| 摘要 |
An ejector pump or jet pump is for use in the drilling of wells in the underground for the production of oil and gas, for example, in which it is the purpose to prevent the total fluid pressure at the bottom of the borehole from reaching a level which constitutes a risk of cracking the rock or sediment being drilled, thus resulting in leakage and circulation failure. For this purpose, the pump is placed between the drill bit and the drill string by means of standard pipe couplings and formed as an elongated cylindrical element with external, longitudinal pump elements with nozzles directed in such a way that low pressure is established externally at the drill bit. The pump is operated by the drilling fluid which is supplied in the normal way from the drill string. The pressure difference across the pump is used to draw a secondary flow of drilling fluid from the established borehole through internal bores in the pump casing to the ordinary nozzles in the drill bit. This fluid flow provides necessary cleaning of the drill bit and drilling surface but, then, will have a highest possible pressure that is limited upwards to the level established in the borehole and so that possible clogging around the drill bit will not cause an increased risk of drilling fluid leaking into the underground.
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