GB799602A - Improvements relating to the measurement of liquid levels in wells - Google Patents

Abstract

799,602. Echo-sounding and distance-measuring apparatus. BRITISH PETROLEUM CO., Ltd., BOOTH, S. E., and WARD, E. H. May 26, 1954 [July 2, 1953], No. 18376/53. Class 118 (2). Apparatus for measuring and recording the level of liquid in a well comprises a resilient diaphragm made, for example, of rubber and secured across a resonant chamber which is adapted to communicate with the well in such manner that when the diaphragm is made to vibrate a low-frequency sound wave is sent down the well, and a sound detector comprising a microphone connected to amplifying and recording means. The main feature of the invention is a generator of low-frequency sound waves, e.g. less than 50 c/s., since higher frequencies are greatly attenuated in wells, e.g. oil wells, especially those containing obstacles such as tubing and insulators. Any conventional amplifier and recording means may be used but the microphone must be sensitive to low frequencies and hot-wire microphone is therefore preferred. This is combined with the generator in the embodiment of Fig. 1, wherein a circular, domed rubber diaphragm 10 is secured over the open end of a cylindrical chamber 12 by means of a beading 11 compressed between ring 14 and flange 15. The chamber 12 is about 8 inches in diameter and 3 inches deep and has a central aperture 17 about 1¢ inches diameter, in the base. This connects with a tube 18 carrying a hot-wire microphone element 23 and having at its lower end an adapter 19 which plugs into a socket in the well head. A cylindrical tube closed at its upper end and having holes in its side wall is welded. to a bush 22 which connects the adapter 19 to the tube 18 and forms a damping filter 21. A wing union 28 provides easy access to the microphone 23. The circuit of a suitable amplifier having filter networks to selectively reduce the top cut-off frequency is disclosed (Figs. 2 and 3, not shown). A push-button switch is provided to materially reduce the gain of the amplifier while the diaphragm 10 is struck by the hand so that the initial signal may be attenuated and the amplifier returned to full gain in time to receive the echo. Typical recorder traces obtained from oil wells and a water well are reproduced in Fig. 4 (not shown). The embodiment shown can only be used on wells producing little or no gas pressure at the surface. For wells producing a high gas pressure a modified construction (Fig. 5, not shown) is used. In this a further chamber is provided above the rubber diaphragm, the latter having a small hole to equalize the quiescent pressures on the two sides. A rod connected to the diaphragm and passing through sealed glands in both chambers has a domed head to serve as a striking means.