Maximizing Reservoir Contact in the Oseberg Field Using a New Azimuthal Deep Reading Technology

Abstract

Abstract The industry today is challenged to maximize recovery from existing assets, meaning that increasingly complex and thin reservoirs must be drilled and evaluated. Consequently, reservoir management efforts aimed at maximizing production through optimal wellbore placement require increasingly sophisticated geosteering and formation evaluation capabilities. This paper discusses the use of a newly deployed azimuthal, deep-reading, resistivity tool for geosteering and formation evaluation while drilling in the Oseberg Field. This tool, combined with well steering software, gave geosteering engineers the ability to steer the well not only on variations in resistivity but on direct measurements of resistivity that delineated layer boundaries and provided early warning of approaching bed boundaries. This system created a complete picture of the layers above, below, and around the sensor. A complete picture improved our understanding of the reservoir's geology and aided us in placing the well in thin sand. It also improved the capability to steer the well through the most productive part of the reservoir while maintaining a desired distance from adjacent formations. In addition to geosteering and well placement, advanced application algorithms developed for this tool are used to calculate formation resistivity and formation anisotropy, as well as dip and azimuth of formations within and around the reservoir. This paper describes the planning and execution of the geosteering job done with this new technology. A flowchart of the geosteering workflow is discussed. Formation evaluation and well placement techniques based on this new azimuthal deepreading technology are explained and detailed. Lessons learned, pitfalls to avoid, and best practices and challenges are described in detail. Finally, field examples are included that show the usefulness of this new technology during steering and evaluating the Oseberg field. Introduction With oil discoveries in decline, the industry today is challenged to maximize recovery from existing assets; consequently, reservoir management efforts aimed at maximizing production through optimal wellbore placement require increasingly sophisticated geosteering and formation evaluation capabilities. Drilling through complex reservoirs with traditional technology is difficult since pre-well geological models are often limited by the resolution of seismic data. Even with nearby offset wells against which to correlate, complex geology by definition has significant variations that cannot be fully anticipated before drilling. Effective schemes for reservoir drainage to maximize net recovery revolve around increased production, optimized production, reduced cost, better reserve estimates, and access to more reserves. The means to accomplish this objective is two-fold:improve reservoir understanding andcreate effective schemes for reservoir drainage to maximize net recovery by maximizing contact with the hydrocarbon-bearing reservoir. A new azimuthal, deep resistivity logging-while-drilling sensor accomplishes this objective. The tool is designed to combine deep reading azimuthal (directional) measurements with petrophysical interpretation capabilities in a two-in-one geosteering/formation evaluation service. The azimuthal deep resistivity tool provides a deep reading azimuthal (directional) service that greatly enhances geosteering and gives significantly greater well control over placement when drilling horizontal wells. The system also provides important petrophysical parameters such as the horizontal resistivity, Rh, the vertical resistivity, Rv, and the relative dip angle.