Abstract

Vibration measurement while drilling is very important. Real-time analysis of the vibration data can be used to evaluate the performance of the downhole tools and to identify the rocks. The paper briefly introduced the work principles, composition and application of the system.

The system is composed of near-bit vibration measurement tool, surface vibration detecting device, wireless transmitting system, signal processing and indicating software system. The downhole measurement system detects and processes the near-bit data, the result is sent to surface in real time, then operators can change drilling parameters in time if harmful downhole conditions are indicated, considering with the surface measurement.

This system has been extensively tested and proved to be effective in identifying the difference of breaking fossil coal and other rocks. Detail of the test and the method will be discussed in the paper. Especially in CBM drilling, the conventional electromagnetic resistivity or gamma measurement while drilling system mounts far away from the bit(more than 7m), however the ROP of CBM drilling is usually high, which lead to time lag and large deviation of trajectory. The use of near-bit and surface vibration measurement while drilling system can identify the seam top or floor as quickly as the bit contact the boundary, to increase drilling efficiency.

With the vibration measurement while drilling tool, the drilling efficiency can be remarkably improved. This paper will highlight the technical development and present helpful case histories and recommendations.

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