The Evaluation and Optimization of ESP Motor Service Life: A Statistical Study for Last 3 Decades for Adiyaman Fields, Turkey
Authors: Ergun Ender , Sahin Mehmet Oguz , Ercelebi Ali Emre 
Published: November 2018

When there is sufficient pressure in the reservoir, the oil come naturally surface. In most cases, artificial lift is needed. The artificial lift supports pressure or extra energy to increase the flow of well fluids to the surface or facility. Examples of artificial lift include rod pumps, gas lift, progressing cavity pump and electrical submersible pumping systems. Artificial lift is needed in wells when there is insufficient pressure in the reservoir to lift the liquid to the surface or facility, however is often used in naturally flowing wells, to raise the flow rate.

The electrical submersible pumping systems deliver an effective and economical means of lifting large volumes of fluids from great depths under a variety of well conditions. Electrical submersible pump has major components such as motor, seal / protector section, intake, pump, downhole monitoring tool electric power cable, surface motor controllers and transformers. Production by electrical submerge pump systems has common used in oil industry and has many advantages like wide flow range, reliability, efficiency, production optimization and etc. In order to sustainable oil production, their service life are so crucial. The purpose of this paper is to outline statistically effects of motor service life to motor loading and motor heating due to tubing failures with field data.

Excessive motor heat affects the motor performance and in the long term its service life. Motor loading causes motor heat so motor loading rate is decisive parameter for motor service life. In this paper, motor loading and its service life were studied according to simple regression analyze in two ways, firstly direct relation and secondly correlated of fluid parameters, such as temperature and water cut. Finally, relation and results between tubing failure and motor service life are investigated.

The Adiyaman fields are located in the southeast of Turkey. The first oil field was discovered in Adiyaman in 1971. Since 1971, more than 45 fields were discovered and 210 MMBOPD was produced. Recoverable oil quantity is 224 MM barrel oil based on reservoir calculations. Recently, even the fact that daily production is more than 190 Mbbl and net crude oil production is more than 9,700 bbl. It shows that 95 per cent of fluid is disposal water. In the Adıyaman district, 279 wells in 40 fields; 99 sucker rod pump wells produce 8,859 bbl/day water and oil (2,145 bbl/day); 95 progressing cavity pump wells produce 47,623 bbl/day water and oil (4,305 bbl/day) and 82 electrical submersible pump wells produce 133,958 bbl/day water and oil (3,940 bbl/day) and 3 artesian wells.

In last 30 years, motor failure rate is 24 per cent in overall 800 electrical submersible pump failures. Motor loading and service life has a meaningful linear relation according to simple regression analysis. Firstly, coefficient of determination, R2, is 0.4013 for motor loading and service life as shown in Graph 1. Secondly, R2 is 0.5336 for motor loading which is correlated of fluid parameters, and service life as shown in Graph 2. According to field data, so as to reach longest service life, motor loading rate should be designed between 75-80 per cent for Adiyaman Fields. While loading of motor is increasing, slip/speed of motor is slightly decreasing. By selecting higher motor power rate, both 1 per cent more production and longer service life could be provided. 13 per cent of motor failures were caused by tubing failure. For this reason to protect motor, downhole monitoring tool should be used. 22 per cent motor failure has tubing failure in previous pull out of hole. For these motors, last mean time between failures is decreasing exponentially. Otherwise, next design, those motors should be rerun in hole with 60-70 per cent motor loading.

Eighty per cent of motor electrical failures are a result of stator winding burnout. (Franklin Aid). Motor rate and type selection is so significant point to support long service life and continuous production. It is important to note that motor temperature rise is a function of horsepower load. According to field data, 60-70 per cent motor loading is best value for Adiyaman Fields, 250 F reservoir temperatures, and 90 per cent water cut to reach longest service life.