Patent ID: 6155347
Filing Date: 2000-12-05
Classification: E21B

Abstract:
A method for controlling the production rate of a rotary downhole pump to prevent well pump-off, the well having a depth and the pump being driven by a drive string suspended from a drivehead at a wellhead of the well, an annulus being formed between the production tubing and one of the wellbore and the well casing, the pump being positioned in the wellhead at an insertion depth L, comprising the steps of:operating the pump at a first speed less than a maximum rate of the pump until well fluid is produced at the wellhead;continuing operation of the pump at the first speed until the fluid in the annulus has stabilized at a first dynamic fluid level;determining a first static load on the drivehead at the first dynamic fluid level;operating the pump at a second speed higher than the first speed until the fluid level in the annulus has stabilized at a second dynamic fluid level;determining a second static load on the drivehead at the second dynamic fluid level;determining a linear function of the load on the drivehead as a function of the fluid level in the annulus and;reducing the speed of the pump when a critical load on the wellhead is reached which critical load is calculated on the basis of the linear function and corresponds to the level where the fluid level in the annulus is equal to the insertion depth of the pump.