GB1131892A - Method and apparatus for measuring changes in borehole fluid pressures - Google Patents

Abstract

1,131,892. Pressure gauges. ESSO PRODUCTION RESEARCH CO. Feb. 3,1966, No. 4815/66. Headings G1L and G1N. Apparatus for measuring changes in ambient pressure, particularly in bore holes, comprises a source of fluid at a reference pressure, means for varying the fluid content of the reference source to eliminate any pressure differential between the source and the ambient and means to measure the variation of fluid content to determine the change in ambient pressure. In Fig. 1, the means for detecting the pressure differential comprises a capillary tube 13 containing opaque and transparent fluids with interface 36, connected respectively to bellows 15 and reference pressure cell 10. Bellows 15 may be situated in the bore hole and any change in pressure results in movement of the interface which controls the incidence of light on the photoelectric cells 21, 22 which control reversible motor driven pump 24 to increase (or decrease) the supply of liquid in the reference cell system to restore the interface to its original position. Valves 31, 32 and 33, 34 operate alternatively so that the pump may operate continuously to increase (or decrease) the fluid content of the reference source. The position and number of strokes of the pump is electrically recorded to indicate the amount of fluid-flow needed to restore equilibium and therefore the change in pressure experienced by bellows 15. In an alternative embodiment, Fig. 5 (not shown) the pressure differential is indicated by a liquid-gas interface in a meniscus forming tube. In a third embodiment Fig. 6 (not shown) a transducer sonde is used to detect differential pressure changes, the sonde output controlling the quantity of gas in the reference source by means of valves leading to either a source of higher pressure gas or to an exhaust.