Real Time Proactive Optimal Well Placement using Geosignal and Deep Images
Authors: Bittar Michael S. , Chemali Roland E. , Pitcher Jason L. , Cook Robert , Knutson Craig 
Published: July 2010

Modern oil field drilling operations through complex reservoirs can be extremely challenging because geological models are often limited to the resolution of seismic data. Often, these reservoirs have significant variations that cannot be fully anticipated before drilling. Efforts toward maximizing production from these complex reservoirs through optimal well placement require increasingly sophisticated geosteering and formation evaluation capabilities.

Advances in directional logging-while-drilling (LWD) resistivity measurements improved real-time geosteering by providing discrete azimuthal measurements, deep images, and distance to the formations from above, below, and to the side of the sensor while drilling horizontally or at high-inclination angles through the reservoir. Distance-to-bed boundaries calculation is achieved by means of the geosignal, a new geosteering signal. Derived in real time, the geosignal is azimuthally sensitive and strongly dependent on the distances to boundaries.

These novel measurements, combined with well steering software, enable geosteering engineers to steer the well not only on resistivity variations but also on direct deep resistivity images and on azimuthal geosignal. Boundaries are identified as they approach the well from above, below, and any direction around the sensor. A complete picture improves the understanding of the reservoir's geology and aids in placing the well in thin reservoirs. It also improves the capability of steering the well through the most productive part of the reservoir while maintaining a desired distance from adjacent formations.

This paper describes the planning and execution of a typical well placement operation accomplished with this new technology. New interpretation methods specific to deep images are illustrated on real data and many examples are shown. The paper also provides details about the workflow of geosteering based on this new azimuthal deep-reading technology and discusses the benefits and limitations, lessons learned, pitfalls, and best practices. Finally, field examples from around the world are included to show the usefulness of this new technology for well placement and formation evaluation in various types of hydrocarbon reservoirs.

Introduction

The oil and gas exploration and production industry is increasingly migrating to high-angle wells, especially in offshore operations. The partial departure from vertical wells began in the 1980s and has accelerated in recent years because the technological advances have made it easier and less risky to drill extended reach wells in many types of reservoirs. There are multiple advantages of high-angle wells and horizontal wells. A horizontal well generally yields the same initial production as that of several vertical wells combined, which significantly reduces the surface infrastructure requirements. In an offshore field development, a single platform can launch multiple high-angle wells in many directions, covering vast areas that would otherwise require multiple platforms with vertical wells. During the life of the field, if properly placed, horizontal wells enable a more efficient sweep of the producible hydrocarbon than vertical wells, leading to higher volumes of ultimate oil and gas recovery. In addition to cost savings and increased revenue, horizontal wells offer a reduced footprint for a given hydrocarbon production, significantly reducing the effect on the environment.