| 摘要 |
<p>Improved systems, apparatus and methods for measuring downhole parameters in a well being drilled in the earth with apparatus comprising a drill string, a mud pump for circulating drilling fluid, and flow restriction means located near the bottom of the string so as to cause a pressure drop between the restriction means and the borehole annulus that surrounds the drill string. In accordance with one aspect of the invention, the improvements involve downhole pulser means for generating negative mud pressure pulses which are utilized to transmit information concerning downhole parameters to above ground equipment. The improved downhole pulser means utilizes valve means to bypass the restriction means in a manner that results in the efficient generation of effective pulses with minimum expenditure of electric energy. In accordance with another aspect of the invention, improved structure is provided for housing the pulser means and for accommodating associated downhole apparatus. In accordance with another aspect of the invention, improved methods are provided for extracting negative mud pressure pulse signals from interfering signals resulting from mud pressure variations due to the mud pump means. In accordance with a further aspect of the invention, improved direct current downhole power supplies are provided.</p> |
