Frequency-Elastic Operations of Sucker Rod Pumps

The large amount of energy losses along the system of a sucker rod pump is one of the key disadvantages of this artificial lift method, which dictates the energy consumption and drives up operational expenditures for oil producing companies. Therefore, this thesis will give a thorough investigation on the operation and performance of a sucker rod pump. Based on the distribution of polished rod loads and energy consumption, an optimized process is developed that alters the drive speed within each stroke to increase the energy efficiency of the system. The velocity profile is designed with harmonic functions and its implementation requires the installation of a VSD controller. This thesis shows that this method is technically feasible for low to intermediate pumping speeds and leads to several improvements of the sucker rod pumping system. Conventional and optimized operations are simulated and compared with one another, in regards to different pumping speeds, counterweight settings and motor setups. Considering a sample well with an average pumping speed of 5 spm, the peak polished rod loads can be reduced by 2 % and the energy consumption by up to 37 %. This raises the overall efficiency of the system from 24 % to 38 %. Moreover, the loading of the gear reducer and electric prime mover is decreased by up to 23 %. In addition, this thesis will analyse current start-up procedures of sucker rod pumps that are carried out at the beginning of operations or after a well intervention. In virtue of operational and fluid data, an enhanced method is provided, implying a VSD controlled start-up ramp of the pumping speed, to reduce the risks of sand production and immediate equipment failure further.