Net pay Optimization and Improved Reservoir Mapping From Ultra-Deep Look Around LWD-measurements
Authors: Antonsen Frank , Olsen Per Atle , Stalheim Stein O. , Constable Monica Vik , Irondelle Matthieu , Cook Michael , Bjorstad Trond Rognebakke , Dupuis Christophe , Marza Philippe , Seydoux Jean , Omeragic Dzevat , Denichou Jean-Michel 
Published: December 2014

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.

Background

The willingness to invest in R&D has been a key success factor for the development of the Norwegian petroleum industry since the very beginning. Operators on the NCS have pioneered innovative technology such as horizontal drilling, time lapse seismic surveying (4D), and subsea technology. The development of horizontal drilling and multilateral wells in the thin oil rim on Troll is an example of Norwegian technological excellence, which released reserves worth more than NOK 500 bn that would otherwise have been left in the ground (Mikkelsen et al. 2005).

The development of horizontal drilling has been a key component of improved oil recovery on NCS. More than 50% of all production wells today on the NCS are highly deviated or horizontal. Global companies have used the NCS as a testing ground for new technology such as horizontal drilling and new LWD measurements to geosteer the long horizontals. Given the ability to drill with high angles there is also a considerable value in geosteering this type of wells for correct well placement with regard to formation boundaries and fluid contacts. Statoil, together with the former Hydro, has been pushing electromagnetic measurements (EM) while drilling for geosteering long horizontals with great success. Examples from Troll, Grane, Velsefrikk, Oseberg and Gullfaks fields demonstrate the added value from both non-directional and directional bed-boundary mapping tools in the past, where NCS has played a key role in development and testing of LWD EM-measurements (Iversen et al. 2003; Wiig et al. 2005; Constable et al. 2012).