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Seismic-While-Drilling – A Technological Breakthrough for Optimized Drilling Risk

Wednesday, 18 November 2015 14:58 Written by 

Seismic-while-drilling is a niche technique of using drill bit noise as a source for acquiring real time vertical seismic profile of the onshore and offshore wells through receivers laid out along the ground or seabed. Over the last two decades, this technique has attracted many operators exploring geological complex areas.

The main advantage of this technique is that it allows the geoscientists to improve the time-depth conversion of sub-surface geological information in real-time while drilling. Thus, drillers can be guided with high confidence in many critical situations like casing point selection, evaluating drilling hazards, identifying high pressure zone etc. Seismic while drilling technique helps operators save costs and reduce risks by capturing seismic data without interrupting drilling operations.

The figure on the left, seismica seismic profile along the horizontal well is generated real-time while drilling and correlation is being made with previously acquired 3d seismic data. The figure on the right hand displays a vertical seismic profile created using seismic-while-drilling technology in a vertical well.

Technological Shift in Seismic-While-Drilling:

In the early implementation of Seismic While Drilling, roller-cone bits served as the source of the downhole seismic energy. Use of a roller-cone bit as a seismic source has several proven applications and advantages in seismic-while-drilling techniques including:

  • Real-drill-time velocity check shot information.
  • Guiding the bit to a target as seen on surface-acquired seismic data.
  • Real-drill-time imaging ahead of the bit.
  • Real-drill-time depth-to-time conversion to know when the bit is reaching an important depth interval.
  • Positioning the bit at the top of an interval that needs to be cored.

With the current technological advancement, seismic-while-drilling (SWD) data can be acquired by embedding seismic sensors in the drill string near the drill bit. Now vertical seismic profile (VSP) data can be acquired while drilling with any kind of bit, including PDC bits, by using these downhole sensors together with a surface-based seismic source. At each depth, where seismic information needs to be obtained, drilling action must cease for several minutes so that the downhole sensors are in a quiet environment as they record the seismic wave field produced by the source. This downhole seismic sensor technology allows numerous seismic applications to be implemented as the well is being drilled, such as (a) Predicting overpressure intervals; (b) Imaging below and laterally away from the well bore; (c) Defining the relationship between drilling depth and seismic image time; (d) Guiding the bit to a target identified on a surface-based seismic image.

Seismic while drilling is deployed almost exclusively for all deep water or highly deviated/horizontal wells. This technique holds big potential in unconventional resource development. One of the key elements of successful implementation of seismic-while-drilling is data processing and accurate interpretation. As the technology is applied in real-time while drilling the well, it is very crucial to complete processing and interpretation of seismic-while-data ion a timely manner without adding any rig idle time. In general, a team of experts comprising seismic data processors, interpreters and geologists work closely 24/7 while drilling activities are going on.

For more information and implementation of seismic-while-drilling in Geological complex reservoir, please contact iOG solutions.

Last modified on Friday, 04 November 2016 12:02
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