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.

Following the Gulf of Mexico Deepwater drilling moratorium in 2010, the industry focus towards well integrity assurance has significantly increased. Several new and updated regulations and best practices have been published in the last two years, including API Standard 65 -Part 2 and API RP 96. These two industry accepted standards highlighted that determining the hole volume to confirm the cement slurry volume, to fill-up the annulus to the designed top of cement, is one of the many factors impacting cement placement success during well construction process.A new solution for riserless section was developed based on existing Logging While Drilling (LWD) electromagnetic propagation resistivity measurements, which meets the requirement to understand hole volume drilled with water based mud in deepwater environment.Historically, deriving an accurate caliper from LWD electromagnetic propagation resistivity measurements has never been easy due to big uncertainty of mud resistivity (Li et al, 2003). The implementation of a novel simultaneous inversion model and forward modeling database from standard 2-Mhz propagation resistivity, for water-based mud (WBM) and large boreholes, provided the solution to overcome that uncertainty (Whyte et al, 2012).This novel solution was specifically developed to address the needs for the riserless top-hole sections of high cost deepwater wells: from cement volume calculations, identification of borehole degradation through time, and new opportunities for identification of shallow water flows using the full capacity from the inversion process.The extensive validation of this innovative approach with wireline mechanical calipers in numerous hole sections resulted in far better results than initially anticipated (Whyte et al, 2012). The information obtained provided significant insights into the reliability and limitations of the current algorithm. The ability to monitor the borehole size while drilling, as well as analyzing the reaming and trip out passes from recorded data, makes this measurement a valuable source of time-lapse information. The next validation process consisted in the comparison between cement volumes computed using these measurements against identification of cement returns during riserless cementing operations in deepwater wells.The LWD caliper derived from propagation resistivity measurement was analyzed in more than a dozen of wells in Gulf of Mexico. Spefic case studies covering the drilling and cementing operations are presented in this paper.

Deep directional resistivity LWD measurements have been shown to be sensitive to resistive transitions over a broad range of distances around the tool from tens to hundreds of feet. These detected transitional surfaces are primarily used to detect formation resistivity boundaries and assist with mapping geological profiles. The inverted formation dip and vertical resistivities are also resolved in the same search space. While the formation dip is used in conjunction with the reservoir-mapping interpretation results, the vertical resistivity, specifically the vertical and horizontal resistivity ratio, or anisotropy, has not received the same amount of attention. Resistivity anisotropy is useful when calculating the formation resistivity in layered formations, as conventional resistivity tools measure the resistivity in one direction, which is perpendicular to the tool axis. With conventional induction and propagation resistivity tools, the electrical current preferentially transits the conductive lithologies, resulting in an apparent resistivity measurement that does not represent the true sand resistivity. The petrophysical evaluation often results in an apparent high-water saturation, which can result in incorrect decisions to abandon a prospect. To understand two new fields located onshore Alaska, three horizontal appraisal wells were drilled with deep directional resistivity LWD technology. While the primary goal was to characterize the lateral resistivity profile and bed boundaries away from the wellbore, accurate water saturation calculations along the horizontal section are critical for making appropriate development decisions. A review on how and why deep directional resistivity LWD technology is sensitive to anisotropy and how anisotropy is derived from parametric inversions is presented with a comparison between deep directional resistivity LWD measurements, 3D petrophysical modeling of propagation, and offset well triaxial induction anisotropy measurements. Integrating 3D petrophysical processing and triaxial-induction technology into deep directional resistivity LWD measurements add to the strength of the anisotropy output. The comparison shows that deep directional resistivity LWD measurements can be used independently to give accurate anisotropy results. The result of this process provides a corrected resistivity measurement of vertical and horizontal resistivity in anisotropic formations for petrophysical models. Use of the corrected resistivity as a true resistivity (Rt) input for water saturation will ultimately drive better development decisions.

