Abstract
Up to 2015, the number of oil wells has reached more than 200,000 for CNPC. It is estimated that conventional beam pumping units are applied to 87% of wells. The traditional pumps suffer from eccentric wear between sucker rod and tubing and high electricity power cost, especially for deviated and horizontal wells. In this paper, we introduced a new artificial lift system, electric submersible progressive cavity pump (ESPCP), to solve these problems.
The new system includes a progressive cavity pump driven by a downhole permanent magnet synchronous motor (PMM), the motor protector and flexible shaft connecting the pump and the motor. In the design no gear reducers is used, which is the most likely failure point, in order to increase the robustness of the system. The motor protector is filled with oil for the lubrication and cooling of the motor. The speed of motor can be adjusted by frequency inverter on the ground from 50 to 500 rpm according to the liquid producing capacity. The operators can remotely control the working state of the system and the running data can be transmitted to the server in the remote office.
We have used the ESPCP systems on 4 troublesome wells for field trials in Jilin oil field. The results show that the system can save more than 20% of the electricity power and double the working life comparing to the traditional beam pumping unit system. Moreover, the system is located at the bottom of oil well, so less site occupation and less noise pollution to the environment are achieved.
The low electricity power and less frequent workover operations can reduce cost especially for the low oil price period. This paper will elaborate on the key learnings based on these field trials.