Using MSE and Downhole Drilling Dynamics in Achieving a New World-Class Record in an Extended-Reach Drilling Well, Offshore Abu Dhabi
Authors: Abbas Nashat , Al Nokhatha Jamal , Salgado Luis , Zakaria Rafik , Fares Wael , Aki Ahmet 
Published: November 2020

The process of drilling a successful extended-reach well often involves addressing many geological challenges. Some of these challenges are due to uncertainty in the structure model along the horizontal section as well as the lateral changes in the reservoir properties, from heel to toe of the well. This uncertainty may affect the borehole tortuosity as well as reduce the reservoir contact. It is clearly observed that approaching the less-porous boundaries causes undesired borehole azimuth swings.

Often, the need to drill complex or challenging ERD wells efficiently,contrasts with geological aspects of data requirement and transmittal, reactive geosteering response times and accuracy of well placement. This may often require non-unique approaches in Middle East carbonate reservoirs when considering stacked sequences of reservoirs with different properties / net pay thickness; different top- and bottom-seal lithological units, and zones with limited markers requiring stringent well placement.

The objective of this paper is to illustrate that by assessing the details of reservoir geology and key operational markers relevant for best practices, drilling approaches can be customized for each reservoir or scenario: for example, defining drilling ROP windows on a per-target layer basis.

A well-placement methodology and workflow were developed and integrated with the calculated mechanical specific energy (MSE). The MSE is calculated using both surface drilling parameters and downhole drilling dynamics data from the drilling downhole optimization collar. The methodology also includes an optimized bottom hole assembly (BHA) design with azimuthal density image and a point-the-bit rotary steerable system (RSS) to geosteer the well within a thin target layer. This occurs while maintaining the planned target trajectory with a minimum borehole tortuosity using real-time drilling optimization.

The understanding of the target layers with the analysis of the historic offset horizontal wells resulted in the delivery of engineered solutions to mitigate the uncertainty in the geological challenges.The MSE along with the downhole drilling dynamics data from the drilling downhole optimization collar has shown good correlation with real-time logging-while-drilling data and can help in making quick real-time geosteering decisions.It was reliable in determining the change in the stratigraphic movement of the well trajectory along the horizontal section. In addition, using the drilling downhole optimization collar effectively can assist in anticipating any approach to different porosity boundaries that help to reduce or eliminate the undesired borehole azimuth swings.

As a result, the downhole vibrations are also mitigated and constantly remain within the allowed limits using downhole measurements for torque at bit and weight on bit.This study has shown outstanding and promising results for the potential value added when using the MSE along with the downhole drilling dynamics data in a proactive geosteering technique for a geosteering/geostopping portfolio.

The uniqueness of the integration of the MSE and real-time geosteering geological model lies in its ability to address the geological challenges, enhance the drilling process, and maximize the asset value in the reservoir field of this study.Further study is needed to include different reservoirs to validate the concept.