Recently the drilling industry has seen many advances in the application of deep directional electromagnetic (EM) measurements for mapping deeper into the reservoir, with the latest one capable of seeing over 250 ft above and below the wellbore providing unprecedented understanding of the reservoir. This measurement technology is now being used to look ahead of bit while drilling, for exploration wells to reduce drilling risks associated with unexpectedly penetrating certain formation. With the increasing complexity of the reservoirs that the industry is targeting, there is more and more quest for expanding the reservoir mapping capability, not just a 1D approach that can only map resistive boundaries on the vertical axis or near vertical axis and assume infinite extend in all other directions, but to enable geoscientists to better steer the well and better understand the reservoir structure and fluid contact in a full three-dimensional context around the wellbore. In this communication, the authors introduce a new solution to this quest for full three-dimensional real-time reservoir mapping. The solution is composed of three parts: a set of new measurements acquired downhole and transmitted to surface in real-time, a new inversion algorithm that is model independent and therefore fit for any reservoir complexity, and a new computing paradigm that make it possible to provide answers in real-time while drilling. The new set of measurements almost doubles the number of well logs that were acquired before and greatly enriches formations evaluation around the wellbore. The new algorithm, different from all previous algorithms, is not confined to any specific forms of models, making it suitable for exploring and finding solutions in complex reservoir settings. Finally, taking advantage of the latest advances in the Cloud computing, turnaround time of the new inversion is improved by over hundred times, thanks to the scalability of the algorithm design and Cloud computing infrastructure. Combining all these together allows to achieve three-dimensional reservoir map, without having to tradeoff between high resolution and depth of investigation. The 3D reservoir map that is generated from multiple transverse 2D inversion slices in real-time, enables timely update of reservoir model as drilling progress for the operator to make informed decisions. This new technology is currently deployed in several locations around the world and in different environments. In this paper, the authors review deployment results, to illustrate the technology, from preparation to real-time execution, and finally to post-job model update. With the ability of mapping in all directions while drilling, this technology opens the door to many applications and will enable the operators to target more complex reservoirs and achieving better geosteering results where 3D mapping and steering are required. In addition to its benefits for real-time operations, the technology also enables the geoscientists to update and calibrate their reservoir models with fine and accurate details, which can further benefit multiple disciplines including drilling, completion, production and reservoir management.

Reservoirs in the Northern Gulf of Mexico (NGOM) are predominantly drilled with low angle wells. Drilling a well horizontally presents its own set of challenges.The Mississippi Canyon block 22/21 operated by ANKOR Energy embodies the significant drilling challenges sometimes found in the NGOM reservoirs. The ЉH SandЉ reservoir is a low resistivity (3 to 5 ohm.m) reservoir bounded by a northeast southwest fault. The overburden is uniform for more than 200ft TVD above the reservoir, making the landing challenging with conventional well placement techniques. The operator was planning a 2200ft lateral section to be drilled close to the Gas Oil Contact (GOC). Early water production was observed in the offset well located at the toe of the planned well, questioning the current position of the Oil Water Contact (OWC). Landing this well is challenging from both a geological and drilling point of view as a 3D trajectory is required to avoid the fault and offset wells.In light of these challenges, the operator decided to use the very-deep electromagnetic (EM) directional resistivity tool with its detection range of more than 100ft, enabling the detection of the top of the H sand reservoir long before landing. In the lateral section, the tool was used in conjunction with an integrated petrophysical platform to map the top of the reservoir, detect the OWC and identify the lithology and fluids present while drilling.While landing the well, the top of the H sand reservoir was detected 48ft TVD away -10ft deeper than expected. The very-deep directional resistivity tool enabled the well to be confidently landed despite the lack of correlation markers and depth uncertainty of the ЉH SandЉ reservoir. The OWC was detected more than 70ft below the well during the landing section even though the bit had not penetrated the H sand reservoir yet. The top of the reservoir and the OWC were mapped throughout the length of the lateral section along with the lithology and fluid content. Towards the toe of the lateral section, near a producing offset well, the OWC, still 50ft below the current trajectory, was observed to be rising up and getting closer to the well. Total Depth (TD) was called early to avoid premature water production. Water coning was confirmed as the reason behind early water production in the offset well.The use of this technology during the landing and the lateral section of the well reduced dramatically the risk associated with geological uncertainty as well as fluid contact position providing critical information for field management planning.