OPTICAL PROBES

摘要

After an oil well has been drilled, lined and cased, and is producing, it may be desirable in situ (either at the wellhead or downhole) to measure, and log (record), the rate at which fluid, and its several distinct components, is flowing out of the geological formations through which the bore has been drilled and is passing into and up the casing. A useful type of detector system for this purpose is an optical probe (31), and the invention proposes a novel design of probe which has a doubly-angled tip, there being measured the light totally internally reflected at the interface (37), which depends on the ratio of the refractive indices of the probe tip and fluid component in which it is immersed. The invention also proposes an improved method using such a tipped probe, in which, to facilitate distinguishing between the components of a multi-phase fluid such as the gas/water/oil formation fluid in an oil well, there is employed a pair of adjacent probes, one of which is designed to distinguish between gas and liquid and the other of which is designed to distinguish between oil and "not oil" (gas/water), and there are then logically combined the outputs of the two so as to give an indication of which component the probes are in.