Best Practices for Using Azimuthal Geosteering Technology in the Gulf of Mexico
Hanming Wang, Heather Bedle, Abigail Hymel, Soazig Leveque, and C. Winston Wheeler
One of today's challenges is to maximize recovery from existing assets, which may require drilling horizontal wells in complex and thin reservoirs. Optimal well placement is the key technology to achieve this objective. In the past 15 years, the most effective and widely accepted technologies are borehole images (such as density, Gamma and shallow resistivity) which can determine when the well path has left the reservoir, and the angle of exit. By taking the appropriate corrective angle, the well path can be adjusted to re-enter the producing zone. The limitation of such geological steering is the relatively small volume of investigation of image sensors which results in suboptimal well path. This paper discusses recent developments in azimuthal LWD resistivity measurements, which have much larger depth of investigation than image-based sensors and deliver an estimate of the distance to bed boundary (D2B) to predict the position of reservoir roof or floor. The technology makes it possible to steer the well within the reservoir and place the well in the best location. The hidden assumption of this data processing is the local geological structure, approximately 10- 20 ft around the well path, which can be simplified to a 2 or 3-layer 1-D model. Any deviation from these favorable conditions may cause uncertainty on D2B and hence effect the geosteering decision. In order to properly use the new technology, the operating envelope must be addressed. This paper describes some lessons learned, pitfalls to avoid, best practices and challenges based on the analysis of data acquired on the GOM shelf.
AAPG Search and Discovery Article #90167©2013 GCAGS and GCSSEPM 63rd Annual Convention, New Orleans, Louisiana, October 6-8, 2013