Most production wells currently drilled in the North Sea are in complex geological settings. In order to place the wells safely and effectively, drilling a successful production well requires an advanced technology and integrated proactive reservoir navigation approach, in addition to multiple data driven answer products from downhole tools. Extra deep azimuthal resistivity logging while drilling (LWD) tools can detect boundaries up to 30 m away from the wellbore given optimal resistivity conditions. Combined with multicomponent inversion modelling (MCWD), the data acquired are used to map multiple boundaries, individual sand bodies, reservoir thicknesses, and lateral reservoir changes. Borehole images aid in geosteering and are used to steer up or down based on structural boundaries identified on the image. Using wired pipe technology that provides telemetry rates good enough for memory-resolution data, the full resolution electrical image is available while drilling. Despite complex reservoir geometry in both external boundaries and internal sedimentary structure, it was possible to succesfully geosteer by using an integrated geosteering approach. Through MCWD inversion, it was possible to track a thin, highly resistive layer at the roof for much of the reservoir, which allowed for proactive geosteering, optimizing wellbore placement and mapping of reservoir volumes.

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSlow data acquisition rates have generally not been a problem for LWD due to moderate logging speeds while drilling. With the recent advances in drilling technology, high logging speeds impact the log quality and, in particular, the nuclear logs. When a detector passes a longer interval of rock for each acquisition period, its vertical resolution is degraded. For azimuthally sectored data, this is even more of an issue, as bedding features within a sample period get blurred.The objective of the study is to develop a methodology to optimize LWD data acquisition, enabling the E&P company to drill faster and meet its data acquisition objectives. This paper describes analytical simulations and field tests performed to optimize data acquisition for fast drilling in the Norwegian North Sea. Optimization of data acquisition is described as addressing the trade-off between low data density with accurate measurements versus high data density with less accurate measurements.Based on nuclear logs acquired in adjacent wells, bed contrasts were defined for zones of interest. Modeling was done to define the minimum acquisition time needed to detect the defined contrasts. Telemetry was designed with adequate resolution for geo-steering, thus saving bandwidth. The impact on memory data accuracy caused by faster acquisition rates was modeled to check feasibility. Field tests were performed to validate the modeling results.Real-time telemetry accuracy proved adequate and the improved data density provided better definition of bedding features versus standard setup. Memory data contained better vertical resolution, further enhancing bedding features, while maintaining the required accuracy. Understanding all end users' specific data quality requirements is key to an acceptable compromise.Applying this methodology in the planning phase for other wells ensures all stake holders' needs are considered, and aids the overall understanding of LWD acquisition limitations and highlights the possibilities.