficient formation strength for the 9 7/8-in casing shoe to enable conventional drilling of the following reservoir section. As there was a risk that the Viking Group could be absent or very thin in this area of the Valemon field, the look ahead measurement was used to monitor the formations ahead of the bit while drilling. Detection of higher resistivity ahead of the bit indicating an approaching reservoir would enable stopping prior to drilling into it. No reservoir response was detected ahead of the bit, and this enabled a safe extension of the 12 ¼-in section into the Viking Group as per the objective.

Deep directional electromagnetic (EM) logging-while-drilling technology is the principal enabler of proactive well placement. The reservoir-scale measurements are used to map boundaries and fluid contacts more than 30 m away from the wellbore and to optimize well placement in increasingly more-complex scenarios. As the drilling progresses, deep directional resistivity (DDR) data are continuously inverted to estimate a 1D formation resistivity pro le locally, and the inversion results are stacked to create a 2D reservoir map. This approach is adequate if the formation is layered and slowly varying laterally. However, in complex reservoir scenarios with locally 2D or 3D structures or where the formation changes abruptly, the 1D approximation used in real-time inversion may not be the most accurate solution. We introduce a new, minimally biased pixel-based inversion to accurately map 2D complex reservoir structures. The inversion uses a 2.5D EM simulator, makes no assumption about the reservoir model, and is able to image non-1D geological structures, such as faults, sand injectites, shale lenses, and other complex geometries with arbitrary anisotropic resistivity distributions. An adaptive regularization ensures that the most plausible resistivity distribution with the least resistivity variation, consistent with the data, is found. The algorithm is parallelized to run on a cluster and is feasible for real-time application, provided relatively moderate computational resources are available. The new reservoir maps derived from the 2D inversion enable more quantitative and informed well-placement decisions, deliver detailed insight about the reservoir structure, and allow a precise re nement of existing reservoir models.

An inversion-based interpretation workflow is developed to determine individual thicknesses of multiple nested casings using induction-based multispacing and mutifrequency measurements. it includes an inversion-based channel calibration to determine unknown casing permeabilities and conductivities while the presence of casing eccentering is indicated by a QC flag. The inversion-derived data covariance matrix provides the uncertainty estimates in the inverted casing thicknesses. The derived data resolution matrix reveals the measurement information content which has helped in optimizing the importance of each channel in multifrequency data and in defining measurement accuracy for required casing thickness resolution. The proposed workflow is capable of handling an arbitrary number of nested casings and has been validated on synthetic and field data sets.

A pixel-based inversion approach is introduced for interpretation of deep directional resistivity logging-while-drilling electromagnetic measurements. It can be used for real-time reservoir mapping while drilling to accurately place the wellwith respect to reservoir boundaries and fluid contacts as well as for reservoir characterization in high angle and horizontal wells. The methodology is based on the Gauss-Newton approach, using an adaptive l1-norm regularization and a robust error term to determine the 1D formation anisotropic resistivity profile and local formation dip. The new inversion allows high-resolution imaging of the subsurface resistivity distributions and consistent integration of measurements of different depth of investigation. To further enhance the robustness and accuracy of the subsurface images, a fast approximate 2-D inversion is developed, which uses approximate modeling based on locally 1-D models, resulting in reservoir images of improved accuracy and consistency in mildly 2-D and 3-D scenarios. The inversion's ability to generate a stable robust but detailed resistivity image of the formation near the wellbore is proven on synthetic and field data.

An inversion-based workflow has been developed for resistivity anisotropy and formation dip evaluation using deep directional resistivity and conventional array resistivity measurements in vertical and deviated wells with inclinations up to 60°. The inverted anisotropic resistivity profile can be used in reservoir characterization, to identify low resistivity pay, large scale formation dips, and to aid in refining the model of the overburden thereby improving Controlled Source Electromagnetic measurement interpretation. The workflow includes inversion-based calibration of harmonic resistivity responses. The measurements are processed in a parallel multi-step workflow based on parameter sensitivities to avoid noise propagation into less sensitive parameters. The workflow is validated on synthetic anisotropic Oklahoma formation models for a range of inclination angles from 0° to 60°. Furthermore, the processing of field data from a vertical well has shown very good agreement with the wireline triaxial induction-derived anisotropic resistivity profile acquired in a nearby well. Presentation Date: Wednesday, September 27, 2017 Start Time: 3:05 PM Location: 330A Presentation Type: ORAL