Seismic While Drilling for Enhanced Look-Ahead-of-Bit Capabilities - Case Study of Successful Mud Pulse Coupling Demonstration
A. Judzis, SPE, TerraTek, T.S. Green, Idaho National Engineering and Environmental Laboratory, G.M. Hoversten, Lawrence Berkeley National Laboratory, and A.D. Black, SPE, TerraTek
This paper for presented at the 2000 SPE Annual Technical Conference and Exhibitionin Dallas, Texas, 1-4 October 2000,
Copyright 2000, Society of Petroleum Engineers Inc..
Abstract
Accurate prediction of formation pressures (pore pressures) is critical
to conduct safe and economic drilling operations. This information
is essential for both optimizing casing and drilling fluid programs,
and is vital in avoiding well control problems. Seismic while drilling
techniques offer improved safety and drilling performance for areas
where uncertainties exist in formation tops and prediction of over-pressured
zones. Examples of potential economic benefit include elimination of
casing strings, maintenance of optimum hole size to total depth, and
reduction of non-productive time. There are currently no systems that
reliably provide this capability.
This paper presents the results of an ongoing development program designed
to improve the efficiency and safety of drilling operations through the
development of a down hole seismic source for enhanced 'look-ahead-of-the-bit'
capabilities while drilling. The program is funded in part through the
US Department of Energy. Results obtained from innovative large-scale
tests show the effects of a down hole seismic source utilizing the hydraulic
force of a mud pulse generated through a flow interruption device. Three
axis accelerometers embedded in rock samples in a simulated wellbore
environment showed signal responses which are under review in anticipation
of analyzing 'look-ahead-of-bit' requirements.
The results provide a unique opportunity to examine seismic wave propagation
in samples shorter than a wavelength and the potential to benchmark seismic
sources for coupling efficiency before deploying tools in an expensive
offshore environment. For offshore operations, the ability to improve
pore pressure predictions ahead of the bit is one key to success.
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