--> Abstract: Understanding Horizontal Well Logs to Improve the Geological Model While Drilling; #90063 (2007)

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Understanding Horizontal Well Logs to Improve the Geological Model While Drilling

 

Thorsen, Arve K.1, Jeremy C. "Jez" Lofts2, Trond Gravem3, Knut J. Rønning4, Andrew J. Holden4 (1) Baker Hughes INTEQ, 5020 Bergen, Norway (2) Baker Hughes INTEQ, Houston, TX (3) Baker Hughes INTEQ, 4056 Tananger, Norway (4) Norsk Hydro ASA, 5020 Bergen, Norway

 

During horizontal drilling it is important to understand the structural geology of the reservoir, i.e. the 3D development of the structure drilled.

The geological model plays a significant role in horizontal drilling as it is the foundation of any horizontal well placement planning. However, during drilling the geological model has to be calibrated against the actual formation data recorded, in order to assist in corrective actions needed to keep the drill bit within the desired reservoir zones.

To understand the local geological structures during drilling, image data display and interpretation are done in real time to better resolve the structural dip and strike attitudes of the larger structures in the geo-model.

 

Resistivity logs can be used to reveal the geology further away from the wellbore. Measurements reading up to 15 m around the wellbore can be obtained if the environment is favorable. By combining all the different measurements and use enhanced modeling capabilities to interpret the horizontal log responses, the well logs can be used to perform several estimates, like the distance to approaching layers, the true dip and strike of the formation, warnings prior to exiting the reservoir, distance to the Oil-Water Contact, etc. By tying the data to the geological model these estimates can be applied to make plausible predictions of the geology ahead of the bit and hence significantly aid the geosteering of the well within the reservoir.

 

This paper shows two examples from horizontal wells drilled in distinctly different reservoirs, applying the techniques described above. The combined use of horizontal well logs and the specific geological model gives another dimension to the real time wellbore placement, and hence to the economics of the well.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California