| 摘要 |
Once an oil well has been drilled and is producing, it is desirable to monitor the rate at which oil or gas is being delivered. It is particularly useful to know when there is a change in a fluid's output rate, for that can indicate problems with the well. This monitoring is known as "production logging". Prior to the introduction of horizontal well drilling, most wells were either vertical or only slightly deviated. However, many present-day wells have long horizontal or nearly-horizontal portions, and the techniques used to measure flow in vertical wells are not applicable to horizontal wells. Moreover, any flow rate measurement technique to be used downhole should take account not only of the several sorts of "lined" wells but also the "barefoot" ones.The invention seeks to satisfy this need for a technique that can be employed with all these sorts of completed well by utilizing a pair of correlated spaced sensors (that can detect "directly" the difference between gas and liquid (oil and/or water), which sensor pair is carried on a logging tool positioned within the borehole itself such that the individual sensors are disposed so as to be actually in the path of any gas bubbles likely to be in the fluid. The correlated output of the sensor pair allows a determination of the gas flow velocity, and if at the same time measurements are taken that provides an indication of the hold-up of the gas bubbles there may by calculation be determined the flow rate both of the gas and of the fluid.
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