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Seismic MWD

Drilling in time, on time, it's about time

Schlumberger, Sugar Land, Texas, USA

Corresponding author: esmersoy@sugar-land.oilfield.slb.com

The first 20% of the full text of this article appears below.

Since the dawn of logging-while-drilling (LWD) in the 1980s, the industry has wanted a reliable while-drilling borehole seismic measurement. However, a number of technical roadblocks prohibited its realization until recently. These difficulties included the nature and required accuracy of the measurement, timing issues, sensors, automation, and the lack of an electrical connection between the downhole tools and the surface in a while-drilling configuration.

Technological solutions to these roadblocks have since been found, and today seismic MWD (seismic measurement-while-drilling) tools acquire and transmit seismic data in real time during the drilling process, without interfering with normal rig operations and without loss of rig time.

In high-cost or high-risk environments, particularly including those with significant seismic uncertainties, this technology can positively impact the cost of exploration and development drilling. Seismic MWD data is delivered in real time, so it can be used to make critical decisions while a well is being drilled. It also saves rig time by replacing intermediate wireline check-shot surveys and thus eliminates the need to stop the drilling process and pull drilling equipment out of the hole for the duration of a survey.

This technology has proven beneficial in a range of applications and some drillers are becoming accustomed to the frequently updated "bit-on-seismic" displays that it provides. The following examples of this technology demonstrate how it is being used to significantly reduce risk and uncertainty, enabling better decision-making during well construction operations and directly impacting drilling costs in the high-risk, high-uncertainty sphere of operations.

	Check-shot and velocity data in real time

 
Check-shot surveys provide direct measurements of seismic traveltimes from the surface to survey positions along the well trajectory and thus can be used to calibrate the depth scale of a surface seismic image at these positions. Real-time seismic traveltimes (check shots), in combination with survey data, are used to plot and track the . . . [Full Text of this Article]