Analysis of Down Resistance of the Measuring and Adjusting Apparatus in Lubricator of Oilfield Injector

摘要

In the later period of water distribution to increase output of oilfield, it is difficult for the measuring and adjusting apparatus going down in the lubricator when the wellhead pressure reaches to some value, in separate zone injection testing. For this reason, we analyzed its reasons through theoretical derivation and experiments. According to the basic theory of statics of fluid mechanics, we derive and set the mathematical model among the static pressure differential of measuring and adjusting apparatus and the main factors such as wellhead pressure, cable diameter, etc. Indoor experiments and field testing jointly, we set the relationship of wellhead pressure affect the friction between the packing and the cables. The result: down resistance of measuring and adjusting apparatus in lubricator is linear with wellhead pressure and it is square with cable diameter, friction force between the packing and the cables have no big change while the wellhead pressure changes. Through the study of firing resistance, we can calculate the additional weight needed accurately when measuring and adjusting apparatus in lubricator fire and down, and provide theoretical basis for optimizing running parameters and heightening testing efficiency.